JPH087859A - Flat cell and manufacture thereof - Google Patents

Abstract

PURPOSE:To prevent poor shortcircuiting clue to poor insulation by interposing insulating seal materials composed of at least two layers which consist of a layer made of a high polymer high in melting temperature, and of a layer made of thermal plastic resin low in melting temperature, between the circumferential peripheral sections of a positive terminal plate and a negative electrode terminal plate. CONSTITUTION:Insulating seal materials 6 in a window frame shape, that is, a squre ring shape is interposed between the circumferential peripheral sections of a positive electrode terminal plate 4 and a negative electrode terminal plate 5. The insulating seal materials 6 are composed of two laminated layers consisting of three layers formed in such a manner that both surfaces of a polyester film layer 7 which is as thin as 50mum, and has a high melting point of equal to or more than, for example 200 deg.C, are covered with each denaturated polyethylene layer 8 which is as thin as 15mum, and has a ow melting point of 170 deg.C. In this place, a power generation element composed of a positive electrode composite material 2, a negative electrode active material 3 and a separator interposed between these materials, are housed in between a positive electrode terminal plate 4 and a negative electrode terminal plate 5, and the parts of these terminal plates 4 and 5 and the seal materials 6 are fusion bonded at the temperature of 190 deg.C while being pressed with pressure of 3 to 10Kg/cm<2>. These components are then hermetically sealed so as to be formed into the flat type cell.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flat battery used as a power source for thin electronic devices such as IC cards and calculators, and a method for manufacturing the same.

[0002]

2. Description of the Related Art A conventional flat type battery has a structure as shown in FIG.

That is, a separator 10 made of polypropylene nonwoven fabric impregnated with an organic electrolyte is interposed between a positive electrode mixture 11 made of a metal halide, a metal oxide, etc. and a negative electrode active material 12 made of lithium. To form a power generating element, and the power generating element includes a positive electrode terminal plate 13 made of a stainless steel plate having a bulging protrusion in the central portion, a nickel plated stainless steel plate, and the like, and a flat negative electrode terminal plate. It is sandwiched by 14 and. An annular insulating sealing material 15 made of a thermoplastic resin such as modified polyethylene is interposed between the peripheral portions of the positive electrode terminal plate 13 and the negative electrode terminal plate 14. In addition, the periphery of the positive electrode terminal plate 13 and the negative electrode terminal plate 14 seals the power generation element by heat welding by applying a constant pressure while heating at 150 to 200 ° C. (for example, JP-A-59). -83340 publication).

[0004]

Since the flat type battery as described above is mainly used for a card-shaped thin electronic device, the thickness of the battery needs to be about 0.5 mm.
For that purpose, the thickness of the peripheral portions of the positive electrode terminal plate 13 and the negative electrode terminal plate 14 that seal the battery must be about 0.1 mm. Within such a thickness, the thickness between the positive electrode terminal plate and the negative electrode terminal plate is In order to prevent insulation failure, it is preferable to thermally weld and insulate the two with an insulating sealing material made of a thermoplastic resin.

However, the peripheral edge portions of the positive electrode terminal plate and the negative electrode terminal plate, and the insulating sealing material of the thermoplastic resin interposed therebetween are heated at a high temperature of 150 to 200 ° C. for about 50 to 100.
Since it is heat-welded to a thickness of μm, part of the insulating seal material melts too much, or the insulating seal material becomes extremely thin in some areas, so that the thickness of the insulating seal material at the entire peripheral edge of the terminal board is reduced. It is difficult to make them uniform, and as a result, there is a problem that short-circuit defects are likely to occur due to poor insulation between the positive electrode terminal plate and the negative electrode terminal plate after battery assembly.

According to the present invention, a flat type battery which does not cause a short circuit due to poor insulation, and an insulating sealing material which is interposed between the peripheral portions of the positive electrode terminal plate and the negative electrode terminal plate even when heat-sealed has the entire peripheral edge portion. It is an object of the present invention to provide a method for manufacturing a flat type battery that is uniform and does not cause insulation failure.

[0007]

In order to achieve the above object, in the flat battery of the present invention, a power generating element is housed between a positive electrode terminal plate and a negative electrode terminal plate, and the peripheral portions of these terminal plates are accommodated. The insulating sealing material interposed therebetween is formed of at least two layers, that is, a layer made of a polymer material having a high melting temperature and a layer made of a thermoplastic resin having a low melting temperature.

Further, a layer made of a polymer material having a high melting temperature is interposed between layers made of a thermoplastic resin having a low melting temperature, or polyester, polyimide, or fluororesin is used as the polymer material having a high melting temperature. It is effective to use at least one selected from the group containing.

In order to achieve the above object, the method of manufacturing a flat type battery according to the present invention is such that a power generating element is housed between a positive electrode terminal plate and a negative electrode terminal plate, and insulation is provided between peripheral portions of these terminal plates. In a method for manufacturing a flat battery in which a sealing material is interposed and the peripheral portion is heated to heat-seal the sealing material to the terminal plate, a layer made of a polymer material having a melting temperature higher than the heating temperature and the heating temperature are used. An insulating sealing material having at least two layers including a layer made of a thermoplastic resin having a lower melting temperature is interposed between the terminal plates and heated.

[0010]

In the flat type battery configured as described above, when one layer of the thermoplastic resin having a low melting temperature, which constitutes the insulating sealing material, is melted by heating, it melts unevenly. Even if the thickness becomes uneven and a thin portion is formed, the other layer of the polymer material having a high melting temperature remains with a uniform thickness, so that the layer of the thermoplastic resin having a low melting temperature is the peripheral portion of the terminal board. The layer of a polymer material having a high melting temperature can sufficiently function to maintain insulation between the terminal plates.

In addition, even if over-welding is performed, the sealing material is not entirely melted out, and a portion of the material having a high melting temperature remains, so that a short circuit failure does not occur, and an insulating sealing material is formed. When polyester, polyimide, fluororesin, or the like is used for one layer, a uniform layer can be maintained even at 200 ° C. or higher, which is higher than the temperature for heat welding, so that an excellent insulating effect can be secured.

[0012]

Embodiments of the present invention will be described below with reference to FIGS. 1 and 2.

In FIG. 1 showing a cross-sectional view of a main part of a flat type battery and FIG. 2 showing a perspective view of a flat type battery, 1 is a polypropylene nonwoven fabric impregnated with an electrolyte solution containing propylene carbonate containing lithium perchlorate. 2 is a positive electrode mixture containing manganese dioxide as a main component of the active material, which is disposed on the upper surface of the separator 1, 3 is a negative electrode active material made of metallic lithium, which is disposed on the lower surface of the separator 1, and 4 is a protruding portion at the center. Formed on the positive electrode terminal plate made of a stainless steel plate having a thickness of 30 μm; Intervening window frame shape,
That is, it is a square annular insulating sealing material.

The insulating sealing material 6 has a melting point of 200.degree. C. or higher, and both sides of a polyester film (PET) layer 7 having a thickness of 50 .mu.m have a melting point of 170.degree. C. and a modified polyethylene layer having a thickness of 15 .mu.m. Two layers of the sealing material composed of three layers coated with No. 8 are used.

A power generating element 9 comprising a positive electrode mixture 2, a negative electrode active material 3, and a separator 1 interposed therebetween,
It is housed between the positive electrode terminal plate 4 and the negative electrode terminal plate 5, and the portions of these terminal plates 4 and 5 and the insulating sealing material 6 are 3 to 10 kg / cm.
While applying pressure of ² at a temperature of 190 ° C. for 3 to 5 seconds,
It is sealed by heat welding and assembled as a flat battery.

The flat type battery A according to the present invention assembled as described above and the insulating sealing material 15 having the structure shown in FIG.
As a conventional flat type battery B having a melting point of 170 ° C. and a layer of modified polyethylene having a thickness of 80 μm and two layers, 50 batteries each after battery assembly were selected, and a peripheral portion thereof was selected. The average thickness and the number of short-circuited batteries are shown in Table 1.

[0017]

[Table 1]

From Table 1, it can be seen that among the 50 test pieces, the number of short-circuited and defective ones is zero in the case of the flat type battery of the present invention, and 6 in the case of the conventional flat type battery. I understand. This is because from Table 1, in the case of the battery of the present invention, a layer of a polymer material having a melting point higher than the heat welding temperature is present in the insulating seal material, and the seal material can be entirely melted by heat welding. Since the thickness of the peripheral portion of the battery does not become thinner than the thickness of the layer of the polymer material, there is almost no variation in the thickness of the peripheral portion of the battery.

On the other hand, in the case of the conventional battery, the sealing material is melted out by the overheat welding, so that in some batteries, the peripheral edge has a thickness of 100 μm or less and the insulation failure occurs, so that the positive electrode and the negative electrode are separated. This is due to the fact that there was a large variation in the thickness of the peripheral portion of the battery due to contact with the terminal plate and a short circuit.

Although the case where polyester is used as the polymer material has been described, the same effect can be obtained when using polyimide or fluororesin.

[0021]

As described above, according to the present invention, between the positive electrode terminal plate accommodating the power generating element and the peripheral portion of the negative electrode terminal plate,
By interposing an insulating seal material formed of at least two layers, a layer made of a polymer material having a high melting temperature and a layer made of a thermoplastic resin having a low melting temperature, one layer is melted unevenly and the thickness is increased. Even if a thin portion is formed due to non-uniformity, the other layer still has a uniform thickness, so the molten layer acts as a sealing port for the peripheral edge of the terminal plate, and a layer of uniform thickness Since it sufficiently functions to maintain insulation between the plates, the occurrence of short-circuit defects due to insulation defects is eliminated.

In addition, even in the case of overheat welding, the sealing material is not entirely melted out, and the portion of one layer remains, so that the occurrence of short circuit failure is eliminated, and further, in this one layer, polyester, When polyimide, fluororesin, or the like is used, a uniform layer can be maintained even at a high temperature of 200 ° C. or higher and a good insulating effect can be secured.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a main part of a flat battery according to an embodiment of the present invention.

FIG. 2 is a perspective view of the flat battery.

FIG. 3 is a sectional view of a main part of a conventional flat battery.

[Explanation of symbols]

 4 Positive Electrode Terminal Plate 5 Negative Electrode Terminal Plate 6 Insulation Sealing Material 7 Polyester Film Layer 8 Modified Polyethylene Layer 9 Power Generation Element

Claims (4)

[Claims] 1. An insulating seal material for accommodating a power generating element between a positive electrode terminal plate and a negative electrode terminal plate and interposing between the peripheral portions of these terminal plates comprises a layer made of a polymer material having a high melting temperature and a molten material. A flat type battery formed of at least two layers including a layer made of a thermoplastic resin having a low temperature. 2. The flat battery according to claim 1, wherein a layer made of a polymer material having a high melting temperature is interposed between layers made of a thermoplastic resin having a low melting temperature. 3. The flat type battery according to claim 1, wherein the polymer material having a high melting temperature is at least one selected from the group containing polyester, polyimide and fluororesin. 4. A power generating element is housed between a positive electrode terminal plate and a negative electrode terminal plate, and an insulating seal material is interposed between peripheral portions of these terminal plates, and the peripheral portion is heated to seal the sealing material. In a method for manufacturing a flat battery which is heat-welded to a terminal plate, at least two layers of a layer made of a polymer material having a melting temperature higher than the heating temperature and a layer made of a thermoplastic resin having a melting temperature lower than the heating temperature. A method for manufacturing a flat type battery, wherein an insulating sealing material including the above is interposed between the terminal plates and heated.