JP4876915B2 - Film exterior electrical device - Google Patents

Description

  The present invention relates to a film-covered electric device in which electric device elements such as chemical battery elements and capacitor elements represented by batteries and capacitors are sealed with a covering material made of a film.

  Conventionally, as a film-clad battery using a film as a packaging material, a battery element is surrounded by a laminate film in which a metal layer and a heat-sealing resin layer are laminated, and positive and negative leads connected to the battery element are laminated film. A battery element is hermetically sealed (hereinafter also simply referred to as “sealing”) by heat-sealing the open edge of the laminate film in a state where the laminate film is pulled out from the battery.

  As with other types of exterior materials, the battery with a film exterior material is sealed at the heat-sealed part so that the outside air does not enter the battery and the electrolyte in the battery does not leak. It is required to ensure stop reliability. In particular, sealing reliability is important in a battery containing a non-aqueous electrolyte (hereinafter also referred to as “non-aqueous electrolyte battery”). When there is a poor heat fusion, the electrolyte solution deteriorates due to the components of the outside air, and the battery performance is significantly reduced.

  By the way, when a voltage outside the standard range is applied to the battery during use of the battery, gas species may be generated due to electrolysis of the electrolyte solvent. Furthermore, even if the battery is used at a high temperature outside the standard range, a substance that is a source of gas species is generated due to decomposition of the electrolyte salt or the like. Basically, it is ideal to use a battery within the standard range so as not to generate gas. However, if the battery control circuit fails for some reason and an abnormal voltage is applied, or if the surroundings become abnormally hot for some reason, a large amount of gas may be generated in some cases.

  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 extreme rise in internal pressure, many batteries using metal cans as exterior materials have a pressure relief valve that allows gas to escape outside the battery when the internal pressure of the battery rises. ing. However, it is structurally difficult to provide a pressure safety valve in a film-clad battery using a film as a packaging material. In a film-clad battery, if the internal pressure rises too much, the film expands and eventually ruptures and gas is ejected from that location, but it cannot be specified where the rupture occurs. Therefore, depending on the ruptured location, it may adversely affect surrounding equipment and members.

  In view of this, in the conventional film-clad battery, several pressure release structures have been proposed in order to eliminate such problems caused by the generation of gas inside the battery.

  Japanese Unexamined Patent Publication 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 the exterior film. The multilayer sheet is obtained by laminating a resin film having sufficient heat-fusibility with an exterior film on both surfaces of a resin film having a lower melting point than the heat-fusible resin layer of the exterior film. When the temperature is abnormally high, the inner layer of the multilayer sheet is softened and melted, thereby releasing the gas generated inside the battery. In Japanese Patent No. 2725881 (Patent Document 2), a sheet-like member having a melting point higher than that of the heat-fusible resin layer of the exterior film is sandwiched in a part of the sealing portion of the exterior film. A film-clad battery in which an exterior film is in an unfused state in a region where members are interposed is disclosed. Japanese Patent Application Laid-Open No. 11-86823 (Patent Document 3) discloses a film-covered battery in which a sealing means having a low pressure resistance is provided in at least a part of the sealing portion of the exterior film. As a sealing means, it is formed by making the sealing part heat-sealed under a heat-sealing condition such that the peel strength becomes a predetermined value, or by making the material of the fusing material or adhesive different from other parts. The sealing part etc. which were done are illustrated.

  However, since the pressure release structure disclosed in Patent Document 1 is a structure that releases the pressure inside the battery by softening and melting the inner layer of the multilayer sheet, the release pressure depends on the temperature and the melting point of the resin film constituting the inner layer. It is difficult to adjust the opening pressure arbitrarily. Further, in the pressure release structure disclosed in Patent Document 2, since the member sandwiched between the sealing portions is a sheet, the exterior material is not joined in the region where the member is sandwiched, and the sealing reliability is extremely high. It will be lower. Furthermore, in the pressure release structure disclosed in Patent Document 3, as described above, the heat fusion conditions are changed, or the material of the fusion material or the adhesive is different from that of the other parts. However, when the heat fusion conditions are changed, it is difficult to arbitrarily adjust the release pressure because the fusion strength of the exterior material does not change much even if the heat fusion conditions are changed. On the other hand, even if the material of the fusing material or the adhesive is different from the other parts, the release pressure depends on the material of the fusing material or the adhesive. Have difficulty.

  The above is not only a battery but a problem common to film-covered electric devices in which an electric device element that may generate gas is sealed with an outer film.

  An object of the present invention is to provide a film-clad electrical device that can easily set an opening pressure when the film expands due to the generation of gas at the time of abnormality without reducing the sealing reliability of the electrical device element.

  In order to achieve the above object, a film-clad electrical device of the present invention includes an electrical device element and a packaging film having a structure in which at least a non-breathing layer and a thermal fusion layer made of a thermal fusion resin are laminated. The exterior film has a sealing region for sealing the electrical device element by surrounding the electrical device element with the thermal fusion layer as an inner surface and heat-sealing the thermal fusion layers facing each other around the electrical device element. Yes. In a part of the sealing region, at least one sheet-like member made of a resin having a melting point higher than that of the heat-fusible resin is sandwiched between opposing exterior films and exposed in a space surrounding the electric device. Are arranged. The sheet-like member has a structure that allows the melted heat-fusible resin to permeate, and the sheet-like member permeates the heat-fusible resin.

  In the film-covered electrical device of the present invention configured as described above, at least one sheet-like member is sandwiched between facing exterior films in a part of the sealing region. The sheet-like member has a structure that allows the molten heat-fusible resin to penetrate. However, the resin constituting the sheet-like member has a higher melting point than the heat-fusible resin constituting the heat-sealing layer of the exterior film, and is not melted by the heat-sealing for forming the sealing region. Therefore, the peel strength of the portion where the sheet-like member in the sealing region is sandwiched is smaller than that of other portions, and this portion can be preferentially peeled when the internal pressure is increased, and the pressure can be released. By heat-sealing the exterior film, the heat-fusible resin can be infiltrated into the sheet member, and the sealing reliability does not decrease even when the sheet member is interposed. The peel strength at the portion where the sheet-like member is sandwiched depends on the degree of penetration of the heat-fusible resin in the sheet-like member, so that the sheet can be selected by appropriately selecting the degree of penetration of the heat-fusible resin. It is possible to arbitrarily set the peel strength, that is, the open pressure at the portion where the shaped member is sandwiched.

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

  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.

  Furthermore, by providing a pressure release portion that communicates the inside of the space surrounding the electric device element with the outside air by peeling the exterior film in this region in the region where the sheet-like member is sandwiched, the progress of the peeling is caused by this pressure. When the opening is reached, the pressure is released. Therefore, the degree of freedom in setting the release pressure is further increased by appropriately setting the position of the pressure release portion. As a pressure release part, it can be set as the hole or notch | incision formed in at least one of the exterior films which are facing in the sealing area | region, for example.

  According to the present invention, a sheet-like member having a structure in which a melted heat-fusible resin can permeate is sandwiched between exterior films facing each other in a part of the sealing region, and the electrical device element The open pressure can be easily and reliably set without reducing the sealing reliability.

It is a disassembled perspective view of the film-clad battery by one Embodiment of this invention. It is typical sectional drawing along the longitudinal direction of the sealing area | region in the part by which the nonwoven fabric was inserted | pinched of the film-clad battery shown in FIG. It is a figure which shows an example of the arrangement direction of the fiber of the nonwoven fabric pinched | interposed into a sealing area | region. It is a figure which shows the other example of the arrangement direction of the fiber of the nonwoven fabric pinched | interposed into a sealing area | region. It is typical sectional drawing along the longitudinal direction of the sealing area in the portion where the nonwoven fabric was inserted when two nonwoven fabrics were inserted. It is a top view of the sealing area | region in the part in which the nonwoven fabric was pinched | interposed, which shows the other example of the nonwoven fabric pinched | interposed. It is a top view of the sealing area | region in the part in which the nonwoven fabric was inserted of the example which added the through-hole to the part which inserted the nonwoven fabric. It is a top view of the sealing area | region in the part by which the nonwoven fabric was inserted | pinched which shows the modification of the example shown in FIG. It is a top view of the sealing area | region in the part by which the nonwoven fabric was inserted | pinched of the film-clad battery by other embodiment of this invention. It is a perspective view explaining the peeling stress which acts when the boundary of the heat fusion part of an exterior film is a shape without an unevenness | corrugation. It is a perspective view explaining the peeling stress which acts on the protrusion part shown in FIG. It is a top view which shows progress of peeling in the protrusion part shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Film exterior battery 2 Battery element 3 Positive electrode lead 4 Negative electrode lead 5 Exterior film 5a Sealing area 5b Cup part 6 Thermal fusion layer 7 Non-air-permeable layer 8 Non-woven fabric 9 Fiber 10 Through-hole 11 Non-fusion part 12 Protrusion part

  Referring to FIG. 1, a flat, substantially rectangular parallelepiped battery element 2 having a structure in which a plurality of positive electrodes and a plurality of negative electrodes are laminated, and a positive electrode lead 3 and a negative electrode lead 4 respectively connected to the positive electrode and the negative electrode of the battery element 2. A film-clad battery 1 according to an embodiment of the present invention is shown having an exterior film 5 that seals the battery element 2 by extending a part of the positive electrode lead 3 and the negative electrode lead 4.

  In the battery element 2, a plurality of positive electrodes and a plurality of negative electrodes each made of a metal foil coated with an electrode material on both sides are alternately stacked via separators. Each positive electrode and each negative electrode have an uncoated portion where no electrode material is applied. The non-coated portion is provided so as to protrude from one side of each positive electrode and each negative electrode. The uncoated portions of the positive electrodes and the uncoated portions of the negative electrodes 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 opposite sides of the film-covered battery 1. In this embodiment, the planar shape of the film-clad battery 1 is substantially rectangular, and the positive electrode lead 3 and the negative electrode lead 4 are drawn out from the short side of the rectangle.

  In the case of a non-aqueous electrolyte battery such as a lithium ion battery, an aluminum foil is used for the metal foil constituting the positive electrode, and a copper foil is used for the metal foil constituting the 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, the surface may be plated with nickel.

  As the separator, a sheet-like member that can be impregnated with an electrolytic solution, such as a microporous film (microporous film), a nonwoven fabric, or a woven fabric made of a thermoplastic resin such as polyolefin can be used. A microporous film is a dry process in which fine pores are formed in a film by uniaxially or biaxially stretching the film, or a film is formed by melting and kneading a base polymer together with a solvent and fine particles, and then immersed in a solvent or 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 further stretched to be porous as necessary.

  The exterior film 5 is composed of two laminated films that surround and surround the battery element 2 from both sides in the thickness direction, and the battery elements 2 are sealed by heat-sealing the opposing surfaces that overlap each other around the battery element 2. It has been stopped. In FIG. 1, the area | region where the exterior film 5 is heat-sealed is shown by the oblique line as the sealing area 5a. The exterior film 5 has a cup portion 5 b in the center region in order to form a battery element storage portion that is a space surrounding the battery element 2. The sealing region 5a is formed over the entire circumference of the cup portion 5b. The cup portion 5b can be processed by deep drawing. In the example shown in FIG. 1, the cup portion 5b is formed on both the exterior films 5, but the cup portion may be formed on only one of them, or the exterior film 5 may be formed without forming the cup portion. The battery element 2 may be surrounded by using the flexibility.

  As a laminate film constituting the exterior film 5, if it has flexibility and can seal the battery element 2 by heat fusion so that the electrolyte does not leak, this type of film exterior battery can be used. Commonly used films can be used. A typical layer structure of the laminate film used for the exterior film 5 is a structure in which a non-air-permeable layer made of a metal thin film and a heat-bonded layer made of a heat-fusible resin are laminated, or the heat of the non-air-permeable layer. The structure which laminated | stacked the protective layer which consists of films, such as polyester, such as polyethylene terephthalate, and nylon, on the surface on the opposite side to a melt | fusion layer is mentioned. When sealing the battery element 2, the battery element 2 is surrounded with the heat-sealing layer facing each other.

  As the metal thin film constituting the non-breathing layer, for example, a foil made of Al, Ti, Ti alloy, Fe, stainless steel, Mg alloy or the like having a thickness of 10 μm to 100 μm can be used. The heat-sealable resin used for the heat-sealable layer is not particularly limited as long as it is a resin that can be heat-sealable. For example, polyesters such as polypropylene, polyethylene, acid modified products thereof, polyphenylene sulfide, and polyethylene terephthalate. Etc., polyamide, ethylene-vinyl acetate copolymer and the like can be used. The thickness of the heat fusion layer is preferably 10 μm to 200 μm, more preferably 30 μm to 100 μm.

  Non-woven fabric 8 that is sandwiched between exterior films 5 that sandwich battery element 2 and that is exposed and disposed in the battery element storage portion is held in a part of sealing region 5a by thermal fusion between exterior films 5 Has been. The non-woven fabric 8 is made of a resin different from the heat-fusible resin of the outer film 5 having a melting point higher than that of the heat-fusible resin constituting the heat-fusible layer of the outer film 5. . For example, when the heat-fusible resin constituting the heat-sealing layer of the exterior film 5 is polypropylene, the nonwoven fabric 8 can be made of polyethylene terephthalate.

  The heat fusion between 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. As a result, the heat-sealable layer 6 melts but the fibers 9 of the nonwoven fabric 8 do not melt, so that the heat-sealable resin of the heat-sealable layer 6 penetrates between the fibers 9 of the nonwoven fabric 8 as shown in FIG. The nonwoven fabric 8 is embedded and held in the heat-sealing layer 6 of the exterior film 5. In addition, FIG. 2 has shown typically the cross section which cut | disconnected the edge | side where the nonwoven fabric 8 of the sealing area | region 5a was inserted | pinched 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 exterior films 5 are integrated by heat sealing. In FIG. 2, the layer outside the heat-sealing layer 6 is a non-breathing layer 7 of the exterior film 5.

  A structure in which the nonwoven fabric 8 is sandwiched between the exterior films 5 facing each other in the sealing region 5a can be produced, for example, as follows. First, the non-woven fabric 8 cut in advance to a predetermined size is placed on a portion that becomes one of the sealing regions 5a 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 or the like. The temporary fixing does not require the nonwoven fabric 8 to be firmly fixed to the exterior film 5 and may be enough to hold the nonwoven fabric 8 on the exterior film 5 until the sealing region 5a is finally formed. Next, the battery element 2 to which the positive electrode lead 3 and the negative electrode lead 4 are connected is placed on the exterior film 5 to which the nonwoven fabric 8 is temporarily fixed, and another sheet of the exterior film 5 is placed thereon to surround the battery element 2. The outer film 5 is heat-sealed over the entire circumference. The heat fusion temperature at this time is higher than the melting point of the heat-fusible resin constituting the heat-fusion layer 6 of the exterior film 5 and lower than the melting point of the resin constituting the nonwoven fabric 8 as described above. And Thereby, the heat-sealed part of the exterior film 5 becomes the sealing region 5a, and the film-covered battery 1 in which the nonwoven fabric 8 is interposed in a part thereof is obtained.

  In the film-clad battery 1 configured as described above, when a voltage outside the standard range is applied during use or gas is generated from the battery element 2 due to a temporary high temperature, the film-clad battery 1 The internal pressure increases. When the internal pressure rises, the battery element storage portion, which is a space surrounded by the cup portion 5b of the exterior film 5, tends to swell in a dome shape, and peeling stress acts on the inner edge of the sealing region 5a.

  A non-woven fabric 8 is sandwiched in a part of the sealing region 5a, and in the portion where the non-woven fabric 8 is sandwiched, as shown in FIG. 8 fibers 9 are soaked. For this reason, the heat-sealable layer 6 has a heat-sealable resin continuously above and below the non-woven fabric 8 while the non-woven fabric 8 is interposed therebetween. The adhesive resin is not divided in the thickness direction of the heat sealing layer 6. Therefore, the sealing performance required for the sealing region 5a can be obtained.

  Furthermore, by sandwiching the nonwoven fabric 8, in the region where the nonwoven fabric 8 is sandwiched, the adhesion region between the heat-sealing layers 6 of the respective exterior films 5, that is, the area where the heat-sealing resin is continuously connected is the same area. It becomes smaller than other regions where the non-woven fabric 8 is not sandwiched. Since the non-woven fabric 8 is made of a resin having a higher melting point, which is different from the heat-sealable resin constituting the heat-sealable layer 6, the adhesive strength between the resin constituting the non-woven fabric 6 and the heat-sealable resin. Is smaller than the adhesive strength between the heat-fusible resins.

  As a result, the portion where the nonwoven fabric 8 is sandwiched can be peeled off with a small peeling stress as compared with the other sealing regions 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 at the portion where the nonwoven fabric 8 is sandwiched. When peeling of the exterior film 5 proceeds and reaches the outer edge of the sealing region 5a, the battery element storage portion communicates with the outside (outside air) of the film exterior battery 1, and thereby the increased pressure is released. Therefore, gas can be ejected from a specific position before the film-clad battery 1 is ruptured, and rupture of the film-clad battery 1 and gas ejection in an unintended direction can be prevented.

  The peel strength of the sealing region 5a depends on the presence ratio of the heat-fusible resin in the heat-fusible layer 6. If this abundance ratio is high, the peel strength tends to be high, and if the abundance ratio is low, the peel strength tends to be low. On the other hand, the proportion of the heat-fusible resin in the heat-sealing layer 6 depends on the basis weight of the nonwoven fabric 8 to be sandwiched. If the basis weight is large, the presence ratio of the heat-sealable resin is low, and if the basis weight is small, the presence ratio of the heat-sealable resin tends to be high. From the above, by appropriately setting the basis weight of the nonwoven fabric 8 to be sandwiched, the peel strength in the region where the nonwoven fabric 8 is sandwiched can be adjusted. The fact that the peel strength is small means that the gas can be released with such a low internal pressure. Thus, by setting it as the structure which sandwiches the nonwoven fabric 8 and adjusts peeling strength, the fabric weight of the nonwoven fabric 8 can be set suitably and the open pressure of gas can be set arbitrarily.

  Further, by using a nonwoven fabric 8 that is an aggregate of fibers 9 as a member to be sandwiched in a portion where gas is to be released, different types of resins as seen in a conventional resin sandwiched safety valve structure can be obtained at a planar interface. Unlike the case where it is apparently bonded, it is possible to achieve both long-term reliability of adhesion to an electrolytic solution, which is an organic solvent, and ease of operation that can be operated with a small force at the time of abnormality.

  As the sandwiched nonwoven fabric 8, any of wet type, dry type (resin bonding, thermal bond, spun lace) and spun bond type (melt spinning, wet spinning, flash spinning, melt blow) may be used. Further, in the nonwoven fabric 8, there are fibers in which the fibers 9 are arranged in almost one direction and those in which the fibers 9 are randomly arranged. For adjusting the peel strength, the ratio of the fibers 9 in the heat-sealing layer 6 is determined. 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 substantially parallel to the direction from the outer edge to the inner edge of the sealing region 5a. 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 region 5a. Of course, the arrangement direction of the fibers 9 may be different from these directions. Here, the inner edge of the sealing region 5 a is an edge on the battery element 2 side, and the outer edge is an edge on the side away from the battery element 2.

  As described above, in order to lower the release pressure, the basis weight of the sandwiched nonwoven fabric 8 may be increased. However, there is a limit to reducing the opening pressure with only the single nonwoven fabric 8. In addition, since the thickness of the nonwoven fabric 8 generally increases with the size of the basis weight, if the thickness of the nonwoven fabric 8 is too thick in order to obtain a desired basis weight, The fusible resin does not sufficiently permeate between the fibers 9 of the nonwoven fabric 8 and the sealing reliability may be impaired. Therefore, when a lower release pressure is required, it is preferable to sandwich the two nonwoven fabrics 8 as shown in FIG.

  By stacking the two nonwoven fabrics 8, the peel strength can be reduced more than when one nonwoven fabric 8 having the same basis weight as the total basis weight of the two nonwoven fabrics 8 is sandwiched. This is because, by overlapping two nonwoven fabrics 8, the region where the heat-fusible resin permeating each nonwoven fabric 8 is reduced at the boundary between the two nonwoven fabrics 8, compared to the case of one nonwoven fabric 8. This is thought to be because the adhesion region between the heat-fusible resins becomes smaller. The number of non-woven fabrics 8 to be overlapped is not limited to two, and may be three or more when it is necessary to set a lower opening pressure.

  The shape and size of the non-woven fabric 8 are not particularly limited as long as the non-woven fabric 8 has a shape or size having a portion that extends from the outer edge to the inner edge of the sealing region 5a. Although the rectangular nonwoven fabric 8 is shown in FIG. 1, the length L1 of the inner edge of the nonwoven fabric 8 is longer than the length L2 of the outer edge, such as the trapezoidal shape shown in FIG. It can also be set as the nonwoven fabric 8 of the shape where a dimension becomes small toward it. Thereby, since the shape of the nonwoven fabric 8 becomes a shape according to progress of peeling, peeling can be advanced smoothly. Here, similarly to the inner edge and the outer edge of the sealing region 5a described above, the inner edge and the outer edge of the non-woven fabric 8 are the inner edge on the battery element 2 side and the outer edge on the side away from the battery element 2, respectively. Also in this case, the number of the nonwoven fabrics 8 to be sandwiched can be used by overlapping a plurality of sheets as well as one.

  Furthermore, as shown in FIG. 6, the through-hole 10 which penetrates the exterior film 5 can also be formed as a pressure release part in the area | region where the nonwoven fabric 8 of the sealing area | region 5a was pinched | interposed. By forming the through hole 10, the inside of the battery element storage portion communicates with the outside air when the progress of the peeling reaches the through hole 10, and the pressure can be released. The opening pressure can be adjusted also 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 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 to the outside of the through hole 10. Therefore, when the through-hole 10 which is a pressure release part 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 5a, the substantial opening pressure does not change. Moreover, by this, the size of the nonwoven fabric 8 can be made small and the usage-amount of the nonwoven fabric 8 can be decreased. The widths of the nonwoven fabric 8 and the sealing region 5a mean the length in the direction from the outer edge to the inner edge of the sealing region 5a. 6 and FIG. 7, the shape of the nonwoven fabric 8 is arbitrary. For example, the shape shown in FIG. 5 can be used, and the number of nonwoven fabrics 8 to be sandwiched is not only one but also a plurality of sheets. Can be used in layers.

  6 and 7 show examples in which the through hole 10 is provided as the pressure release portion, 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 region of the nonwoven fabric 8 from the outer edge to the inner edge of the sealing region 5a in the middle of the nonwoven fabric 8. In this case, the release pressure can be arbitrarily adjusted depending on the position of the tip of the cut. Further, the pressure release portion does not need to have a structure that penetrates two overlapping exterior films, and the same effect can be obtained even when a through hole or a cut is formed in only one of the two overlapping exterior films. Is obtained.

  In the embodiment described above, an example in which the sealing region 5a is formed with a constant width has been shown. However, the shape of the sealing region 5a itself is a shape in which the peeling stress is likely to act locally, and the effect of the nonwoven fabric 8 is achieved. Can also be exhibited more effectively. An example is shown in FIG.

  In the example shown in FIG. 8, two non-fused portions 11, which are portions where the exterior films facing each other are not thermally fused, are formed on the edge of the sealing region 5 a on the battery element 2 side. It is continuously formed into a cove shape. The two non-fused portions 11 are spaced apart from each other in the direction along the periphery of the sealing region 5a, whereby the region between the non-fused portions 11 faces the battery element storage portion. It is the protrusion part 12 which protruded. The nonwoven fabric 8 is located in the protruding portion 12, and the exterior film facing the nonwoven fabric 8 through the nonwoven fabric 8 is heat-sealed. Furthermore, a through hole 10 that is a pressure release portion is formed in the protruding portion 12.

  Thus, by providing the projecting portion 12 projecting toward the battery element storage portion in the sealing region 5a, when the internal pressure of the film-clad battery increases due to the generation of gas from the battery element 2, the sealing region 5a In this case, the peeling stress of the exterior film acts intensively on the protruding portion 12, and the peeling of the exterior film proceeds preferentially at the protruding portion 12. As the internal pressure increases, the separation reaches the position of the through hole 8, so that the battery element housing portion communicates with the outside of the film-clad battery, and the increased pressure is released through the through hole 8.

  Below, the progress of peeling of the exterior film accompanying an increase in internal pressure will be described in detail.

  When the boundary between the heat-sealed area and the non-heat-bonded area of the exterior film has an uneven shape, the peeling stress F1 acts only in one direction as shown in FIG. 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 filled with gas and protrudes as shown in FIG. Since the exterior film 5 swells also on both sides of the portion 12, the peeling stress F2 acts on the protruding portion 12 in addition to the peeling stress F1 acting on the tip thereof. Therefore, a peeling stress larger than that of other parts acts as a resultant force on the corners of the projecting portion 12, and the outer film 5 is peeled off in preference to other parts at the corners. When the exterior film 5 is peeled off at the corners, the corners are rounded, but the protrusions 12 still maintain the convex shape, and the protrusions 12 are peeled off from a plurality of directions. Therefore, the peeling of the exterior film 5 preferentially peels off the exterior film 5 at the projecting portion 12 until the projecting portion 12 is almost eliminated while reducing the sharpness of the convex shape. proceed.

  FIG. 11 shows the progress of peeling of the exterior film 5 at the protruding portion 12. As shown in FIG. 11, in the projecting portion 12, peeling progresses from both sides of the projecting 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 protrusion 12, the protrusion length L of the protrusion 12, and the internal pressure. Therefore, if the material of the exterior film 5, the width Wp of the protruding portion 12, and the protruding length L of the protruding portion 12 are determined in advance, the inside and outside of the battery element storage portion can be adjusted by adjusting the position of the through hole 8. An open pressure, which is an internal pressure of the battery element storage portion when and communicate with each other, can be arbitrarily set. That is, if the through hole 8 is provided at a position close to the tip of the protruding portion 12, the pressure can be released with a low internal pressure, and if the through hole 8 is provided near the base of the protruding portion 12, the pressure is released to a high internal pressure. do not do.

  As described above, by providing the protruding portion 12 in the sealing region 5a, 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 in the protruding portion 12, this function by the protruding portion 12 and the above-described operation effect by the nonwoven fabric 8 are combined, and the release pressure can be controlled more reliably and easily.

  The stress concentration portion provided in the sealing region 5a is not limited to the shape shown in FIG. 8 as long as the peeling stress can be concentrated and act. For example, if the shape of the protrusion 12 in FIG. 8 substantially protrudes toward the battery element 2, the stress concentration portion can be any shape such as a tapered shape or an arc-shaped tip. As a function. 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 the non-fused portion 11 being provided. Good. In any case, the nonwoven fabric 8 is sandwiched between the facing exterior films at the stress concentration portion, and a pressure release portion is provided at this portion.

  In order to effectively promote the peeling 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 portion is most likely to act. For this purpose, as shown in FIG. 1, of the sides around the film-clad battery 1, the long side from which the positive electrode lead 3 and the negative electrode lead 4 are not drawn out is substantially the center in the direction along the side. The nonwoven fabric 8 is preferably sandwiched between the two.

  The present invention has been described above with some typical examples. However, the present invention is not limited to these examples, and it is obvious that the present invention can be appropriately modified within the scope of the technical idea of the present invention. .

  For example, although the example which used the nonwoven fabric as the sheet-like member arrange | positioned between the exterior films which oppose in a sealing area | region was shown in the example mentioned above, the sheet-like member in this invention comprises the heat-fusion layer of an exterior film. The nonwoven fabric is not limited as long as it is made of a resin having a melting point higher than that of the heat-fusible resin and has a structure that allows the molten heat-fusible resin to penetrate. Examples of such a sheet-like member include a fiber assembly, a microporous film, a resin sheet, etc. Even if the structure of each example described above is replaced with a fiber assembly, a microporous film, a resin sheet, etc. The same effect can be obtained.

  The fiber assembly is composed of a large number of fibers so that the heat-fusible resin penetrates between the fibers, and includes a woven fabric in which the fibers are woven in addition to the above-described nonwoven fabric. Also in the woven fabric, the release pressure can be arbitrarily set 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 penetrates 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-melting layer of the exterior film. Is as described in the description of the separator. When a microporous film is used, 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 stretch ratio of the film when the microporous film is produced by a dry process, and depend on the diameter and content of the solvent and fine particles when produced by a wet process. Similarly to the microporous film, the resin sheet is formed by dispersing a large 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. The resin sheet into which the melted heat-fusible resin can permeate can be produced by forming a large number of openings by punching, hot needles, or the like on a sheet original formed by, for example, a T-die method. When a resin sheet is used as the sheet-like member, there is an advantage that the aperture ratio can be arbitrarily controlled by freely setting the size and arrangement of the aperture.

  The size of the gap between the fibers of the fiber assembly, the pore diameter of the microporous film, and the pore diameter of the opening of the resin sheet are as small as possible, and the gap between the fibers of the fiber assembly, the hole of the microporous film, and the opening of the resin sheet are It is preferable that the sheet-like members are uniformly arranged over the entire area. Since these are intended to function as a pressure release portion, it is important that when the internal pressure rises, it is important to stably peel off at the path formation planned portion for pressure release. This is because the adhesive strength is preferably uniform.

  If the size of the gap between the fibers and the hole diameter are too large, there will be inconveniences such as non-uniform adhesive strength with the exterior film and increased individual variations in the opening pressure. For example, when the sealing width (width W2 in FIG. 7) is 10 mm, if a resin sheet in which openings with a diameter of 3 mm are randomly distributed is used, non-uniform adhesion strength is caused at a pitch of 3 mm. Moreover, it is conceivable that the number of openings varies from product to product, such as two or three openings arranged in the sealing width direction. Considering the above, the size of the gap between the fibers and the hole diameter are preferably 1 mm or less, more preferably 0.5 mm or less, and most preferably 0.1 mm or less. Of course, the gaps and pore sizes between fibers need to be large enough to allow the melted heat-fusible resin to penetrate. Regarding the arrangement of the gaps and holes between the fibers, it is preferable that they are arranged at such a density that the adhesive strength between the sheet-like member and the exterior film is as uniform as possible.

  In the above-described example, the battery element is sandwiched from two sides in the thickness direction with two outer films, and the four surrounding sides are heat-sealed. In addition, one outer film is folded in two. The battery element may be sealed by sandwiching the battery element and thermally fusing the three open sides.

  Regarding the structure of the battery element, the above example shows a stacked type in which a plurality of positive electrodes and a plurality of negative electrodes are alternately stacked. However, the positive electrode, the negative electrode, and the separator are formed in a strip shape, and the positive electrode and the negative electrode are stacked with the separator interposed therebetween. After winding this, it may be a wound battery element in which the positive electrode and the negative electrode are alternately arranged by compressing in a flat shape.

  As the battery element, any battery element used for a normal battery is applicable as long as it includes a positive electrode, a negative electrode, and an electrolyte. Battery elements in a typical lithium ion secondary battery include a positive electrode plate in which a positive electrode active material such as lithium-manganese composite oxide and lithium cobaltate is applied on both sides of an aluminum foil, etc., and carbon that can be doped / undoped with lithium. A negative electrode plate coated with a material on both sides of a copper foil or the like is opposed to each other with a separator interposed between them and impregnated with an electrolytic solution containing a lithium salt. Other battery elements include battery elements of other types of chemical batteries such as nickel metal hydride batteries, nickel cadmium batteries, lithium metal primary batteries or secondary batteries, lithium polymer batteries, and the like. Furthermore, the present invention provides an external device that can store gas in a chemical reaction or a physical reaction by accumulating electric energy, such as a capacitor element exemplified by a capacitor such as an electric double layer capacitor and an electrolytic capacitor. The present invention can also be applied to an electric device sealed with a film.

  Further, FIG. 1 shows an example in which the positive electrode lead 3 and the negative electrode lead 4 are extended from opposite sides of the film-clad battery 1, but these may be extended from the same side or adjacent to each other. You may extend from the side.

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

Example 1
As the exterior film, a laminate film having a laminated structure of nylon / aluminum foil / polypropylene (thicknesses of 25 μm, 40 μm, and 50 μm, respectively) was used. The outer shape of the film-clad battery was rectangular, and the positive electrode lead and the negative electrode lead were drawn out from two opposing short sides, respectively.

A portion functioning as a safety valve was formed on one of the two long sides from which the lead of the film-clad battery was not drawn out as follows. One non-woven fabric cut into a 20 mm × 20 mm rectangle was temporarily fixed to the polypropylene side of one of the two laminated films on the long side to be sealed. The temporary fixing position of the nonwoven fabric was the central part 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 μm was used. Next, another laminate film was opposed so that the nonwoven fabric was sandwiched with the polypropylene layer inside, and the two laminate films were heat-sealed by a 10 mm wide elongated heat fusion heater, and the nonwoven fabric was sandwiched. A sealing region was formed. As the heat fusion heater, the head on one side was made of metal, and the head on the other side was bonded with silicone rubber on the surface. The heat fusion temperature was 190 ° C. In the heat fusion of the sides sandwiching the nonwoven fabric, the heat fusion temperature, pressure, and time were the same in each of the examples and comparative examples described below including this example.

(Example 2)
A film-clad battery was produced in the same manner as in Example 1 except that two sheets of the same nonwoven fabric used in Example 1 were stacked as the sandwiched nonwoven fabric.

(Example 3)
A film-clad battery was prepared in the same manner as in Example 1 except that a polyester nonwoven fabric having a basis weight of 43 g / m ² and a thickness of 90 μm was used as the sandwiched nonwoven fabric. The number of sandwiched nonwoven fabrics is one.

(Comparative Example 1)
A film-clad battery was produced in the same manner as in Example 1 except that the nonwoven fabric was not sandwiched.

(Evaluation)
About the film-clad battery of Examples 1-3 and the comparative example 1 produced as mentioned above, the peeling strength of the sealing area | region was measured. First, in order to obtain a sample for measuring peel strength, an exterior film including a part sandwiched with a nonwoven fabric (comparative example 1 does not use a nonwoven fabric, and the same part as in Examples 1 to 3) is taken from the outside of the film exterior battery. In the direction toward the inside, it was cut out to include a portion that was not sealed. And about the obtained sample, the part which is not sealed was gripped by two chucks of a tensile tester, and peel strength was measured by a T-type peel test. The measurement results are shown in Table 1.

表１からわかるように、封止領域に不織布を挟み込むことによって、剥離強度の小さい部分を形成することができた。実施例１と実施例３を比較すると、挟み込む不織布の目付量によって、剥離強度の制御が可能であることがわかる。また、実施例２からわかるように、複数枚の不織布を重ねることにより、剥離強度を大幅に小さくすることが可能である。具体的には、実施例２では、２枚の不織布の合計の目付量は３６ｇ／ｍ²、総厚は７２μｍであり、これらの値は実施例３よりも小さいが、実施例３よりも剥離強度が小さくなっている。

As can be seen from Table 1, a portion having a small peel strength could be formed by sandwiching the nonwoven fabric in the sealing region. Comparing Example 1 and Example 3, it can be seen that the peel strength can be controlled by the basis weight of the nonwoven fabric sandwiched. Moreover, as can be seen from Example 2, it is possible to significantly reduce the peel strength by stacking a plurality of nonwoven fabrics. Specifically, in Example 2, the total basis weight of the two nonwoven fabrics is 36 g / m ² , and the total thickness is 72 μm. These values are smaller than those in Example 3, but are peeled off from Example 3. The strength is small.

Claims (12)

An electrical device element;
The heat sealing layers having a structure in which at least a non-air-permeable layer and a heat sealing layer made of a heat sealing resin are laminated, and surrounding the electrical device element with the heat sealing layer as an inner surface and facing each other around the electrical device elements An exterior film in which a sealing region for sealing the electric device element is formed by heat-sealing,
At least one sheet-like member made of a resin having a melting point higher than that of the heat-fusible resin and having a structure in which the molten heat-fusible resin can permeate is disposed in a part of the sealing region And having
The sheet-like member is sandwiched between the facing exterior films and is exposed and arranged in a space surrounding the electrical device, and the sheet-like member is infiltrated with the heat-fusible resin. device.   The film-covered electrical device according to claim 1, wherein the sheet-like member is a fiber assembly made of a resin having a melting point higher than that of the heat-fusible resin.   The film-covered electrical device according to claim 2, wherein the fiber assembly is a nonwoven fabric, and the heat-fusible resin permeates between fibers constituting the nonwoven fabric.   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 penetrates into micropores of the microporous film. 2. The film-clad electrical device according to 1.   The film-covered electrical device according to claim 1, wherein a plurality of the sheet-like members are overlapped and sandwiched between the exterior films.   2. The film according to claim 1, wherein a pressure release portion is provided in a region where the sheet-like member of the exterior film is sandwiched to communicate the inside of the space with outside air by peeling the exterior film in this region. Exterior electrical device.   The film-covered electrical device according to claim 6, wherein the pressure release portion is a hole or a cut formed in at least one of the exterior films facing each other in the sealing region.   The film-sealed electrical device according to claim 6, wherein the sealing region has a protruding portion that protrudes toward the electric device element, and the nonwoven fabric is sandwiched in the protruding portion.   In a part of the sealing region, a non-fused portion in which the exterior films are not heat-sealed is formed continuously in a space surrounding the battery element, and the protrusion protrudes into the ridge-shaped portion. The film-covered electrical device according to claim 8, wherein a portion is provided.   The film-covered electrical device according to claim 1, wherein the sheet-like member has a shape that decreases in size from the edge on the battery element side toward the outside.   The film-covered electrical device according to claim 1, wherein the heat-sealing resin is polypropylene, and the resin constituting the sheet-like member is polyethylene.   The film-covered electrical device according to claim 1, wherein the electrical device element is a chemical battery element or a capacitor element.

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