JP6594738B2 - Film outer battery - Google Patents

Description

  The present invention relates to a film-clad battery, and is capable of fixing a battery element inside a film-shaped packaging material and capable of safely releasing the pressure inside the film-shaped packaging material when gas is generated. It is about.

Lithium ion secondary batteries are useful as a power source for various applications including small portable electronic devices because they have features such as high energy density and low deterioration when repeatedly charged and discharged.
Lithium ion secondary batteries include those using a metal can case that is rigid as a packaging material for enclosing battery elements, and those using a flexible film-shaped packaging material. Power sources for devices that consume a large amount of power, such as various cordless devices such as electric vehicles, hybrid vehicles, and cordless power tools, require large-capacity batteries. A film-clad battery using a film-like packaging material that is advantageous also from the aspect is suitable.

  The film-like exterior material is laminated on the inner surface of a metal foil such as an aluminum foil with a film having good corrosion resistance and heat-sealing property against an electrolyte such as polyethylene or polypropylene, and the outer surface is made of nylon film or polyethylene having high corrosion resistance. A laminated film in which a terephthalate film, a polyimide film, a polyester film or the like is laminated is used.

The film-clad battery is not housed in a rigid packaging material such as a battery can. Therefore, if gas is generated inside the battery due to decomposition of the electrolyte due to overdischarge, etc., As a result, the outer packaging material that has been swollen and can no longer maintain its shape is deformed, and as a result, the battery element may also be deformed or electrode displacement may occur.
For such problems, various measures are taken so that a large problem does not occur by quickly releasing the internal pressure when an unacceptable gas is generated.
For example, Patent Document 1 discloses that an exterior film container having a sealing part joined by fusion of a film-like exterior material, and a safety means that is damaged by being melted by heat generated from a battery in the sealing part. ”(Claim 1) is described.

  Further, in Patent Document 2, “a laminated battery in which at least one separator of the plurality of separators has an insertion portion inserted into the sealing portion of the exterior member” in order to cause the sealing portion to act as a vent. Claim 1) is described.

Further, in the non-aqueous electrolyte secondary battery described in Patent Document 3, as shown by the thin piece 16 in FIG. 2, “the explosion-proof portion in which the thin piece is interposed between the fusible resins is provided, When the internal pressure of the battery package reaches a predetermined value or more, the thin piece can be peeled from the fusible resin (Claim 1). It is only necessary to employ an appropriate metal or resin that has a relatively low peel strength with respect to the film and can set the peel strength to a desired value. ”(Paragraph 0007). Is any one of aluminum, aluminum alloy, titanium, and stainless steel. ”(Claim 2) describes the battery.
These are all proposed to provide explosion-proof properties by a method such as providing a starting point for pressure release operation on the film-shaped exterior material.

JP 2003-242952 A JP 2012-151034 A JP 2001-250526 A

  Although the film-clad battery is excellent in energy density, it is contained in a flexible packaging material, so the battery element is easily deformed by gas generation, etc., so that the battery element is deformed. In such a case, it is essential to quickly release the gas generated inside to the outside.

  The present invention provides a film-clad battery that can quickly release internal pressure and has excellent electrical characteristics and reliability when gas generation or the like occurs in the battery and there is a risk of significant deformation of the battery element. It is a problem to provide.

  An object of the present invention is to have a battery element in which a positive electrode and a negative electrode are alternately stacked via separators, and the battery element is partially fixed to the stacking direction from the top surface to the bottom surface by a stacking fixing tape in the stacking direction. The laminated body fixing tape has a tab portion protruding in the side surface direction of the laminated body, and is a film-clad battery in which the battery element is accommodated in an exterior case made of a film-shaped exterior material, This can be solved by a film-clad battery in which a part is sandwiched and sealed between the sealing parts of the film-like packaging material.

  In the present invention, a part of a side surface of a battery element in which a positive electrode and a negative electrode are laminated via a separator is fixed with a laminated fixing tape from the upper surface to the lower surface of the laminated material, and a part of the laminated fixing tape is fused with a film-like exterior material. When the film-clad battery receives an impact from the outside by sealing between the attachment parts, and the gas is generated inside the battery, the sealing part that is fused by sandwiching the tab part is used. Since the gas inside the battery can be released as a starting point, a highly reliable film-clad battery can be provided.

FIG. 1 is a diagram for explaining one embodiment of the film-clad battery of the present invention. FIG. 2 is a diagram for explaining a conventional film-clad battery.

Hereinafter, embodiments of the present invention will be described in detail.
FIG. 1 is a diagram illustrating an embodiment of a film-clad battery according to the present invention. 1A shows a front view, and FIG. 1B shows a cross-sectional view taken along the line AA in FIG. 1A and enlarged in a direction parallel to the laminated surface. In this figure, the laminated fixing tape is indicated by hatching.
The film-clad battery 1 accommodates a laminate 8 that is a battery element in which a positive electrode 3 and a negative electrode 5 are laminated via a separator 7 in an exterior case made of a film-like exterior material 2, and from the laminate 8 that is a battery element. After the positive electrode terminal 13 and the negative electrode terminal 15 are led out from the film-shaped packaging material 2 to the outside in the same direction, the heat-sealed portion 11 is formed and sealed on the film-shaped packaging material positioned on the outer periphery of the laminate 8. An exterior battery is configured.
The film-clad battery of the present invention is a method in which one film-shaped packaging material is folded and disposed so as to cover both surfaces of the battery element laminate 8 to form the heat-sealed portion 11 and sealed. It can be produced by a method of covering and sealing the battery element laminate 8 with a film-like exterior material.

Further, in order to prevent the positive electrode 3, the negative electrode 5, and the separator 7 constituting the laminated body 8 from being displaced, a part of the side surface of the laminated body 8 of the battery element is laminated and laminated from the upper surface to the lower surface. 9a and 9c are fixed.
And the tab part which protrudes to a side surface direction is provided in at least one part of the lamination | stacking fixing tape 9a, 9c, and it arrange | positions in the heat welding part 11 of the film-form exterior material 2, and is heat-welded integrally with the film-form exterior material 2. .

Moreover, in the film-clad battery of the present invention, the laminated fixing tape is the same material as the constituent material of the heat-sealing surface of the film-like packaging material, and has a melting point of 20 ° C. compared to the material used for the heat-sealing surface. Higher materials are used.
Therefore, the laminated fixing tape and the film-like exterior material have an affinity for each other, and since the melting points are different, they are not compatible and integrated at the temperature at which one resin is melted. A portion having a lower strength than the portion where the exterior materials are thermally welded can be produced. As a result, the portion where the laminated fixing tape is present serves as a safety valve, so that it is possible to improve safety when the internal pressure is increased.

  In addition, a good contact surface is formed as compared with the conventional example in which a metal plate which is a different material is interposed in a synthetic resin to function as a safety valve. Therefore, the joint surface is not torn by the force acting on the laminated fixing tape in normal times, and the function is sufficiently exerted to prevent the positional deviation of the battery laminate, and a large amount of gas such as when the battery reaction is abnormal is generated. When this occurs and the internal pressure rises, it is possible to quickly cleave the film-shaped exterior material and to act as a safety valve.

The film-shaped exterior material 2 has a member having strength and heat resistance such as nylon or polyethylene terephthalate on the surface located on the outer surface side of the laminated battery of aluminum foil, and heat fusion such as polypropylene on the inner surface side. A material obtained by laminating materials having favorable properties can be used.
In addition, a polypropylene having a melting point higher by 20 ° C. or more than the polypropylene forming the inner layer of the film-shaped exterior material can be used for the laminated fixing tape.

Example 1
<Experiment for confirming peel strength of laminated film during film integration>
An exterior film composed of a film of a polyester terephthalate resin 12 μm and a nylon 15 μm layer laminated on the surface of an aluminum foil 40 μm and a polypropylene resin two-layer laminated film of 40 μm on the back surface was used.
Next, at 200 ° C., a part of the 54 μm thick laminated fixing tape is pulled out as a tab and inserted 1 mm into the heat-welded part of the film-like exterior material facing the inner surface of the film-like exterior material at 200 ° C. A test battery was fabricated by heat fusion at a heat welding time of 7.0 sec / heat welding pressure 0.3 MPa.
Next, a peel test of the produced test battery was performed under the conditions of: 180 degree peel / peel speed of 30 mm / min, and Table 1 shows the results.

From the test results of Table 1 above, the film integrated processed product clearly has a 180 degree peel strength lower than that of the normal heat welded product, and the film exterior material heat welded portion is less than 3.0 N / mm. It has been found that the frequency of cleavage is high.
Moreover, it turned out that it can utilize as a gas leak site | part by pinching the film of the samples 1-10 and performing the film integration process heat-processed together with the film-form exterior material.
On the other hand, the peel strength was high under the heat welding processing conditions of Samples 11 to 20, and the function as the target gas leak portion could not be satisfied.

Example 2
Regarding the relationship between the melting point of the laminated fixing tape and the melting point of the heat-welded polypropylene resin layer, when the melting point of the laminated fixing tape is 20 ° C. or higher than the temperature of the heat-welded polypropylene resin layer, It has been found from the experimental results in Table 2 that the peel strength at which the sealed portion is not cleaved, that is, processing to 1.5 N / mm or more is easy.

This result occurs when the melting point of the laminated fixing tape is close to the melting point of the heat-sealing resin layer, and the fusion point of the heat-sealable polypropylene resin layer of the film-like exterior material is uneven and the peel strength varies. To do.
In particular, the weaker one is that the cracks reach between the aluminum foil layer and the heat-welded polypropylene resin layer, and the one that should originally obtain strength by mutual welding of the heat-welded polypropylene resin layer is the aluminum layer and the heat-welded polypropylene resin layer. This causes peeling of the interface.

Increasing the melting point of the laminated fixing tape by 20 ° C. or higher than that of the heat-welded polypropylene resin layer is intended to suppress the occurrence of the fusing point of these spots. That is, in the case of a film-clad battery, if the heat-sealed portion of the film-shaped packaging material is peeled off during normal use where no defects occur, the product cannot be realized. Therefore, this peel strength should not be less than 1.5 N / mm.
In addition, when a material having a melting point of 5 ° C. higher than the melting point of the film-like exterior material is used as the laminated resin tape used as the laminated fixing tape sandwiched between the heat-welded portions of the film-like exterior material, the peel strength reaches 1.5 N / mm. It is unsuitable for use because the frequency of occurrence of non-existing items increases.
In the present invention, as a synthetic resin used as a laminated fixing tape, by using a material whose melting point is 20 ° C. or higher than the melting point of the film-shaped exterior material, sufficient peel strength that does not fall below 1.5 N / mm is obtained. The present invention has been completed by finding conditions that can always be obtained.

  DESCRIPTION OF SYMBOLS 1 ... Film exterior battery, 2 ... Film-shaped exterior material, 3 ... Positive electrode, 5 ... Negative electrode, 7 ... Separator, 8 ... Laminated body of battery elements, 9a, 9c ... Laminated fixing tape 11 ... Heat fusion part, 13 ... Positive terminal, 15 ... Negative terminal, 16 ... Flame

Claims (2)

The battery element has a battery element in which a positive electrode and a negative electrode are alternately stacked via a separator, and a part of the side surface in the stacking direction is fixed by a stacking fixing tape from the upper surface to the lower surface in the stacking direction,
The laminated fixing tape has a tab portion protruding in the side surface direction of the laminated body,
A film-covered battery in which the battery element is housed in an exterior case made of a film exterior material,
A film-clad battery, wherein a part of the tab part is sandwiched and sealed between sealing parts of a film-clad material.   2. The film-clad battery according to claim 1, wherein a synthetic resin tape having a melting point of the laminated fixing tape of 20 ° C. or more higher than a melting point of a synthetic resin used as a heat-sealing layer of the film-clad material is used.

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