WO2005122294A1

WO2005122294A1 - Electric device packed in film

Info

Publication number: WO2005122294A1
Application number: PCT/JP2005/010843
Authority: WO
Inventors: Hiroshi Yageta
Original assignee: Nec Corporation
Priority date: 2004-06-14
Filing date: 2005-06-14
Publication date: 2005-12-22
Also published as: JPWO2005122294A1; JP4876915B2

Abstract

A releasing pressure can be easily set for inner pressure increase due to gas generation, without deteriorating sealing reliability of an electric device element. A battery (1) packed in a film is provided with a battery element (2) and a packing film (5) for packing the battery element (2). The packing film (5) is a laminated film provided by laminating a non-breathable layer composed of a metal foil and a heat sealing layer composed of a heat sealing resin. The heat sealing layers are faced and are heat-sealed in the periphery of the battery element (2) to seal the battery element (2). In a part of a sealed area (5a) formed by heat-sealing the packing film (5), a nonwoven cloth (8) is sandwiched between the facing packing films (5), and the heat sealing resin is spread in the fiber of the nonwoven cloth (8).

Description

Specification

Film-covered electrical device

Technical field

The present invention relates to a film-covered electric device in which electric device elements such as a battery element and a capacitor element, such as a chemical battery element and a capacitor element, are sealed with a film material.

Background art

[0002] Conventionally, as a film-covered battery using a film as a packaging material, a battery element is surrounded by a laminated film in which a metal layer and a heat-sealing resin layer are laminated, and a positive electrode and a negative electrode connected to the battery element. The battery element is hermetically sealed (hereinafter simply referred to as “sealing”) by heat-sealing the open edge of the laminate film with the lead of the battery pulled out from the laminate film. Being done.

[0003] As in the case of using other types of exterior materials, a battery using a film as an exterior material does not cause outside air to enter the inside of the battery or leak of electrolyte in the battery, as shown in Fig. It is required that the sealing reliability at the heat-sealed part be ensured. In particular, sealing reliability is important for batteries containing non-aqueous electrolyte (hereinafter also referred to as “non-aqueous electrolyte batteries”). If there is poor heat fusion, the electrolyte deteriorates due to the components of the outside air, and the battery performance is significantly reduced.

[0004] By the way, when a voltage outside the specified range is applied to the battery during use of the battery, gas species may be generated due to electrolysis of the electrolyte solvent. In addition, even if the battery is used at a high temperature outside the specified range, substances that are the source of gas are generated by decomposition of the electrolyte salt. Basically, it is ideal to use batteries within the specified range so that no gas is generated. However, if the battery control circuit fails for some reason and abnormal voltage is applied, or if the surroundings become abnormally high for some reason, a large amount of gas may be generated in some cases.

[0005] The generation of gas inside the battery causes an increase in the internal pressure of the battery. In order to prevent the battery from exploding due to an extremely high internal pressure, many batteries that use metal cans as exterior materials have a pressure relief valve that allows gas to escape to the outside of the battery when the internal pressure of the battery increases. ing . However, it is structurally difficult to provide a pressure relief valve in a film-covered battery using a film as a cover material. In the case of a film-covered battery, if the internal pressure rises too much, the film expands, and eventually the film bursts and gas is ejected at that location, but it is not possible to specify where the burst occurs. Therefore, depending on the location of the rupture, it may adversely affect surrounding equipment and members.

[0006] Therefore, in the case of conventional film-covered batteries, several pressure relief structures have been proposed to solve the problems caused by the generation of gas inside the battery!

[0007] Japanese Patent Application Laid-Open No. 2001-93489 (Patent Document 1) discloses a film-covered battery in which a multilayer sheet is interposed in a part of a sealing portion of a package film. The multilayer sheet is obtained by laminating a resin film having sufficient heat-fusibility with the exterior film on both sides of a resin film having a lower melting point than the heat-fusible resin layer of the exterior film. At an abnormally high temperature or the like, the inner layer of the multilayer sheet is melted and melted, thereby releasing gas generated inside the battery. Japanese Patent No. 2725881 (Patent Document 2) discloses that a sheet-like member having a higher melting point than the heat-fusible resin layer of the exterior film is sandwiched in a part of the sealing portion of the exterior film, A film-covered battery in which an outer film is in an unfused state in a region where this member is interposed is disclosed. Japanese Patent Application Laid-Open No. H11-86823 (Patent Document 3) discloses a film-covered battery in which at least a part of a sealing portion of a covering film is provided with a sealing means having low pressure resistance. As the sealing means, a sealing portion which is heat-sealed under a heat-sealing condition such that the peel strength becomes a predetermined value, or a shape obtained by making a material of a fusion bonding material or an adhesive different from other portions. An example of the formed sealing portion is shown in FIG.

Disclosure of the invention

[0008] However, while the pressure release structure disclosed in Patent Document 1 is a structure in which the pressure inside the battery is released by softening and melting the inner layer of the multilayer sheet, the release pressure depends on the temperature and the inner layer. It depends on the melting point of the constituent resin film, and it is difficult to arbitrarily adjust the opening pressure. Further, in the pressure release structure disclosed in Patent Document 2, since the member sandwiched between the sealing portions is sheet-shaped, the exterior material is not joined in the region where the member is sandwiched, and the sealing reliability is reduced. It will be extremely low. Further, in the pressure release structure disclosed in Patent Document 3, as described above, the conditions for heat fusion are changed, and The material of the adhesive is different from other parts. However, when the heat fusion conditions are changed, even if the heat fusion conditions are changed, the fusion strength of the exterior material does not change so much, and it is difficult to arbitrarily adjust the opening pressure. On the other hand, even when the material of the bonding material or the adhesive is different from the other parts, since the opening pressure depends on the material of the bonding material or the adhesive, it is not necessary to arbitrarily adjust the opening pressure. Have difficulty.

[0009] The above is a problem common to not only batteries but also film-covered electric devices in which electric device elements that may generate gas are sealed with an external film.

[0010] An object of the present invention is to provide a film-covered electric device that can easily set an opening pressure at the time of film expansion due to generation of a gas in an abnormal state without lowering the sealing reliability of an electric device element. It is.

[0011] In order to achieve the above object, the film-covered electric device of the present invention has a structure in which an electric device element and at least a heat-sealing layer made of a heat-fusible resin and a non-venting layer are laminated. And The sealing film surrounds the electric device elements with the heat-sealing layer as the inner surface, and the heat-sealing layers facing each other around the heat-sealing layer are heat-sealed to form a sealing region for sealing the electric device elements. Have been. At least one sheet-shaped member made of a resin having a melting point higher than that of the heat-fusible resin is sandwiched in a part of the sealing region in a space between the facing exterior films and surrounding the electric device. It is arranged to be exposed to. The sheet-like member has a structure in which the molten heat-fusible resin can penetrate, and the heat-fusible resin permeates the sheet-shaped member.

[0012] In the film-covered electric device of the present invention configured as described above, at least a part of the sheet-shaped member is sandwiched between the facing outer films in a part of the sealing region. The sheet-shaped member has a structure through which the molten heat-fusible resin can penetrate. However, the resin constituting the sheet-like member is melted by heat fusion for forming a sealing region having a higher melting point than the heat-fusible resin constituting the heat-sealing layer of the exterior film. Absent. Therefore, the peeling strength of the portion where the sheet-like member is sandwiched in the sealing region is smaller than that of the other portions, and this portion can be preferentially peeled when the internal pressure rises, and the pressure can be released. The heat-sealing resin can penetrate into the sheet member by the heat-sealing of the exterior film, and the sealing reliability does not decrease even if the structure is interposed with the sheet member. Yes. Since the peel strength at the portion where the sheet-shaped member is sandwiched depends on the degree of penetration of the heat-fusible resin of the sheet-shaped member, the penetration degree of the heat-fusible resin should be appropriately selected. Thereby, the peeling strength at the portion where the sheet-like member is sandwiched, that is, the opening pressure can be arbitrarily set.

[0013] As the sheet-like member, a fiber aggregate represented by a nonwoven fabric, a microporous film, or the like can be used.

[0014] By stacking a plurality of sheet-like members, an effect of reducing the peel strength can be obtained as compared with the case where one sheet-like member is used. Therefore, when a smaller peel strength is required, it is preferable to sandwich a plurality of sheet-like members in an overlapping manner.

[0015] Furthermore, in a region where the sheet-shaped member is sandwiched, a pressure release portion is provided for communicating the inside of the space surrounding the electric device element with the outside air by peeling the exterior film in this region. When the process reaches the pressure release section, the pressure is released. Therefore, by appropriately setting the position of the pressure release portion, the degree of freedom in setting the release pressure is increased. The pressure release portion can be, for example, a hole or cut formed in at least one of the facing films in the sealing region.

According to the present invention, a very simple configuration in which a sheet-like member having a structure through which molten heat-fusible resin can penetrate is sandwiched between facing exterior films in a part of the sealing region, The opening pressure can be easily and reliably set without lowering the sealing reliability of the electric device element.

Brief Description of Drawings

FIG. 1 is an exploded perspective view of a film-covered battery according to one embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view of the film-covered battery shown in FIG. 1 at a portion where a nonwoven fabric is sandwiched, along a longitudinal direction of a sealing region.

FIG. 3A is a view showing an example of an arrangement direction of nonwoven fabric fibers sandwiched between sealing regions.

FIG. 3B is a view showing another example of the arrangement direction of the fibers of the nonwoven fabric sandwiched between the sealing regions.

FIG. 4 is a schematic cross-sectional view along a longitudinal direction of a sealing region at a portion where the nonwoven fabric is sandwiched when two nonwoven fabrics are sandwiched.

[FIG. 5] Another example of a nonwoven fabric to be sandwiched, showing a sealed region at a portion where the nonwoven fabric is sandwiched. FIG.

[6] FIG. 6 is a plan view of a sealing region in a portion where the nonwoven fabric is sandwiched in a case where a through hole is added to a portion where the nonwoven fabric is sandwiched.

[7] FIG. 7 is a plan view showing a modified example of the example shown in FIG. 6, showing a sealing region at a portion where a nonwoven fabric is sandwiched.

FIG. 8 is a plan view of a sealed region in a portion where a nonwoven fabric is sandwiched in a film-covered battery according to another embodiment of the present invention.

[9] FIG. 9 is a perspective view for explaining a peeling stress acting when the boundary of the heat-sealed portion of the exterior film has no unevenness.

[10] FIG. 9 is a perspective view illustrating a peeling stress acting on the protruding portion shown in FIG. [11] FIG. 9 is a plan view showing the progress of peeling at the protruding portion shown in FIG.

Explanation of symbols

1 Battery with battery

2 Battery element

3 Positive lead

4 Negative electrode lead

5 Exterior film

5a Sealed area

5b Cup part

6 Thermal fusion layer

7 Non-breathable layer

8 Non-woven fabric

9 Fiber

10 Through hole

11 Non-fused part

12 Projection

BEST MODE FOR CARRYING OUT THE INVENTION

Referring to FIG. 1, a flattened structure having a structure in which a plurality of positive electrodes and a plurality of negative electrodes are stacked The battery element 2 having a substantially rectangular parallelepiped shape, the positive electrode lead 3 and the negative electrode lead 4 connected to the positive electrode and the negative electrode of the battery element 2, respectively, and a part of the positive electrode lead 3 and the negative electrode lead 4 are extended to form the battery element 2. A film packaged battery 1 according to an embodiment of the present invention having a package film 5 to be sealed is shown.

[0020] In the battery element 2, a plurality of positive electrodes and a plurality of negative electrodes each made of a metal foil having both surfaces coated with an electrode material are alternately stacked via a separator. Each positive electrode and each negative electrode has an uncoated portion on which no electrode material is applied. The non-applied portion is also provided so that one side force of each positive electrode and each negative electrode also protrudes. The non-coated portions of the positive electrode and the non-coated portions of the negative electrode are collectively ultrasonically welded and connected to the positive electrode lead 3 and the negative electrode lead 4, respectively. The positive electrode and the negative electrode are overlapped with the non-coated portion of the electrode material protruding in the opposite direction. Therefore, the positive electrode lead 3 and the negative electrode lead 4 are drawn out from the sides of the film-covered battery 1 facing each other. In this embodiment, the planar shape of the film-covered battery 1 is substantially rectangular, and the positive electrode lead 3 and the negative electrode lead 4 are drawn out from short sides of the rectangle.

In the case of a non-aqueous electrolyte battery such as a lithium ion battery, an aluminum foil is used for a metal foil constituting a positive electrode, and a copper foil is used for a metal foil constituting a negative electrode. An aluminum plate is used for the positive electrode lead 3, and a nickel plate or a copper plate is used for the negative electrode lead 4. When the negative electrode lead 4 is made of a copper plate, its surface may be plated with nickel.

For the separator, a sheet-like member that can be impregnated with an electrolyte, such as a microporous film (microporous film), a nonwoven fabric, or a woven fabric, made of a thermoplastic resin such as polyolefin is used. be able to. For microporous films, a dry process in which fine holes are formed in the film by uniaxially or biaxially stretching the film, or a film is formed by melting and kneading a base polymer with a solvent or fine particles, and then immersion in a solvent Alternatively, it can be produced by a production method such as a wet process in which a solvent or fine particles are extracted by volatilization, and if necessary, further stretched to form a porous film.

The exterior film 5 is formed by two sheets of lamination surrounding the battery element 2 sandwiching the battery element 2 from both sides in the thickness direction, and heat-fusing the opposing surfaces overlapping each other around the battery element 2 to form a battery. Element 2 is sealed. Figure 1 shows the area of the exterior film 5 that is to be heat-sealed. The stop area 5a is indicated by oblique lines. The exterior film 5 has a cup portion 5b in a central region in order to form a battery element storage portion which is a space surrounding the battery element 2. The sealing region 5a is formed all around the cup portion 5b. The processing of the cup portion 5b can be performed by deep drawing. In the example shown in FIG. 1, the cup portion 5b is formed on both the outer films 5, the force cup portion may be formed on only one of them, or the outer film 5 may be formed without forming the cup portion. The battery element 2 may be surrounded by utilizing the flexibility of the above.

[0024] As a laminate film constituting the exterior film 5, if the battery element 2 is flexible and can seal the battery element 2 by heat fusion so as to prevent electrolyte solution from leaking, this type of laminate film is used. A film generally used for a film-covered battery can be used. A typical layer configuration of the laminate film used for the exterior film 5 is a configuration in which a non-venting layer made of a metal thin film and the like and a heat-sealing layer made of a heat-fusible resin are laminated, or a non-venting layer is used. There is a configuration in which a protective layer made of a film such as polyester or nylon such as polyethylene terephthalate is further laminated on the surface of the layer opposite to the heat-sealing layer. When sealing the battery element 2, the battery element 2 is surrounded by the heat-sealing layers facing each other.

As the metal thin film constituting the non-ventilated layer, for example, a foil of Al, Ti, Ti alloy, Fe, stainless steel, Mg alloy, or the like having a thickness of 10 m to L00 m can be used. The heat-fusible resin used for the heat-sealing layer is not particularly limited as long as it is a heat-fusible resin.Examples include polypropylene, polyethylene, acid modified products thereof, polyphenylene sulfide, and polyolefin. Polyesters such as ethylene terephthalate, polyamides, ethylene butyl acetate copolymer and the like can be used. The thickness of the heat-sealing layer is preferably from 30 m to 100 m, more preferably from 10 m to 200 m.

[0026] In a part of the sealing region 5a, a nonwoven fabric 8 sandwiched between the exterior films 5 sandwiching the battery element 2 and exposed in the battery element storage portion is formed by heat of the exterior films 5 with each other. It is held by fusion. The nonwoven fabric 8 is made of a resin having a melting point higher than the melting point of the heat-fusible resin constituting the heat-fusible layer of the exterior film 5 and different from the heat-fusible resin of the exterior film 5. It is a thing. For example, when the heat-fusible resin constituting the heat-sealing layer of the exterior film 5 is polypropylene, the nonwoven fabric 8 is made of polyethylene terephthalate. Can be used.

The heat-sealing of the exterior films 5 is performed at a temperature higher than the melting point of the heat-fusible resin constituting the heat-sealing layer of the exterior film 5 and lower than the melting point of the resin constituting the nonwoven fabric 8. Do with. As a result, the heat-fusible layer 6 melts, but the fibers 9 of the nonwoven fabric 8 do not melt, so that the heat-fusible resin of the heat-fusible layer 6 permeates between the fibers 9 of the nonwoven fabric 8 as shown in FIG. Then, the nonwoven fabric 8 is embedded and held in the heat sealing layer 6 of the exterior film 5. FIG. 2 schematically shows a cross section of a side of the sealing region 5a in which the nonwoven fabric 8 is sandwiched in FIG. 1 along the longitudinal direction. In the state where the sealing region 5a is formed, as shown in FIG. 2, the heat-sealing layers 6 of the two external films 5 are united by heat-sealing. In FIG. 2, the layer outside the heat-sealing layer 6 is the non-venting layer 7 of the exterior film 5.

[0028] The structure in which the nonwoven fabric 8 is sandwiched between the facing films 5 facing each other in the sealing region 5a can be manufactured, for example, as follows. First, a nonwoven fabric 8 cut in advance to a predetermined size is placed on a portion to be the sealing region 5a of one of the two exterior films 5, and the adhesive or the heat-sealing layer 6 is slightly softened. The nonwoven fabric 8 is temporarily fixed to the exterior film 5 by heat fusion at a low temperature. The temporary fixing is not required to firmly fix the nonwoven fabric 8 to the exterior film 5, but may be sufficient to hold the nonwoven fabric 8 on the exterior film 5 until the sealing region 5 a is finally formed. Next, the battery element 2 to which the positive electrode lead 3 and the negative electrode lead 4 are connected is mounted on the outer film 5 on which the nonwoven fabric 8 is temporarily fixed, and another outer film 5 is further covered therefrom. The outer film 5 is heat-sealed around the entire circumference. As described above, the heat fusion temperature at this time is higher than the melting point of the heat-fusible resin constituting the heat-fusible layer 6 of the exterior film 5 and higher than the melting point of the resin constituting the nonwoven fabric 8. Use a low temperature. As a result, the heat-sealed portion of the exterior film 5 becomes the sealing region 5a, and the film exterior battery 1 having the nonwoven fabric 8 interposed in a part thereof is obtained.

[0029] In the film-covered battery 1 configured as described above, gas is generated from the battery element 2 due to, for example, application of a voltage out of the specification range or temporary high temperature during use. Then, the internal pressure of the film-covered battery 1 increases. When the internal pressure increases, the battery element housing portion, which is a space surrounded by the cup portion 5b of the exterior film 5, tries to expand in a dome shape, and a peeling stress acts on the inner edge of the sealing region 5a. [0030] A nonwoven fabric 8 is sandwiched in a part of the sealing region 5a, and in the portion where the nonwoven fabric 8 is sandwiched, as shown in FIG. The resin is soaked between the fibers 9 of the nonwoven fabric 8. Therefore, the heat-sealing layer 6 has heat-fusible resin continuously above and below the non-woven fabric 8 even though the non-woven fabric 8 is interposed therebetween, which is different from the case where a sheet-like member is sandwiched. The heat-fusible resin is not divided in the thickness direction of the heat-fusible layer 6. Therefore, the sealing performance required for the sealing region 5a can be obtained.

Further, by sandwiching the nonwoven fabric 8, in the region where the nonwoven fabric 8 is sandwiched, the bonding region between the heat-fusible layers 6 of the respective exterior films 5, that is, the heat-fusible resin is continuously connected. When the non-woven fabric 8 having the same area is sandwiched, the area becomes smaller than that of the other areas. The nonwoven fabric 8 is made of a resin having a different melting point and a higher melting point than the heat-fusible resin constituting the heat-fusible layer 6. Adhesive strength to fat is smaller than adhesive strength between heat-fusible resins.

[0032] Thus, the portion where the nonwoven fabric 8 is sandwiched can be peeled off with a small peeling stress as compared with the other sealing region 5a. Therefore, when the peeling force acts on the sealing region 5a, the peeling of the exterior film 5 in the sealing region 5a proceeds preferentially in the portion where the nonwoven fabric 8 is sandwiched. When the peeling of the package film 5 progresses and reaches the outer edge of the sealing region 5a, the battery element housing communicates with the outside (outside air) of the film package battery 1, whereby the increased pressure is released. Therefore, a specific positional force gas can be ejected before the film-covered battery 1 ruptures, so that the rupture of the film-covered battery 1 and ejection of gas in an unintended direction can be prevented.

The peel strength of the sealing region 5 a depends on the proportion of the heat-fusible resin in the heat-fusible layer 6. If this proportion is high, the peel strength tends to be high, and if the proportion is low, the peel strength tends to be low. On the other hand, the proportion of the heat-fusible resin in the heat-fusible layer 6 depends on the basis weight of the nonwoven fabric 8 to be sandwiched. If the basis weight is large, the proportion of the heat-fusible resin is low. If the basis weight is small, the proportion of the heat-fusible resin tends to be high. As described above, the peel strength in the region where the nonwoven fabric 8 is sandwiched can be adjusted by appropriately setting the basis weight of the nonwoven fabric 8 to be sandwiched. Low peel strength means that the gas can be released at a lower internal pressure. Thus, sandwich the nonwoven fabric 8 By adopting a structure in which the peel strength is adjusted, the basis weight of the nonwoven fabric 8 can be appropriately set, and the gas release pressure can be arbitrarily set.

[0034] Further, by using a non-woven cloth 8, which is an aggregate of fibers 9, as a member to be sandwiched between the parts from which gas is to be released, different types of seals, such as those found in a conventional oil-sandwiched safety valve structure, can be obtained. Unlike the case where the fat is apparently adhered to the flat interface, it is necessary to balance the long-term reliability of the adhesiveness to the electrolyte, which is an organic solvent, and the ease of operation that can be operated with a small force in the event of an abnormality. it can.

[0035] As the nonwoven fabric 8 to be sandwiched, any of a wet type, a dry type (fat adhesion, thermal bond, spunlace) and a spun bond type (melt spinning, wet spinning, flash spinning, melt blowing) may be used. In the nonwoven fabric 8, there are fibers in which fibers 9 are arranged in almost one direction and those in which fibers 9 are randomly arranged.For adjusting the peel strength, the ratio of the fibers 9 in the heat-fused layer 6 is determined. Closely related, the arrangement of the fibers 9 is not so important. Therefore, for example, as shown in FIG.3A, the nonwoven fabric 8 may be sandwiched so that the fibers 9 are arranged from the outer edge to the inner edge of the sealing region 5a substantially in parallel with the direction of force, or as shown in FIG.3B. The nonwoven fabric 8 may be sandwiched so that the fibers 9 are arranged in a direction substantially perpendicular to the direction from the outer edge to the inner edge of the sealing region 5a. Of course, the arrangement direction of the fibers 9 may be different from these. Here, the inner edge of the sealing region 5a is an edge on the battery element 2 side, and the outer edge is an edge on a side remote from the battery element 2.

[0036] As described above, in order to lower the opening pressure, the basis weight of the nonwoven fabric 8 to be sandwiched may be increased. However, there is a limit in reducing the opening pressure with a single nonwoven fabric 8 alone. In addition, since the thickness of the nonwoven fabric 8 generally increases in accordance with the basis weight, if the thickness of the nonwoven fabric 8 is excessively large in order to obtain a desired basis weight, heat is not generated during heat fusion. There is a possibility that the adhesive resin does not sufficiently penetrate between the fibers 9 of the nonwoven fabric 8 and the sealing reliability is impaired. Therefore, when a lower opening pressure is required, it is preferable to sandwich two nonwoven fabrics 8 one on top of the other, as shown in FIG.

[0037] By stacking two nonwoven fabrics 8, the peel strength is made smaller than when one nonwoven fabric 8 having the same basis weight as the total basis weight of the two nonwoven fabrics 8 is sandwiched. be able to. This is because the two nonwoven fabrics 8 overlap each other, so that This is presumably because the area where the heat-fusible resin permeated through the woven fabric 8 is connected becomes smaller, and the bonding area between the heat-fusible resins becomes smaller than in the case of a single nonwoven fabric 8. The number of the nonwoven fabrics 8 to be superimposed is not limited to two, but if it is necessary to set a lower opening pressure than it is, three or more nonwoven fabrics can be used.

[0038] The shape and size of the nonwoven fabric 8 are not particularly limited as long as the shape and size of the nonwoven fabric 8 have a portion extending from the outer edge to the inner edge of the sealing region 5a! FIG. 1 shows the force of a rectangular nonwoven fabric 8 .For example, the trapezoidal shape shown in FIG. 5, the inner edge length L1 of the nonwoven fabric 8 is longer than the outer edge length L2, and the battery element 2 side edge to the outer edge The nonwoven fabric 8 may be shaped such that the size decreases as the force increases. Thereby, the shape of the nonwoven fabric 8 becomes a shape according to the progress of the peeling, so that the peeling can proceed smoothly. Here, the inner edge and the outer edge of the nonwoven fabric 8 are, similarly to the inner edge and the outer edge of the sealing region 5a described above, an edge on the battery element 2 side and an outer edge on the side away from the battery element 2. Also in this case, the number of the nonwoven fabrics 8 to be sandwiched is not limited to one, and a plurality of nonwoven fabrics can be used.

Further, as shown in FIG. 6, a through-hole 10 that penetrates through the exterior film 5 can be formed as a pressure release part in a region where the nonwoven fabric 8 is sandwiched in the sealing region 5a. By forming the through-hole 10, when the progress of the peeling reaches the through-hole 10, the inside of the battery element housing communicates with the outside air, and the pressure can be released. The opening pressure can also be adjusted by adjusting the position of the through hole 10, and the adjustment of the position of the through hole 10 is easier than the adjustment of the basis weight of the nonwoven fabric 8. By providing such a through hole 10, the opening pressure can be adjusted more accurately.

When the through-hole 8 is formed in the region where the nonwoven fabric 8 is sandwiched, the pressure is released when the peeling reaches the through-hole 10, so that the peeling does not proceed outside the through-hole 10. . Therefore, when the through hole 10 which is a pressure release portion is provided, as shown in FIG. 7, the width W1 of the nonwoven fabric 8 is made smaller than the width W2 of the sealing region 5a, and the outer edge 8b of the nonwoven fabric 8 is sealed. Even if it is located inside the outer edge of the stop region 5a, the substantial opening pressure does not change. In addition, this allows the size of the nonwoven fabric 8 to be reduced, and the amount of the nonwoven fabric 8 to be used can be reduced. The width of the nonwoven fabric 8 and the sealing region 5a means a length in a direction from the outer edge to the inner edge of the sealing region 5a. 6 and 7, the shape of the nonwoven fabric 8 is arbitrary. Yes, for example, the shape shown in FIG. 5 can be used, and the number of nonwoven fabrics 8 to be sandwiched can be not only one but also a plurality of nonwoven fabrics.

FIGS. 6 and 7 show an example in which the through hole 10 is provided as the pressure release portion, but the pressure release portion does not need to be the through hole 10. For example, the same effect can be obtained by forming a cut in the non-woven fabric 8 halfway in the region where the non-woven fabric 8 is sandwiched from the outer edge to the inner edge of the sealing region 5a. In this case, the opening pressure can be arbitrarily adjusted depending on the position of the tip of the cut. In addition, the pressure release portion does not need to have a structure that penetrates two overlapping exterior films.The same effect can be obtained even if a through hole or cut is formed in only one of the two exterior films that overlap. can get.

[0042] In the above-described embodiment, the shape of the force sealing region 5a itself, which is an example in which the sealing region 5a is formed with a constant width, is changed to a shape in which the peeling stress is likely to act locally, and the nonwoven fabric 8 is formed. Can be more effectively exerted. Fig. 8 shows an example.

In the example shown in FIG. 8, the exterior films facing each other are thermally fused to the edge of the sealing region 5a on the battery element 2 side, that is, the two non-fused portions 11 However, it is formed in a cove shape continuously with the battery element storage section. The two non-fused portions 11 are spaced from each other in the direction along the peripheral edge of the sealing region 5a, so that the region between the non-fused portions 11 becomes the battery element housing portion. The protruding portion 12 protrudes toward the front. The nonwoven fabric 8 is located at the projecting portion 12, and the facing outer film is heat-sealed at the projecting portion 12 via the nonwoven fabric 8. Further, a through hole 10 which is a pressure release part is formed in the protruding part 12.

As described above, by providing the protruding portion 12 that protrudes toward the battery element storage portion in the sealing region 5a, the internal pressure of the film-covered battery increases due to generation of gas from the battery element 2. At this time, the bowing I peeling stress of the exterior film in the sealing region 5a acts intensively on the protrusion 12, and the peeling of the exterior film proceeds preferentially at the protrusion 12. When the peeling reaches the position of the through hole 8 as the internal pressure increases, the battery element housing communicates with the outside of the film-covered battery, and the increased pressure is released through the through hole 8.

[0045] Hereinafter, the progress of peeling of the exterior film due to an increase in internal pressure will be described in detail.

When the boundary between the heat-sealed region and the non-heat-sealed region of the exterior film has a shape without unevenness, as shown in FIG. 9, the peeling stress F1 is one-way. Only for The peeling proceeds toward the outer edge of the exterior film 5.

However, when the protruding portion 12 is provided as described above, the non-fused portion 11 exists on both sides of the protruding portion 12, and the non-fused portion 11 is also filled with gas as shown in FIG. As a result, the exterior film 5 swells on both sides of the protruding portion 12, so that the protruding portion 12 is subjected to a peeling stress F2 on the side edge in addition to the peeling stress F1 acting on the tip. Therefore, a peeling stress greater than that of the other portions acts on the corners of the protruding portion 12 as these resultant forces, and the peeling of the exterior film 5 proceeds at the corners in preference to the other portions. When the outer film 5 peels off at the corners, the corners are rounded, but the projections 12 still maintain a convex shape, and the projections 12 are subjected to peeling stress from a plurality of directions. Therefore, the peeling of the exterior film 5 has a lower priority than the other portions, while reducing the sharpness of the convex shape and finally until the projection 12 is almost eliminated. Progress.

FIG. 11 shows the progress of peeling of the exterior film 5 at the protruding portions 12. As shown in FIG. 11, in the protruding portion 12, peeling proceeds from both sides of the protruding portion 12 as a → b → c as the internal pressure increases. The peeling position of the exterior film 5 depends on the material of the exterior film 5, the width Wp of the projection 12, the projection length L of the projection 12, and the internal pressure. Therefore, if the material of the outer film 5, the width Wp of the protruding portion 12, and the protruding length L of the protruding portion 12 are determined in advance, by adjusting the position of the through hole 8, the inside and outside of the battery element housing portion can be adjusted. The opening pressure, which is the internal pressure of the battery element housing when the communication is established, can be arbitrarily set. In other words, if the through hole 8 is provided at a position near the tip of the protruding portion 12, the pressure can be released at a low internal pressure, and if the through hole 8 is provided near the base of the protruding portion 12, the pressure can be increased to a high internal pressure. Do not open.

[0049] By providing the protruding portion 12 in the sealing region 5a as described above, the protruding portion 12 functions as a stress concentration portion when the internal pressure of the exterior film battery increases. As a result, by sandwiching the nonwoven fabric 8 between the protruding portions 12, this function of the protruding portions 12 and the above-described operation and effect of the nonwoven fabric 8 can be combined to more reliably and easily control the opening pressure. .

The shape and the like of the stress concentration portion provided in the sealing region 5a are not limited to those shown in FIG. 8, as long as the peeling stress can act in a concentrated manner. For example, in FIG. 8, if the shape of the protruding portion 12 is substantially protruding toward the battery element 2, if the shape thereof is tapered, Any shape, such as one having an arc-shaped tip, can function as a stress concentration portion. Further, the non-fused portion 11 may be provided in an island shape independently of other heat-fused portions, or may be provided so as to protrude from the inner edge of the sealing region 5a without providing the non-fused portion 11. Is also good. In any case, the nonwoven fabric 8 is sandwiched between the facing outer films at the stress concentration portion, and a pressure release portion is provided in this portion.

[0051] In order for the peeling to proceed effectively in the region where the nonwoven fabric 8 is sandwiched, the nonwoven fabric 8 is sandwiched at a position where the internal pressure due to the gas generated in the battery housing is most likely to act. For this purpose, as shown in FIG. 1, of the sides around the film-covered battery 1, the long side from which the positive electrode lead 3 and the negative electrode lead 4 are not drawn out is approximately at the center in the direction along that side. Preferably, the nonwoven fabric 8 is sandwiched between the portions.

Although the present invention has been described with reference to some typical examples, it is apparent that the present invention is not limited to these but can be appropriately modified within the scope of the technical idea of the present invention. It is.

For example, in the above-described example, an example is shown in which a nonwoven fabric is used as the sheet-like member disposed between the facing exterior films in the sealing region. The nonwoven fabric is not limited to a nonwoven fabric as long as it is made of a resin having a higher melting point than the heat-fusible resin constituting the fusion-bonding layer and has a structure through which the melted heat-fusible resin can penetrate. Examples of such a sheet-like member include a fiber aggregate, a microporous film, and a resin sheet. Even when the structure of each of the above-described examples is replaced with a fiber aggregate, a microporous film, a resin sheet, and the like. The same effect as described above can be obtained.

[0054] The fiber aggregate is configured so that the heat-fusible resin penetrates between a large number of fibers and the fibers. In addition to the nonwoven fabric described above, a woven fabric in which fibers are woven in the course of the process is also used. Including. The opening pressure can also be set arbitrarily in the woven fabric by appropriately setting the basis weight. The microporous film is a film formed by dispersing a large number of micropores. When a microporous film is used as a sheet-like member, the heat-fusible resin permeates into these micropores. As the microporous film, the same material as used for the separator can be used as long as it has a higher melting point than the heat-fusible resin constituting the heat-fused layer of the exterior film. The manufacturing method is also as described in the description of the separator. Use microporous film In this case, the opening pressure can be controlled by appropriately setting the size and distribution density of the micropores. The size and distribution density of the micropores depend on the stretching ratio of the microporous film when manufactured by a dry process, and the diameter of the solvent and fine particles when manufactured by a wet process.

, Depending on the content. The resin sheet, like the microporous film, is formed by dispersing a number of openings through which the molten heat-fusible resin penetrates, and the opening pressure can be controlled by the opening ratio. In the present invention, the resin sheet is distinguished from the microporous film in that the thickness is larger than that of the microporous film. A resin sheet through which molten heat-fusible resin can penetrate can be produced by forming a large number of openings in a raw sheet formed by, for example, a τ die method using a punching method or a heating needle. When a resin sheet is used as the sheet-shaped member, there is an advantage that the size and arrangement of the openings can be freely set and the opening ratio can be arbitrarily controlled.

[0055] The size of the gap between the fibers of the fiber assembly, the pore size of the microporous film, and the pore size of the opening of the resin sheet are as small as possible and the gap between the fibers of the fiber assembly, the pores of the microporous film, It is preferable that the openings of the fat sheet are uniformly arranged over the entire area of these sheet-shaped members. Since these are intended to function as pressure relief parts, it is important to ensure that when internal pressure rises, stable peeling occurs at the part where the path for pressure relief is to be formed. This is because it is preferable that the adhesive strength is uniform.

If the size of the gap between the fibers and the diameter of the pores are too large, inconveniences such as non-uniform bonding strength with the exterior film and a large variation in the opening pressure are caused. For example, if the sealing width (width W2 in Fig. 7) is 10 mm, using a resin sheet with openings of 3 mm in diameter randomly distributed may lead to uneven bonding strength at a pitch of 3 mm. In addition, if two or three openings are arranged in the sealing width direction, the number of openings may differ for each product. In consideration of the above, the size of the gap between the fibers and the pore diameter are preferably 1 mm or less, more preferably 0.5 mm or less, and most preferably 0.1 mm or less. Needless to say, the gap between the fibers and the diameter of the pores need to be large enough to allow the molten heat-fusible resin to penetrate. Regarding the arrangement of the gaps and holes between the fibers, the density should be such that the adhesive strength between the sheet-like member and the exterior film is as uniform as possible. It is preferred to be located! / ,.

Further, in the above-described example, the battery element is sandwiched from both sides in the thickness direction by two exterior films, and the surrounding four sides are heat-sealed. Fold the battery element, open it, and heat seal the three sides to seal the battery element.

[0058] Regarding the structure of the battery element, in the above-described example, a positive electrode, a negative electrode, and a separator were formed in a strip shape in which a plurality of positive electrodes and a plurality of negative electrodes were alternately stacked, and the positive electrode and the separator were sandwiched by a separator. A negative electrode may be a wound-type battery element in which positive electrodes and negative electrodes are alternately arranged by stacking the negative electrode, winding the negative electrode, and compressing the negative electrode.

[0059] As the battery element, any battery element used for a normal battery can be applied as long as it includes a positive electrode, a negative electrode, and an electrolyte. A battery element in a general lithium ion secondary battery includes a positive electrode plate in which a positive electrode active material such as lithium manganese composite oxide and lithium cobalt oxide is coated on both surfaces such as aluminum foil, and a lithium dope. A negative electrode plate coated with a dopable carbon material on both sides such as copper foil is opposed to each other via a separator, and is impregnated with an electrolyte containing a lithium salt. Other battery elements include other types of battery elements such as nickel metal hydride batteries, nickel cadmium batteries, lithium metal primary or secondary batteries, and lithium polymer batteries. Further, the present invention can accumulate electric energy inside and generate gas by a danigami reaction or a physical reaction, such as a capacitor element such as a capacitor such as an electric double layer capacitor or an electrolytic capacitor. The present invention can also be applied to electric devices in which electric device elements are sealed with an exterior film.

Further, FIG. 1 shows an example in which the positive electrode lead 3 and the negative electrode lead 4 are extended from the opposite side of the film-covered battery 1. These forces may extend on the same side. Then, they may extend from adjacent sides.

Example

Next, specific examples of the present invention will be described together with comparative examples.

(Example 1)

Nylon Z aluminum foil Z polypropylene (25 μm thick, Using a laminated film having a laminated structure of 40 ^ m, 50 / zm), battery elements were housed inside to prepare a film-covered battery. The external shape of the film-covered battery was rectangular, and the two opposing short sides pulled out the positive and negative leads, respectively.

[0063] A portion functioning as a safety valve was formed on one of the two long sides of the film-covered battery from which the lead was not drawn out as follows. One nonwoven fabric cut into a rectangle of 20 mm × 20 mm was temporarily fixed to one of the two laminated films on the polypropylene side of the portion to be sealed on the long side. The temporary fixing position of the nonwoven fabric was set at the center of the long side. As the nonwoven fabric, a polyester nonwoven fabric having a basis weight of 18 g / m ² and a thickness of 36 / zm was used. Next, the other laminated film is opposed to the non-woven fabric with the polypropylene layer inside, sandwiching the nonwoven fabric. A sandwiched sealing region was formed. As the heat fusion heater, one having a metal head on one side and a silicone rubber on the other head was used. The heat fusion temperature was 190 ° C. In the heat fusion on the side sandwiching the nonwoven fabric, the heat fusion temperature, pressure, and time were set to the same conditions in each of the following examples and comparative examples including the present example.

(Example 2)

A film-covered battery was produced in the same manner as in Example 1, except that the same nonwoven fabric used in Example 1 was stacked as two nonwoven fabrics to be sandwiched.

(Example 3)

A film-covered battery was produced in the same manner as in Example 1, except that a nonwoven fabric made of polyester having a basis weight of 43 g / m ² and a thickness of 90 m was used as the nonwoven fabric to be sandwiched. The number of sandwiched nonwoven fabrics is one.

(Comparative Example 1)

A film-covered battery was produced in the same manner as in Example 1 except that a non-woven fabric was sandwiched.

[0067] (Evaluation)

The peel strength of the sealed region was measured for the film-covered batteries of Examples 1 to 3 and Comparative Example 1 manufactured as described above. First, in order to obtain a sample for peel strength measurement, a portion where a non-woven fabric is sandwiched (Comparative Example 1 uses a non-woven fabric, so the same as in Examples 1-3) Part) was cut into an elongated shape in the direction from the outside to the inside of the film-covered battery, including the unsealed part. Then, the unsealed portion of the obtained sample was gripped by two chucks of a tensile tester, and the peel strength was measured by a T-type peel test. Table 1 shows the measurement results.

[table 1]

As shown in Table 1, by sandwiching the nonwoven fabric in the sealing region, a portion having a small peel strength was able to be formed. Comparing Example 1 with Example 3, it can be seen that the peel strength can be controlled by the basis weight of the nonwoven fabric to be sandwiched. Further, as shown in Example 2, by laminating a plurality of nonwoven fabrics, the peel strength can be significantly reduced. Specifically, in Example 2, the total basis weight of the two nonwoven fabrics was 36 gZ, and the total thickness was 72 / zm.These values were smaller than those of Example 3, but the peel strength was higher than that of Example 3. It is getting smaller.

Claims

The scope of the claims

[1] electrical device elements,

A heat-sealing layer having a structure in which at least a non-ventilating layer and a heat-sealing resin made of a heat-sealing resin are laminated, the heat-sealing layer surrounding the electric device element with the heat-sealing layer as an inner surface and facing around the electric device element An exterior film in which a sealing region for sealing the electric device element is formed by heat-sealing the two,

At least one sheet of resin arranged at a part of the sealing region and having a melting point higher than that of the heat-fusible resin, and having a structure through which the melted heat-fusible resin can penetrate. And a sheet-like member of

The sheet-shaped member is sandwiched between the facing exterior films and is exposed and arranged in a space surrounding the electric device, and the heat-fusible resin is impregnated in the sheet-shaped member. Film-covered electrical device.

2. The film-covered electric device according to claim 1, wherein the sheet-shaped member is a fiber aggregate made of a resin having a melting point higher than that of the heat-fusible resin.

3. The film-covered electric device according to claim 2, wherein the fiber aggregate is a nonwoven fabric, and the heat-fusible resin penetrates between fibers constituting the nonwoven fabric.

[4] The sheet-like member is a microporous film made of a resin having a melting point higher than that of the heat-fusible resin, and the heat-fusible resin is applied to micropores of the microporous film. The film-covered electrical device according to claim 1, wherein the fat is impregnated.

[5] The film-covered electric device according to claim 1, wherein a plurality of the sheet-shaped members are overlapped and sandwiched by the package film.

[6] A pressure release portion is provided in a region of the exterior film where the sheet-like member is sandwiched, for releasing the exterior film in this region to communicate the inside of the space with outside air. 2. The film-covered electric device according to 1.

7. The film-covered electric device according to claim 6, wherein the pressure release portion is a hole or a cut formed in at least one of the outer films facing each other in the sealing region.

[8] The sealing region has a protrusion projecting toward the electric device element, 7. The film-covered electric device according to claim 6, wherein the nonwoven fabric is sandwiched between portions.

[9] In a part of the sealing region, a non-fused portion in which the exterior films are not thermally fused to each other is continuously formed in a space surrounding the battery element in a cove shape. 9. The film-covered electric device according to claim 8, wherein the projecting portion is provided on the device.

10. The film-covered electric device according to claim 1, wherein the sheet-shaped member has a shape whose size decreases outward from an edge on the battery element side.

11. The film-covered electric device according to claim 1, wherein the heat-sealing resin is polypropylene, and the resin constituting the sheet-like member is polyethylene.

[12] The film-covered electric device according to claim 1, wherein the electric device element is a chemical battery element or a capacitor element.