JP5422842B2 - Electrochemical devices - Google Patents

Description

  The present invention is applied to a lithium ion secondary battery, an electric double layer capacitor, or the like, and particularly relates to an electrochemical device having a large size, a large capacity and a high output density, and related technology.

  For example, as shown in Patent Document 1, a laminated electrochemical device used as a thin battery includes a power generation element including an electrode and an electrolyte accommodated in a packaging outer film, and a lead terminal connected to the power generation element. The peripheral portion of the exterior film is welded (heat sealed) in a state in which the portion is pulled out, thereby providing a structure in which the power generation element is enclosed.

  The laminate material for packaging as an exterior film in such an electrochemical device generally has a three-layer structure, and the outer surface layer disposed on the outside thereof is a material having mechanical strength and electrical insulation, such as polyethylene. It is made of a synthetic resin such as polyester such as terephthalate or polyamide such as nylon. Further, the inner surface layer disposed on the inner side is in contact with a power generation element such as an electrolytic solution, so that the material has both electrical insulation and thermal adhesive properties, such as high density polyethylene, low density polyethylene, linear low density polyethylene, polyethylene. For example, a vinyl acetate copolymer resin, an ionomer, and a polyolefin resin such as polypropylene. Furthermore, the intermediate layer located between the outermost layer and the innermost layer is made of a material that can prevent moisture from entering from the outside and evaporation of the electrolytic solution to the outside, such as an aluminum foil or a metal foil such as a SUS foil. Yes. The outer surface layer protects the metal foil as the intermediate layer, and also serves to protect it from external forces such as piercing.

  In order to produce an electrochemical device having a packaging laminate material having such a configuration, the packaging laminate material is cut into a rectangular shape, for example, as an exterior film, and in such a state that an element containing an electrode, an electrolytic solution, or the like is accommodated. A sealing portion such as a peripheral portion of the exterior film is subjected to thermocompression bonding, whereby an electrochemical element such as the electrode or the electrolytic solution is enclosed in the exterior film.

  By the way, a pair of lead terminals in this electrochemical device are pulled out from the seal portion of the exterior film, and the portion corresponding to the seal portion is welded so that the inner surface layer of the exterior film is thermally weldable (thermoplastic) synthetic resin. However, when sealed, the lead terminal may break through the inner surface layer of the outer film and contact the metal foil of the intermediate layer to cause a short circuit.

  In order to prevent such a problem, for example, as shown in Patent Document 2, a technique for covering a position corresponding to a seal portion of an exterior film in a lead terminal with a sealing film has been proposed. Specifically, a portion corresponding to the seal portion in the positive electrode lead terminal or the negative electrode lead terminal is previously coated with a sealing film of a heat-adhesive synthetic resin having insulating properties.

  However, even if the technology for covering the lead terminal with the sealing film is applied in this way, it is sufficient due to insufficient adhesion between the synthetic resin that is the constituent material of the sealing film and the metal that is the constituent material of the lead terminal. As a result, it was an obstacle to prolonging the cycle life of the battery.

  In order to solve this problem, for example, as shown in Patent Document 3, a technique using a laminated structure as a sealing film to be covered with a lead terminal has been proposed. This sealing film has a heat-adhesive synthetic resin layer with good adhesion to the metal constituting the lead terminal as the innermost layer, an intermediate insulating layer made of an insulating synthetic resin layer on it, and an olefin resin layer as the outermost layer in order. These are laminated, and this sealing film covers the position corresponding to the seal portion of the lead terminal.

Japanese Examined Patent Publication No.59-38708 Japanese Patent Laid-Open No. 10-302756 JP 2001-57184 A

  However, as shown in Patent Document 3 above, in an electrochemical device in which a lead film is coated with a multi-layer sealing film, the sealing film is not securely adhered over the entire circumference of the lead terminal, and both side edges of the REIT terminal In addition, a gap (cavity) may be formed between the sealing film and the sealing film. Due to this gap, there arises a problem that the durability is lowered, for example, the sealing performance is lowered and the battery life is shortened.

  In particular, when the electrochemical device as described above is used as a power battery for large capacity and large current applications, such as an automobile battery for an electric vehicle or a hybrid vehicle, a lead terminal having a large cross-sectional area for large current, that is, Since the lead terminal having a large thickness is used, a gap is easily formed between the side edge portion of the lead terminal and the sealing film, and the above-described problem is remarkably generated.

  The present invention has been made in view of the above problems, and an electrochemical device capable of adhering a sealing film over the entire circumference of a lead terminal without a gap, and capable of improving sealing performance and durability, and its The purpose is to provide related technology.

  In order to achieve the above object, the present invention comprises the following means.

[1] An exterior film made of a thermoadhesive synthetic resin on the inner surface side, an electrochemical element housed in the exterior film, an inner end portion electrically connected to the electrochemical element, and an outer end portion being the exterior package A lead terminal disposed outside the film, and a sealing film that covers a part of the lead terminal, in a state where the lead terminal is sandwiched through the sealing film by a seal portion of the exterior film, An electrochemical device to which a seal portion of the exterior film is welded,
The sealing film is provided between the outermost layer having compatibility with the inner surface side of the exterior film, the innermost layer having adhesiveness with the lead terminal, the outermost layer and the innermost layer, and from the innermost layer. Also has an intermediate insulating layer with a high melting point,
An electrochemical device, wherein the sealing film is adjusted to have a tensile strength of 15 N / mm ² or less when stretched by 5%.

  [2] The electrochemical device according to item 1, wherein the difference between the melting point of the innermost layer and the melting point of the intermediate insulating layer in the sealing film is 5 ° C. or higher.

  [3] The electrochemical device according to item 1 or 2, wherein the intermediate insulating layer is made of polyvinylidene chloride.

  [4] The electrochemical device according to item 1 or 2, wherein the intermediate insulating layer is formed of an acid-modified olefin resin.

[5] The electrochemical device according to item 1 or 2, wherein the intermediate insulating layer is made of an olefin resin modified with maleic acid .

  [6] The electrochemical device according to any one of items 1 to 5, wherein the lead terminal has a thickness of 0.2 to 1.5 mm.

  [7] The electrochemical device according to any one of items 1 to 6, wherein the sealing film has a thickness of 0.08 to 0.25 mm.

  [8] The electrochemical device according to any one of items 1 to 7, wherein the thickness of the intermediate insulating layer is 20 to 60% with respect to the total thickness of the sealing film.

[9] The electrochemical device according to any one of 1 to 8 above,
A thin battery characterized in that the electrochemical element is constituted by a battery power generation element including at least a positive electrode, a negative electrode, and an electrolyte interposed between both positive and negative electrodes.

[10] A step of preparing a bag-shaped exterior film in which the inner surface side is made of a heat-adhesive synthetic resin and the peripheral portion excluding the seal portion is fused;
A step of preparing a lead terminal in which an electrochemical element is electrically connected to one end and a part thereof is covered with a sealing film;
While accommodating the electrochemical element in the exterior film, with the other end portion of the lead terminal arranged outside, while sandwiching the lead terminal through the sealing film by the seal portion of the exterior film, Welding the seal portion of the exterior film,
As the sealing film, the outermost layer having compatibility with the inner surface side of the exterior film, the innermost layer having adhesion with the lead terminal, the outermost layer and the innermost layer, and the innermost layer from the innermost layer And an intermediate insulating layer having a high melting point, wherein the tensile strength when stretched by 5% is adjusted to 15 N / mm ² or less.

[11] An exterior film made of a thermoadhesive synthetic resin on the inner surface side, an electrochemical element housed in the exterior film, an inner end portion electrically connected to the electrochemical element, and an outer end portion being the exterior package In an electrochemical device comprising: a lead terminal disposed outside the film; wherein the lead terminal is sandwiched by the seal portion of the outer film, and the outer film and the lead are welded to the seal portion of the outer film A sealing film covering a part of the lead terminal so as to be interposed between the terminals,
An outermost layer having compatibility with the inner surface side of the outer film, an innermost layer having adhesiveness with the lead terminal, an intermediate insulation provided between the outermost layer and the innermost layer and having a higher melting point than the innermost layer And having a layer
A sealing film in an electrochemical device, wherein the tensile strength when stretched by 5% is adjusted to 15 N / mm ² or less.

  In the present invention, the term “welding” refers to bonding a thermoplastic (thermoadhesive) material by melting it with heat and applying pressure and cooling, and is used in the same meaning as heat sealing, fusing, and thermal bonding. ing.

  According to the electrochemical device of the invention described in [1], since the sealing film has sufficient flexibility, the sealing film can be closely adhered over the entire circumference of the lead terminal, and the seal And durability can be improved.

  According to the electrochemical device of the invention described in item [2], it is possible to prevent a short circuit between the metal foil that is the intermediate layer of the exterior film and the lead terminal.

  According to the electrochemical device of the inventions described in [3] to [5] above, the sealing film can be more reliably adhered to the lead terminal.

  According to the electrochemical device of the invention described in [6] above, it can be suitably used for a battery for high current use such as power.

  According to the electrochemical device of the inventions described in [7] and [8] above, the sealing film can be more closely adhered to the lead terminal.

  According to the thin battery of the invention described in [9], the same operational effects can be obtained as described above.

  According to the method for producing an electrochemical device of the invention described in [10], an electrochemical device having the same effects as described above can be reliably produced.

  According to the sealing film in the electrochemical device of the invention described in the previous item [11], the same operational effects are obtained as described above.

FIG. 1 is a cross-sectional view showing a thin battery to which an electrochemical device according to an embodiment of the present invention is applied. FIG. 2 is an exploded perspective view showing the thin battery according to the embodiment in an exploded manner. FIG. 3 is an exploded cross-sectional view showing the thin battery according to the embodiment in an exploded manner. FIG. 4 is an enlarged cross-sectional view illustrating a part of the exterior film in the thin battery according to the embodiment. FIG. 5 is a perspective view showing the vicinity of the seal portion in the lead terminal of the thin battery according to the embodiment. FIG. 6 is a cross-sectional view showing the vicinity of the seal portion of the lead terminal of the thin battery according to the embodiment. FIG. 7 is a perspective view showing a state in which an electrochemical element is accommodated in an exterior film processed into a bag shape. FIG. 8 is an enlarged cross-sectional view showing a part of the sealing film in the thin battery according to the embodiment. FIG. 9 is a cross-sectional view showing the periphery of a seal portion in an electrochemical device sample according to an embodiment related to the present invention. FIG. 10 is a cross-sectional view showing the periphery of a seal portion in an electrochemical device sample of a comparative example that departs from the gist of the present invention.

  1 is a sectional view showing a thin battery to which an electrochemical device according to an embodiment of the present invention is applied, FIG. 2 is an exploded perspective view, and FIG. 3 is an exploded sectional view.

  As shown in these drawings, the thin battery of the present embodiment includes two exterior films (4) and (4) whose peripheral portions are welded and the inside is sealed, and exterior films (4) and (4). The electrochemical element (10) to be accommodated and the inner end (5a) (6a) as one end are connected to the electrochemical element (10), and the outer end (5b) (6b) as the other end. A pair of lead terminals (5) and (6) disposed outside the exterior films (4) and (4), and lead-out portions (seal portions 4d) of the exterior films (4) and (4) in the lead terminals (5) and (6) ) And sealing films (7) and (7) that are covered at positions.

  The electrochemical element (10) is configured by laminating a positive electrode (1) and a negative electrode (2) via an electrolyte part (3). The electrolyte part (3) is composed of, for example, a combination of a separator and an electrolytic solution, a combination of a separator and a gel electrolyte, a combination of a gel electrolyte, a combination of a solid electrolyte, and the like. Needless to say, the electrolyte part (3) is not limited to the exemplified configuration.

Further, the positive electrode (1) and the negative electrode (2) are made of a metal foil, for example, an aluminum foil or a copper foil, and a positive electrode material such as LiCoO ₂ or LiCoMn ₂ O ₄ and a negative electrode material such as LiC ₆ Ti ₅ O ₁₂ are carbon conductive. It is configured to be applied together with auxiliary materials and binders.

  The inner ends (5a) and (5b) of the pair of lead terminals (5) and (6) are fixed to the positive electrode (1) and the negative electrode (2) of the electrochemical element (10) by welding or the like, respectively. Are connected to each other.

  The exterior films (4) and (4) are made of a square moisture-proof laminate material. Of the four sides, three sides (4a) to (4c) are welded to form a bag, and the remaining one side However, it is configured as a seal portion (4d) and is sealed by welding after the electrochemical element (10) and the like are accommodated. In the present invention, of the four sides around the exterior film, two sides are welded, and the remaining two sides are configured as a positive electrode lead terminal seal portion and a negative electrode lead terminal seal portion, respectively. You may make it do.

  Needless to say, in the present invention, the shape, size and the like of the exterior films (4) and (4) are not limited and can be arbitrarily changed.

  The exterior film (4) has a three-layer laminated structure as shown in FIG. 4, and the inner surface layer (41) provided on the inner surface side is a heat-adhesive (thermoplastic) synthetic resin such as high-density polyethylene, low It is composed of a material selected from density polyethylene, linear low density polyethylene, polyethylene ionomer, polyolefin resin such as polypropylene, and the like.

  The outer surface layer (43) provided on the outer surface side is made of polyester such as polyethylene terephthalate (PET) having electrical insulating properties, or polyamide such as nylon.

  The intermediate layer (42) provided between the inner surface layer (41) and the outer surface layer (43) is made of a metal foil, for example, an aluminum foil or a SUS foil. This intermediate layer (42) effectively prevents moisture from entering from outside and evaporation of the electrolyte from inside.

  The outer surface layer (43) has a role of securing mechanical strength and protecting the intermediate layer (42).

  Of the lead terminals (5) and (6), the positive electrode side is made of a metal conductor such as aluminum or titanium, and the negative electrode side is made of a metal conductor such as copper, nickel, or nickel-plated copper. . Needless to say, the materials of the lead terminals (5) and (6) are not limited to those described above.

  Since the thin battery of this embodiment is suitable for a large current, a large current flows through the lead terminals (5) and (6). For this reason, it is necessary to reduce the resistance of the current flowing through the lead terminals (5) and (6). As the lead terminals (5) and (6), those having a large cross-sectional area, that is, those having a large thickness are used. For example, in this embodiment, it is preferable to set the thickness of the lead terminals (5) and (6) to 0.2 to 1.5 mm. That is, when the lead terminals (5) and (6) are too thin, the resistance when a large current flows is increased, which is not preferable. Conversely, when the thickness is too thick, there is a possibility that wrinkles or the like may occur when the exterior film (4) or the sealing film (7) is brought into close contact, which is not preferable.

  In the present invention, the width and length of the lead terminals (5) and (6) may be appropriately set according to the performance of the electrochemical device and the like while taking the thickness into consideration.

  As shown in FIGS. 5 to 8, the sealing film (7) has a three-layer structure with a thickness of 0.08 to 0.25 mm. This sealing film (7) is welded by a hot roll, a flat hot plate or the like with the portions corresponding to the seal portions (4d) in the lead terminals (5) and (6) sandwiched from both sides.

  In the sealing film (7), the outermost layer (73) in direct contact with the inner surface layer (41) of the outer film (4) has compatibility (adhesiveness) with the inner surface layer (41) of the outer film (4). In consideration of the same type of synthetic resin of the same material, such as polypropylene, polyethylene (high density polyethylene, low density polyethylene, linear low density polyethylene, polyethylene vinyl acetate copolymer resin, ionomer, etc.), etc. Olefin resins can be used preferably. Needless to say, the outermost layer (73) is not required to be acid-modified as described later.

The innermost layer (71) in direct contact with the lead terminals (5) and (6) is made of a material excellent in adhesiveness with the metal material constituting the lead terminals (5) and (6), for example, maleic anhydride group or acrylic acid ( Examples thereof include olefin resins modified with an ester.

  The intermediate insulating layer (72) provided between the innermost layer (71) and the outermost layer (73) in the sealing film (7) is made of a material having a structure unique to the present invention.

  The intermediate insulating layer (72) needs to use a material having a melting point higher than that of the innermost layer (71), and preferably a material having a melting point higher by 5 ° C. or more.

Specifically, as the intermediate insulating layer (72), an olefin resin modified with polyvinylidene chloride, maleic acid , or acrylic acid can be suitably used, thereby increasing the flexibility of the sealing film (7) as a whole. (Becomes weak), familiarity to the lead terminals (5) and (6) is improved, and the sealing film (7) is closely attached to the entire circumference of the lead terminals (5) and (6) In addition, the sealing performance can be remarkably improved. Needless to say, the effect of improving the sealing property can be surely obtained in any of the lead terminals (5) and (6) of the positive electrode and the negative electrode.

  For reference, when a known material such as polyethylene terephthalate or high melting point homopolypropylene is used as the intermediate insulating layer of the sealing film, the flexibility is insufficient (because the waist is too hard), leading to the lead terminal. As a result, the sealing film cannot be reliably adhered over the entire circumference of the lead terminal, and it may be difficult to obtain sufficient sealing performance.

  Moreover, it is preferable to set the thickness of an intermediate | middle insulating layer (72) to 20 to 60% with respect to the full thickness of a sealing film (7). That is, when the thickness of the intermediate insulating layer (72) is too thick, the adhesiveness to the lead terminals (5) and (6) and the exterior film (4) is lowered, whereas when the thickness is too thin, the lead terminal ( 5) At the time of heat welding at the time of sealing between (6) and the exterior film (4), it may be difficult to maintain insulation between the two.

Furthermore, in this embodiment, the sealing film (7) has sufficient flexibility. Specifically, the tensile strength (F5 value) when stretched by 5% is adjusted to 15 N / mm ² or less. It is necessary to adopt what was done. That is, in the sealing film (7), when the tensile strength when stretched by 5% exceeds 15 N / mm ² , the flexibility (leading property) to the lead terminal deteriorates due to lack of flexibility. It may be difficult to obtain a sufficient sealing property.

  In the present invention, the sealing film (7) is not limited to a three-layer structure, and may have a multilayer structure of four or more layers.

  An example of a manufacturing procedure in the thin battery configured as described above is as follows. First, the sealing films (7) and (7) are welded and fixed to the lead terminals (5) and (6) in a state where the sealing films (7) and (7) are sandwiched from both sides at the portions corresponding to the seal portions (4d). Subsequently, the lead terminals (5) and (6) are fixed to the electrochemical element (10) by welding.

  On the other hand, the laminate material for the exterior film cut out into two rectangular shapes is opposed to the inner surface layers (41) and (41) sides, and the three sides (4a) to (4c) are thermally welded. Bag-shaped exterior films (4) and (4) are prepared.

  And the electrochemical element (10) to which the lead terminal (5) (6) was connected is accommodated in the exterior film (4) (4).

  Then, in a state where the lead terminals (5) and (6) are sandwiched between the sealing films (7) and (7) by the sealing portions (4d) and (4d) of the exterior films (4) and (4), the sealing portion ( 4d) The whole area of (4d) is thermally welded together. Thereby, the electrochemical device (thin battery) in which the electrochemical element (10) is housed in a sealed state in the exterior film (4) is produced.

  Needless to say, in the present invention, the method for producing an electrochemical device (thin battery) is not particularly limited.

  As shown in FIG. 6 and the like, the electrochemical device obtained in this way is sealed because the sealing film (7) directly covered with the lead terminals (5) and (6) has sufficient flexibility. The film (7) adheres to the entire circumference of the lead terminals (5) and (6) without a gap, and sufficient sealing properties can be obtained. Accordingly, it is possible to reliably prevent problems such as leakage of the electrolyte and to improve durability such as improvement of battery life.

  The outermost layer (73) of the sealing film (7) uses a material excellent in adhesiveness with the inner surface layer (41) of the exterior film (4), and the innermost layer (71) is a lead terminal (5). (6) Since the material excellent in adhesiveness is used, the adhesiveness between the sealing film (7) and the exterior film (4) can be improved, and the sealing film (7) and the lead terminal (5) (6) It is possible to improve both the adhesiveness and the sealing property.

  The use of the electrochemical device of the present invention is not limited, but in particular, a power battery for large-sized, large-capacity, high-power density, large-current applications, for example, an automobile battery for an electric vehicle or a hybrid vehicle. Etc. can be suitably used. Needless to say, the electrochemical device of the present invention can be employed without any problem even in a small-sized device such as a cell phone battery.

  Next, examples and comparative examples using the thin battery having the above-described configuration will be described.

  In the examples and comparative examples, the configuration (material, size, etc.) of the lead terminals (5), (6) and the configuration (material, size, etc.) of the exterior film (4) made of the packaging laminate material are all the same. It is as follows.

  First, the lead terminals (5) and (6) were prepared for the positive electrode made of aluminum having a thickness of 0.2 mm and a width of 50 mm, and for the negative electrode, made of Ni plated copper having a thickness of 0.2 mm and a width of 50 mm.

  In the laminate material for the exterior film (4), the outer surface layer (43) is a biaxially stretched nylon (ONY) film having a thickness of 40 μm, the intermediate layer (42) is an aluminum foil having a thickness of 15 μm, and the inner surface layer (41). However, the thing of the 3 layer structure comprised by the 30-micrometer-thick unstretched polypropylene (CPP) film was prepared.

  The sealing film (7) has a three-layer structure having an outermost layer (73), an intermediate insulating layer (72) and an innermost layer (71), and the layers (71) to (73) are shown in Table 1. We prepared what was made up of.

<Example 1>
As shown in Table 1, as the sealing film (7), the innermost layer (71) is made of acrylic acid-modified polypropylene having a thickness of 30 μm and a melting point of 134 ° C., and the intermediate insulating layer (72) has a thickness of 40 μm and a melting point. It was made of polyvinylidene chloride at 145 ° C., and the outermost layer (73) was made of maleic acid- modified polypropylene having a thickness of 30 μm and a melting point of 134 ° C. In this sealing film (7), the tensile strength (F5 value) when stretched by 5% was 13.6 N / mm ² .

  The sealing film (7) having this configuration was coated on the required positions (positions corresponding to the seal portions) of the lead terminals (5) and (6) by thermal welding.

On the other hand, the three sides excluding the seal portion (4d) in the laminate material for the exterior film cut out in a square shape are welded using a bar-shaped mold connected to a heater, so that a bag-shaped exterior film (4 ) Was produced. 10 g of a pseudoelectrolytic solution having a composition of “EC: DEC = 1: 1 + 1 mol LiPF ₆ ” was introduced into the exterior film (4), and then a predetermined amount of the lead terminals (5) and (6) was inserted, and the exterior film (4 In the state where the lead terminals (5) and (6) are sandwiched by the sealing portion (4d) of the sealing portion (4d), the sealing portion (4d) is welded together to form a sealed state. An electrochemical device sample was obtained.

<Example 2>
As shown in Table 1, as the sealing film (7), the innermost layer (71) is made of maleic acid- modified polypropylene having a thickness of 30 μm and a melting point of 134 ° C., and has an F5 value of 13.2 N / mm ² . Otherwise, the electrochemical device sample of Example 2 was obtained in the same manner as in Example 1 above.

<Example 3>
As shown in Table 1, as the sealing film (7), the innermost layer (71) is made of maleic acid- modified polypropylene having a thickness of 30 μm and a melting point of 134 ° C., and the intermediate insulating layer (72) has a thickness of 40 μm and a melting point. An electrochemical device sample of Example 3 was obtained in the same manner as in Example 1 except that polyvinylidene chloride at 165 ° C. and having an F5 value of 13.9 N / mm ² was used.

<Example 4>
As shown in Table 1, as the sealing film (7), the innermost layer (71) is made of maleic acid- modified polypropylene having a thickness of 20 μm and a melting point of 134 ° C., and the intermediate insulating layer (72) has a thickness of 60 μm and a melting point. It is made of maleic acid- modified polypropylene at 168 ° C., and the outermost layer (73) is made of maleic acid- modified polypropylene having a thickness of 20 μm and a melting point of 134 ° C., and has an F5 value of 14.8 N / mm ^2. In the same manner as in Example 1, the electrochemical device sample of Example 4 was obtained.

<Example 5>
As shown in Table 1, as the sealing film (7), the innermost layer (71) is made of maleic acid- modified polypropylene having a thickness of 30 μm and a melting point of 143 ° C., and the intermediate insulating layer (72) has a thickness of 40 μm and a melting point. It is made of polyvinylidene chloride at 148 ° C., the outermost layer (73) is made of polypropylene (random polymer) with a thickness of 30 μm and a melting point of 145 ° C., and F5 value is 14.1 N / mm ² , otherwise In the same manner as in Example 1, the electrochemical device sample of Example 5 was obtained.

<Example 6>
As shown in Table 1, as the sealing film (7), the innermost layer (71) is made of maleic acid- modified polypropylene having a thickness of 30 μm and a melting point of 134 ° C., and the intermediate insulating layer (72) has a thickness of 40 μm and a melting point. Made of maleic acid- modified polypropylene at 168 ° C, outermost layer (73) is made of polypropylene (block polymer) with a thickness of 30 µm and melting point of 160 ° C, F5 value is 14.9 N / mm ² , other than that Obtained an electrochemical device sample of Example 6 in the same manner as in Example 1 above.

<Example 7>
As shown in Table 1, as the sealing film (7), the innermost layer (71) is made of maleic acid- modified polypropylene having a thickness of 40 μm and a melting point of 134 ° C., and the intermediate insulating layer (72) has a thickness of 20 μm and a melting point. Made of maleic acid- modified polypropylene at 168 ° C., outermost layer (73) is made of maleic acid- modified polypropylene with a thickness of 40 μm and melting point of 134 ° C., and F5 value is 12.1 N / mm ² , otherwise In the same manner as in Example 1, the electrochemical device sample of Example 7 was obtained.

<Comparative Example 1>
As shown in Table 1, as the sealing film (7), the innermost layer (71) is made of acid-modified polypropylene having a thickness of 30 μm and a melting point of 134 ° C., and the intermediate insulating layer (72) has a thickness of 40 μm and a melting point of 264. The outermost layer (73) is made of acid-modified polypropylene having a thickness of 30 μm and a melting point of 134 ° C., and the F5 value is 65.0 N / mm ^2. In the same manner as in Example 1, an electrochemical device sample of Comparative Example 1 was obtained.

<Comparative example 2>
As shown in Table 1, as the sealing film (7), the innermost layer (71) is made of acid-modified polypropylene having a thickness of 30 μm and a melting point of 134 ° C., and the intermediate insulating layer (72) has a thickness of 40 μm and a melting point of 272. The outermost layer (73) is made of acid-modified polypropylene having a thickness of 30 μm and a melting point of 134 ° C., and the F5 value is 83.0 N / mm ^2. The electrochemical device sample of Comparative Example 2 was obtained in the same manner as Example 1.

<Comparative Example 3>
As shown in Table 1, as the sealing film (7), the innermost layer (71) is made of acid-modified polypropylene having a thickness of 30 μm and a melting point of 134 ° C., and the intermediate insulating layer (72) has a thickness of 40 μm and a melting point of 165. The outermost layer (73) is made of polypropylene (random polymer) having a thickness of 30 μm and a melting point of 145 ° C., and the F5 value is 18.3 N / mm ^2. Obtained an electrochemical device sample of Comparative Example 3 in the same manner as in Example 1 above.

<Evaluation of sealing performance>
In each of the samples of Examples 1 to 7 and Comparative Examples 1 to 3 thus obtained, in the sealing film covering region (region corresponding to the seal portion 4d: heat welding region) in the lead terminals (5) and (6), respectively. The lead terminals (5) and (6) were cut in a direction perpendicular to the length direction, and the cross sections thereof were observed.

  As a result, in the samples of Examples 1 to 7, as shown in FIG. 9, between the lead terminals (5) and (6) and the sealing film (7), particularly the side edges of the lead terminals (5) and (6). There are no gaps or other cavities formed in the vicinity of the part, and the sealing film (7) is firmly adhered to the entire circumference of the lead terminals (5) and (6) without any gaps, so that sufficient sealing properties are obtained. Has been confirmed.

  On the other hand, in the samples of Comparative Examples 1 to 3, as shown in FIG. 10, the side edges of the lead terminals (5) and (6) between the lead terminals (5) and (6) and the sealing film (7). The cavity (8) was formed in the part. That is, in the samples of Comparative Examples 1 to 3, the sealing film (7) is not closely adhered to the entire periphery of the lead terminals (5) and (6) as compared with the example, and the sealing property It was confirmed that it was inferior.

<Durability evaluation>
For each sample of Examples 1 to 7 and Comparative Examples 1 to 3, the mass (weight) was measured, and then left to stand so that the tab portion (lead terminal lead-out portion) faced downward, at a temperature of 85 ° C. A storage test was conducted for 1 week. And after completion | finish of a preservation | save test, mass was measured and the mass difference before and behind a preservation | save test was measured. The results are shown in Table 2.

  As is clear from Table 2, in the samples of Examples 1 to 7, no mass difference was observed before and after the storage test, and even under a long-term severe environment, there was no problem such as electrolyte leakage, and the long-term It was confirmed that a stable sealing property was obtained and the durability was excellent.

  On the other hand, in the samples of Comparative Examples 1 to 3, the mass decreased after the storage test, and it is recognized that electrolyte leakage occurred during the storage test period. That is, it was confirmed that the samples of Comparative Examples 1 to 3 were difficult to obtain long-term stable sealing properties and inferior in durability as compared with the samples of Examples.

In this example, a specific electrolyte and a non-aqueous electrolyte were used. However, in the present invention, the configuration in the electrochemical element such as a battery is not limited, and a known one is appropriately selected and used. can do. For example, as the electrolyte, in addition to KiPF ₆ , LiBF ₄ and a mixture thereof can be used.

  The electrochemical device of the present invention can be used as a thin battery or a thin capacitor.

DESCRIPTION OF SYMBOLS 1 ... Positive electrode 2 ... Negative electrode 3 ... Electrolyte 4 ... Exterior film 41 ... Inner surface layer (inner surface side)
4d: exterior film sealing portion 5, 6: lead terminals 5a, 6a: inner end (one end) of the lead terminal
5b, 6b ... Outer end (other end) of the lead terminal
7 ... Sealing film 71 ... Innermost layer 72 ... Intermediate insulating layer 73 ... Outermost layer 10 ... Electrochemical element

Claims (7)

An exterior film made of a heat-adhesive synthetic resin on the inner surface side, an electrochemical element housed in the exterior film, an inner end portion electrically connected to the electrochemical element, and an outer end portion external to the exterior film A lead terminal disposed on the lead film; and a sealing film that covers a part of the lead terminal, and the lead film is sandwiched by the seal portion of the lead film, and the lead film is sandwiched between the lead film and the lead film. An electrochemical device to which a seal portion of
The sealing film is provided between the outermost layer having compatibility with the inner surface side of the exterior film, the innermost layer having adhesiveness with the lead terminal, the outermost layer and the innermost layer, and from the innermost layer. Also has an intermediate insulating layer with a high melting point,
The sealing film is adjusted to have a tensile strength of 15 N / mm ² or less when stretched by 5% ,
The intermediate insulating layer is made of polyvinylidene chloride;
The electrochemical device , wherein the thickness of the intermediate insulating layer is 20 to 60% with respect to the total thickness of the sealing film .   The electrochemical device according to claim 1, wherein the difference between the melting point of the innermost layer and the melting point of the intermediate insulating layer in the sealing film is 5 ° C or higher. The electrochemical device according to claim 1 or 2 , wherein the lead terminal has a thickness of 0.2 to 1.5 mm. When the thickness of the sealing film electrochemical device according to claim 1 is 0.08～0.25Mm. It is comprised by the electrochemical device of any one of Claims 1-4 ,
A thin battery characterized in that the electrochemical element is constituted by a battery power generation element including at least a positive electrode, a negative electrode, and an electrolyte interposed between both positive and negative electrodes. A step of preparing a bag-shaped exterior film in which an inner surface side is made of a heat-adhesive synthetic resin and a peripheral portion excluding a seal portion is fused;
A step of preparing a lead terminal in which an electrochemical element is electrically connected to one end and a part thereof is covered with a sealing film;
While accommodating the electrochemical element in the exterior film, with the other end portion of the lead terminal arranged outside, while sandwiching the lead terminal through the sealing film by the seal portion of the exterior film, Welding the seal portion of the exterior film,
As the sealing film, the outermost layer having compatibility with the inner surface side of the exterior film, the innermost layer having adhesion with the lead terminal, the outermost layer and the innermost layer, and the innermost layer from the innermost layer And an intermediate insulating layer having a high melting point, the tensile strength when stretched by 5% is adjusted to 15 N / mm ² or less , and the intermediate insulating layer is made of polyvinylidene chloride, An electrochemical device having a thickness of the intermediate insulating layer of 20 to 60% with respect to the total thickness . An exterior film made of a heat-adhesive synthetic resin on the inner surface side, an electrochemical element housed in the exterior film, an inner end portion electrically connected to the electrochemical element, and an outer end portion external to the exterior film In the electrochemical device in which the seal portion of the exterior film is welded in a state where the lead terminal is sandwiched by the seal portion of the exterior film, the lead film is disposed between the exterior film and the lead terminal. A sealing film covering a part of the lead terminal so as to be interposed therebetween,
An outermost layer having compatibility with the inner surface side of the outer film, an innermost layer having adhesiveness with the lead terminal, an intermediate insulation provided between the outermost layer and the innermost layer and having a higher melting point than the innermost layer And having a layer
The tensile strength when stretched 5% is adjusted to 15 N / mm ² or less ,
The intermediate insulating layer is made of polyvinylidene chloride;
The sealing film in an electrochemical device , wherein the thickness of the intermediate insulating layer is 20 to 60% with respect to the total thickness .

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