JP2008052932A - Flat electrochemical cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a flat electrochemical cell which does not cause a decrease or failure in insulation even if a crack or pinhole is formed on inner edge corners of adjacent peripheral thermoadhesive portions when the peripheral edge thermoadhesive portions are folded to reduce the overall size of the electrochemical cell. <P>SOLUTION: An electrochemical element having positive and negative electrodes is interposed between two outer sheathes. Metal terminals connected to the positive and negative electrodes are projected out of the outer sheathes, and the electrochemical element is sealed inside the peripheral thermoadhesive portions to form the flat electrochemical cell having a square shape in a flat view. The inner edge corners of adjacent peripheral thermoadhesive portions are chamfered by corner thermoadhesive portions. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention accommodates an electrochemical element composed of a positive electrode, a negative electrode, a separator, an electrolyte, and the like, and is moisture-proof and sealed by thermally bonding a peripheral portion in a state in which a metal terminal from each electrode protrudes outward. The present invention relates to a flat electrochemical cell excellent in puncture resistance, insulation, heat resistance and cold resistance.

  In general, flat electrochemical cells are characterized by their small size and light weight, and are used for various applications because of their high volumetric efficiency and weight efficiency. For example, there are a lithium secondary battery and an electric double layer capacitor used in electronic devices such as a personal computer (PC) and a mobile phone.

  The exterior body is roughly divided into a metal can sealed by metal bonding and a flexible exterior material thermally bonded and sealed, but the ease of taking out and sealing the metal terminal, Alternatively, since it has flexibility, it can be shaped to fit the appropriate space of the electronic device or electronic component, and the shape of the electronic device or electronic component itself can be freely designed to some extent, so further downsizing For reasons such as being able to reduce the weight, exterior materials in which metal foils such as plastic films and aluminum are laminated have come to be used. Hereinafter, the flat electrochemical cell of the present invention will be described as a lithium secondary battery, but the present invention includes an electric double layer capacitor.

  And, for the exterior material, physical properties required as an electrochemical cell, for example, a lithium secondary battery will be described as an example, moisture resistance, sealing performance, puncture resistance, insulation, heat resistance / cold resistance, Since the electrolyte resistance (electrolytic solution resistance), corrosion resistance (resistance to hydrofluoric acid generated by electrolyte degradation and hydrolysis), etc. are required as indispensable ones, Generally composed of a base material layer for preventing energization with the outside, a metal foil layer such as aluminum for ensuring moisture proofing, and an inner layer for ensuring sealability while having excellent adhesion to metal terminals It is what is done.

  A lithium secondary battery is a battery made of a solid polymer, a gel-like polymer, a liquid or the like as an electrolyte and generating electricity by movement of lithium ions, and includes a positive electrode / negative electrode active material made of a polymer. . The structure of the lithium secondary battery is as follows: positive electrode current collector (aluminum) / positive electrode active material layer (polymeric positive electrode material such as metal oxide, carbon black, metal sulfide, electrolyte, polyacrylonitrile) / electrolyte (propylene carbonate, ethylene Carbonate electrolyte such as carbonate, dimethyl carbonate, ethylene methyl carbonate, inorganic solid electrolyte composed of lithium salt, gel electrolyte) / negative electrode active substance layer (lithium metal, alloy, carbon, electrolyte, polymer negative electrode material such as polyacrylonitrile) ) / An electrochemical element (battery element) made of a negative electrode current collector (copper) and an exterior body composed of an exterior material for housing them.

  As a form of the lithium battery, the above-described exterior material is formed into a bag shape as shown in FIG. 4 (a) at the peripheral heat-bonding portion [FIG. 4 (a) is a pillow type packaging bag, but three-way It may be a packaging bag of a type, a four-way type, etc.), and although not shown, the metal terminal connected to each of the positive electrode and the negative electrode of the electrochemical element is stored in a state protruding outward, and the opening The bag type shown in FIG. 4 (b) that is thermally bonded and sealed, or the above-described exterior material is press-molded as shown in FIG. 5 (a) to form a recess, and this recess is not shown. Accommodates the metal terminal connected to each of the positive electrode and the negative electrode of the electrochemical element in a state of protruding outward, and the recess is formed by the sheet-shaped exterior material (cover) that is separately prepared but not shown. Do not seal and seal the four edges The there is a molding type shown in Figure 5 (b). In addition, although not shown in the drawing type, the four peripheral edges are formed by press-molding as shown in FIG. 5A in place of the sheet-shaped exterior material (lid) covering the recess. There is also a molding type in which recesses are formed on both sides sealed by thermal bonding. Although not shown, the exterior material in which the recesses are formed and the exterior material (cover body) in which the recesses are formed by sheet forming or press molding do not have to be separate and may be integrated. . 4 and 5 are forms of the lithium battery of the present invention. 4 and 5, symbol A indicates an exterior material, symbol D indicates a lithium battery, symbol P indicates an inner edge corner of the peripheral thermal bonding portion, symbol S indicates a peripheral thermal bonding portion, and symbol T indicates a metal terminal.

  In any of the above-described lithium batteries, when the electrochemical element (battery element) is sealed with an exterior material, the electrochemical element and the metal terminal connected to each of the positive electrode and the negative electrode are projected to the outside and the exterior It is necessary to seal by thermally bonding in a state where the metal terminal is sandwiched between materials. For this purpose, the inner layer of the outer packaging material is heat-adhered and sealed with a heat-adhesive resin having good adhesion to the metal, for example, an acid-modified olefin resin graft-modified with an unsaturated carboxylic acid, or The above-mentioned acid modification that uses a general olefin resin (linear or branched olefin resin composed of carbon and hydrogen) that has poor adhesion to metal for the inner layer and has good adhesion to the metal A method of sealing by thermally bonding an adhesive film for sealing a metal terminal portion made of an olefin resin between the metal terminal and the inner layer is generally employed. The latter method is mainly used because it is easy to obtain and it is easy to prevent a short circuit between the metal terminal and the metal foil layer in the layer structure of the exterior material.

  The molded type secondary battery described in Patent Document 2 is tighter (tight state) than the secondary battery composed of the bag type described in Patent Document 1 in the electrochemical type (battery element) and the like. Therefore, there is an advantage that the volume energy density can be improved, and there is an advantage that an electrochemical element or the like can be easily stored, and the molding type has become mainstream.

  And, the above-described molded type secondary battery is usually stored in an outer case such as plastic and used as a battery pack in order to obtain higher safety, but when stored in the outer case, In the molded type secondary battery, the four peripheral thermal bonding portions S shown in FIG. 5B are bent toward the concave portion, and the four corner portions protruding in a triangular shape are folded between the peripheral thermal bonding portion S and the concave portion. It is folded in between and stored in the outer case in a state of reduced bulk (for example, see FIGS. 4 and 5 of Patent Document 3).

In the molded type secondary battery in which the peripheral thermal bonding portion S is bent in order to reduce the bulk, stress is applied to the inner edge corners (four locations indicated by reference sign P in FIG. 5B) of the adjacent peripheral thermal bonding portion S. Therefore, cracks and pinholes may be generated in the inner layer of this part. This part is in contact with the electrolyte solution, and the electrolyte solution penetrates from this part to lower the insulation, and the electrolyte reaches the metal layer of the exterior material and causes insulation failure to function as a battery. There is a possibility that the problem of not fulfilling the above may occur.
JP-A-9-213285 JP 2001-229888 A JP 2001-256933 A

  Therefore, the present invention provides a decrease in insulation or poor insulation even when cracks or pinholes occur at the inner edge corners of adjacent peripheral heat-bonded portions when the peripheral heat-bonded portions are bent to reduce the bulk. It is an object of the present invention to provide a flat type electrochemical cell in which no generation occurs.

  In order to achieve the above object, the inventor of the present invention provides an electrochemical element having a positive electrode and a negative electrode interposed between two exterior members and connected to the positive electrode and the negative electrode, respectively. In a flat battery having a rectangular shape in plan view, in which the formed metal terminal protrudes outward and the electrochemical element is sealed with a peripheral thermal bonding portion, the inner edge corner of the adjacent peripheral thermal bonding portion is formed by a corner thermal bonding portion. It is characterized by chamfering.

  Further, the present invention according to claim 2 is the flat electrochemical cell according to claim 1, wherein at least a constant region including the inner edge corner or the inner edge corner of the peripheral thermal bonding portion is missing. It is a feature.

  Further, the present invention according to claim 3 is the flat electrochemical cell according to claim 1, wherein at least one of the exterior members is substantially surrounded by an inner edge of the peripheral thermal bonding portion and the corner thermal bonding portion. A recess for accommodating an electrochemical element having a shape-shaped opening is formed.

  According to a fourth aspect of the present invention, there is provided the flat electrochemical cell according to the first aspect, wherein the two outer packaging materials are connected via one end side.

  Moreover, this invention of Claim 5 is a flat type electrochemical cell in any one of Claims 1-4. WHEREIN: The said exterior material is at least a base material layer, aluminum foil, a chemical conversion treatment layer, and an adhesive layer. The heat-adhesive resin layer is a laminate in which the heat-adhesive resin layers are sequentially laminated.

  In the flat electrochemical cell of the present invention, the inner edge corner portion of the adjacent peripheral thermal bonding portion is chamfered by the corner thermal bonding portion, so that the electrochemical element is accommodated in order to reduce the bulk of the flat electrochemical cell. Even if the peripheral heat-bonding part is bent and molded to the side, the corner heat-bonding part provides the space for storing the electrochemical element and the inner edge corner part separated by the corner heat-bonding part. Even if cracks or pinholes occur in the inner edge corners of the peripheral thermal bonding part, the electrolyte does not penetrate into this part, and it is possible to reliably prevent deterioration of insulation and insulation failure. It is effective.

The above invention will be described in detail below with reference to the drawings.
1A and 1B schematically show a first embodiment of a flat electrochemical cell according to the present invention. FIG. 1A is a plan view, FIG. 1B is a sectional view taken along line XX of FIG. 2) is a cross-sectional view taken along line YY of FIG. 2, FIG. 2 is an enlarged explanatory view of the main part corresponding to FIG. 1 (a), schematically showing a second embodiment of the flat electrochemical cell according to the present invention, and FIG. It is a figure which shows one Example of the layer structure of the exterior material used for the flat type electrochemical cell concerning this. In the figure, 1, 1 'is a flat type electrochemical cell, 2 is a shaping | molding container main body, 3 is a lid | cover Body, F is a flange part, G is an exterior material, K is a corner thermal bonding part, P is an inner edge corner part of a peripheral thermal bonding part, S is a peripheral thermal bonding part, T is a metal terminal, and U is a recess.

  1A and 1B schematically show a first embodiment of a flat electrochemical cell according to the present invention. FIG. 1A is a plan view, FIG. 1B is a sectional view taken along line XX of FIG. ), The flat electrochemical cell 1 has a concave portion U having a substantially octagonal cross section, and a flange portion F having a rectangular outer shape on the periphery of the concave portion U. 2 and a lid member 3 of approximately the same size as the molded container body 2, and an electrochemical element (not shown) having a positive electrode and a negative electrode are accommodated in the concave portion U of the molded container body 2. A metal terminal T connected to each of the positive electrode and the negative electrode protrudes outward from the flange portion F, is covered with the lid body 3 and has a substantially rectangular peripheral heat-bonding portion S provided on the flange portion F and the adjacent one. An inner edge corner portion P of the peripheral heat bonding portion S is sealed with a corner heat bonding portion K. The peripheral thermal bonding portion S and the corner thermal bonding portion K have been described as being formed separately, but in fact, the peripheral thermal bonding portion S and the corner thermal bonding portion K are heated by an integral hot plate or the like. It is to be glued. The concave portion U is formed by press molding (cold molding) using a male mold and a female mold.

  In the flat electrochemical cell 1 configured as described above, the peripheral thermal bonding portion S is bent toward the concave portion U of the molded container body 2 and the four corner portions protruding in a triangular shape are bent in order to reduce the bulk. It is folded between the peripheral thermal bonding portion S and the concave portion U, and is housed in an outer case such as plastic in this state and used as a battery pack.

  By the way, the flat electrochemical cell 1 of the present invention has a peripheral edge thermal bonding portion S adjacent to the inner edge corner portion P isolated from the electrolyte contained in the concave portion U by the corner thermal bonding portion K. The thermal bonding portion S is folded and the four corner portions protruding in a triangular shape are folded between the peripheral thermal bonding portion S and the concave portion U, and stress is applied to the inner edge corner portion P. Even if cracks or pinholes occur in the inner layer, the inner edge corner P does not come into contact with the electrolytic solution, so that the insulating property does not deteriorate and insulation failure does not occur.

  FIG. 2 is an enlarged explanatory view of a main part corresponding to FIG. 1 (a), schematically showing a second embodiment of the flat electrochemical cell according to the present invention, and the flat electrochemical cell 1 ′ is the flat type. In the four corner portions of the electrochemical cell 1, the inner edge corner portion P is cut leaving the corner thermal bonding portion K with a constant width m. Same as chemical cell 1. By configuring in this way, the peripheral heat-bonding portion S is bent toward the concave portion U of the molded container body 2 and the four corner portions protruding in a triangular shape are bent in order to reduce the bulk. When the flat electrochemical cell 1 is folded between the concave portion U and the concave portion U, the portion protruding in a triangular shape at the time of folding serves as a resistance at the time of folding, and the protrusion does not fit well after the folding, Since the flat electrochemical cell 1 ′ does not have the inner edge corner portion P, it is easy to bend and there is no portion protruding in a triangular shape, so that it fits well. The constant width m is preferably at least 3 mm from the viewpoint of obtaining stable heat seal strength.

  Further, in FIG. 2, although the inner edge of the corner thermal bonding portion K is shown as a straight line, it is not shown in the figure, but is cut so as to have an arc shape protruding toward the inner edge corner P side. It may be. In this case, it is sufficient that the constant width m has an arc shape of at least 3 mm. In addition to cutting the four corners and removing the inner edge corner P where stress is concentrated when bent, as shown above, although not shown, a certain region including the inner edge corner P is formed into a circular shape or the like. A notch may be provided, and a cut may be provided in a-(minus) shape or + (plus) shape including the inner edge corner portion P. 1 and 2 show the flat electrochemical cell 1 and 1 ′ having the concave portion U on one side, the configuration may be such that there is no concave portion U, and the flange portion F is the boundary. The structure which has the recessed part U in both may be sufficient, and also the molding container main body 2 and the cover body 3 may use a separate exterior material, and use the exterior material integrated through one side. It may be.

  Next, the exterior material of the flat electrochemical cell 1, 1 'will be described. FIG. 3 is a diagram schematically showing an embodiment of a layer structure of an exterior material used in a flat electrochemical cell according to the present invention. The exterior material G includes a base material layer 10, an adhesive layer 20, and a chemical conversion treatment. The layer 30, the aluminum foil 40, the chemical conversion treatment layer 30, the adhesive layer 50, and the thermoadhesive resin layer 60 are laminated in order.

  The base material layer 10 is provided for the purpose of protecting the aluminum foil 40 from external force and improving the puncture resistance against piercing from the outside. The base layer 10 is stretched in the biaxial direction from the viewpoint of excellent mechanical strength. A polyester film, a polyamide film, or a laminate thereof can be exemplified. Examples of the polyester film include films made of polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polycarbonate, and the like, and examples of the polyamide film include nylon 6, nylon 6,6, nylon 6, A film composed of 10 etc. can be mentioned. The thickness of the base material layer is suitably 6 μm or more. The reason for this is that if the thickness is less than 6 μm, there may be pinholes in itself, and the protective effect of the aluminum foil against external force will be reduced. This is because breakage is likely to occur and molding defects are likely to occur, and more preferably 12 μm or more. In addition, if the substrate layer is thicker than 25 μm, whether it is a single layer or multiple layers of the above-mentioned film, no significant effect is observed in terms of protecting the aluminum foil against external force, and the volume and weight energy density are reduced. In addition, it is desirable not to use it from the viewpoint of cost effectiveness. In addition, the above-described polyester film and polyamide film may be subjected to easy adhesion treatment such as corona discharge treatment, ozone treatment, and plasma treatment on a necessary surface.

  The aluminum foil 40 is provided to prevent water vapor from entering the inside of the flat electrochemical cell from the outside. In consideration of ensuring the water vapor barrier property and processing suitability during processing, 20 Those having a thickness of up to 200 μm are suitable. If the thickness is less than 20 μm, the pinhole of the aluminum foil alone is concerned, and the risk of intrusion of water vapor increases, and if the thickness exceeds 200 μm, a remarkable effect is recognized on the pinhole of the aluminum foil. In addition, it is desirable that further improvement of the water vapor barrier property cannot be expected, the processability is inferior, the volume and the weight energy density are lowered, and the cost effectiveness is not used.

  In addition, the aluminum foil 40 contains 0.3 to 9.0% by weight, preferably 0.7 to 2.0% by weight of iron, and has excellent ductility as compared with the one not containing iron, and is resistant to bending. It is preferable to use an aluminum foil containing iron in order to obtain a uniform molded product with little occurrence of pinholes and no uneven thickness especially during press molding. If the iron content is less than 0.3% by weight, no effect is observed in prevention of pinholes and spreadability, and if the iron content exceeds 9.0% by weight, the flexibility as an aluminum foil is hindered. However, the moldability decreases.

  Although the aluminum foil 40 is manufactured by cold rolling, its flexibility, waist strength and hardness change under annealing (so-called annealing treatment) conditions, but the aluminum foil used in the present invention is annealed. An aluminum foil that tends to be softer than the hard-treated product that has been annealed to some degree or completely is preferable. The aluminum foil 40 used in the present invention is preferably 8000 to 3000 series.

  Next, the chemical conversion treatment layer 30 will be described. The chemical conversion treatment layer 30 prevents the aluminum foil 40 from being corroded by the electrolytic solution or hydrofluoric acid generated by hydrolysis of the electrolytic solution and firmly adheres the aluminum foil 40 to the adhesive layers 20 and 50 described later. It is provided to prevent delamination due to hydrofluoric acid generated by hydrolysis of the electrolytic solution or electrolytic solution and to prevent delamination during press molding.

  The chemical conversion treatment layer 30 is formed by chromium-based chemical conversion treatment such as chromate chromate treatment, phosphoric acid chromate treatment, and coating-type chromate treatment, or non-chromium (coating-type) chemical conversion treatment such as zirconium, titanium, and zinc phosphate. Although formed on the surface of the aluminum foil 40, a coating type chemical conversion treatment is suitable because continuous treatment is possible and a water washing step is unnecessary and the treatment cost can be reduced. The treatment solution may be treated with a conventionally known chromate treatment solution containing a hexavalent chromium compound, but is environmentally friendly and does not easily cause a decrease in the adhesive strength between the layers as time passes. Specifically, it is preferably formed using a treatment liquid containing an aminated phenol polymer, a trivalent chromium compound, and a phosphorus compound.

First, the aminated phenol polymer will be described. A well-known thing can be widely used as an aminated phenol polymer, for example, aminated phenol heavy which consists of a repeating unit represented by following formula (1), (2), (3), (4). Coalescence can be mentioned. X in the formula represents a hydrogen atom, a hydroxyl group, an alkyl group, a hydroxyalkyl group, an allyl group or a benzyl group. R ₁ and R ₂ represent a hydroxyl group, an alkyl group, or a hydroxyalkyl group, and may be the same group or different groups.

In the following formulas (1) to (4), examples of the alkyl group represented by X, R ₁ and R ₂ include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, C1-C4 linear or branched alkyl groups, such as a tert- butyl group, can be mentioned. Examples of the hydroxyalkyl group represented by X, R ₁ and R ₂ include a hydroxymethyl group, a 1-hydroxyethyl group, a 2-hydroxyethyl group, a 1-hydroxypropyl group, a 2-hydroxypropyl group, 3- C1-C4 straight or branched chain in which one hydroxy group such as hydroxypropyl group, 1-hydroxybutyl group, 2-hydroxybutyl group, 3-hydroxybutyl group, 4-hydroxybutyl group is substituted An alkyl group can be mentioned. X in the following formulas (1) to (4) is preferably any one of a hydrogen atom, a hydroxyl group, and a hydroxyalkyl group.

Further, the aminated phenol polymer represented by the following formulas (1) and (3) is an aminated phenol containing about 80 mol% or less of repeating units, preferably about 25 to about 55 mol% of repeating units. It is a polymer. The number average molecular weight of the aminated phenol polymer is preferably about 500 to about 1 million, more preferably about 1000 to about 20,000. The aminated phenol polymer is produced by, for example, polycondensing a phenol compound or naphthol compound and formaldehyde to produce a polymer composed of repeating units represented by the following (1) to (3). It is produced by introducing a water-soluble functional group (—CH ₂ NR ₁ R ₂ ) using formaldehyde and an amine (R ₁ R ₂ NH). The aminated phenol polymer can be used singly or in combination of two or more.

  Next, the trivalent chromium compound will be described. As the trivalent chromium compound, known compounds can be widely used. For example, chromium nitrate, chromium fluoride, chromium sulfate, chromium acetate, chromium oxalate, chromium biphosphate, chromic acetyl acetate, chromium chloride, sulfuric acid Potassium chromium etc. can be mentioned, Preferably they are chromium nitrate and chromium fluoride.

  Next, a phosphorus compound is demonstrated. As a phosphorus compound, a well-known thing can be used widely, For example, condensed phosphoric acids, such as phosphoric acid and polyphosphoric acid, these salts, etc. can be mentioned. Here, as said salt, alkali metal salts, such as ammonium salt, sodium salt, potassium salt, can be mentioned, for example.

And as said chemical conversion treatment layer formed using the processing liquid containing an aminated phenol polymer, a trivalent chromium compound, and a phosphorus compound, about 1 to about 200 mg of an aminated phenol polymer per 1 m ² , It is appropriate that the trivalent chromium compound is contained in a proportion of about 0.5 to about 50 mg in terms of chromium, and the phosphorus compound is contained in a proportion of about 0.5 to about 50 mg in terms of phosphorus. More preferably, about 5.0 to 150 mg, the trivalent chromium compound is contained in a proportion of about 1.0 to about 40 mg in terms of chromium, and the phosphorus compound is contained in a proportion of about 1.0 to about 40 mg in terms of phosphorus. In this case, the drying temperature is 150 to 250 ° C., preferably 170 to 250 ° C., and the heat treatment (baking treatment) is appropriate.

  Moreover, as a formation method of the said chemical conversion treatment layer, the said process liquid should just be formed by selecting suitably the well-known coating methods, such as a bar-coat method, a roll-coating method, a gravure coating method, and an immersion method. Further, before forming the chemical conversion treatment layer, the surface of the aluminum foil is previously subjected to a known degreasing treatment method such as an alkali dipping method, an electrolytic cleaning method, an acid cleaning method, an electrolytic acid cleaning method, or an acid activation method. It is preferable to perform the treatment from the viewpoint that the function of the chemical conversion treatment layer can be maximized and can be maintained for a long period of time. The chemical conversion treatment layer 30 on the base material layer 10 side is necessarily provided in order to prevent delamination during press molding when the flat electrochemical cell is a molding type. When G is used without being molded, it is not necessary to provide it.

  Next, the adhesive layers 20 and 50 will be described. First, the adhesive layer 50 is provided to firmly bond the chemical conversion treatment layer 30 of the aluminum foil 40 and the thermal adhesive resin layer 60 described later, and the adhesive layer 50 is formed. Examples of the resin include, for example, a polyolefin resin graft-modified with an unsaturated carboxylic acid, an acid-modified polyolefin resin such as a copolymer of ethylene or propylene and acrylic acid, or methacrylic acid, particularly preferably an unsaturated carboxylic acid. In the method of forming the adhesive layer 50, the resin described above is melt-extruded on the surface of the chemical conversion treatment layer 30 of the aluminum foil 40 using a T-die extruder, which will be described later. So-called sandwich laminating, in which resin films constituting the heat-adhesive resin layer 60 are laminated It may be formed by laminating by the film forming method, or may be laminated on the surface of the chemical conversion treatment layer 30 of the aluminum foil 40 by the thermal lamination method using the film made of the resin as described above. It is. In this case, the thickness of the adhesive layer 50 is 5 to 20 μm, preferably 10 to 15 μm. If the thickness is less than 5 μm, sufficient laminate strength cannot be obtained, and if it exceeds 20 μm, moisture permeation from the end face increases. This is because the performance as a flat electrochemical cell may be deteriorated.

Further, if the resin forming the adhesive layer 20 is exemplified, for example, a well-known two-component curable dry lamination adhesive composed of a main component such as polyester, polyether or polyurethane can be exemplified. As the method for forming the adhesive layer 20, a composition in which an isocyanate compound is blended with the above main agent is applied to the base material layer 10 by a known application method such as a gravure coating method or a roll coating method, and then dried. It can be formed by laminating the surface of the chemical conversion layer 30 of the foil 40 by a so-called dry lamination method. The coating amount after drying of the adhesive layer 20 is suitably 3.0 to 5.0 g / m ² .

  Next, the resin that forms the thermal adhesive resin layer 60 will be described. As the resin for forming the thermal adhesive resin layer 60, the electrochemical element of the flat electrochemical cell and the metal terminal connected to each of the positive electrode and the negative electrode are sandwiched and protruded to the outside and thermally bonded. The resin type differs depending on whether or not a metal terminal portion sealing adhesive film is interposed between the heat-adhesive resin layer 60 and the metal terminal during sealing. Since acid-modified olefin resin is usually used as the metal terminal sealing adhesive film, low density polyethylene, medium density polyethylene, high density polyethylene, wire are used when the metal terminal sealing adhesive film is interposed. General olefins such as simple resins or mixtures of propylene resins such as homopolypropylene, ethylene-propylene copolymer, and ethylene-propylene-butene copolymer Resin (linear or branched olefin resin composed of carbon and hydrogen) may be selected as appropriate, and these general olefin resins may be formed into a film and sandwich lamination method. , Dry lamination, thermal lamination, etc. In addition, the heat-adhesive resin layer 60 is exemplified as a resin for forming the adhesive layer 50, and the acid-modified polyolefin resin and the above-described low density polyethylene, medium density polyethylene, high density polyethylene, linear low density polyethylene, The chemical conversion treatment of the aluminum foil 40 with an ethylene resin such as an ethylene-butene copolymer, or a single or mixture of propylene resins such as a homopolypropylene, an ethylene-propylene copolymer, and an ethylene-propylene-butene copolymer. The adhesive layer 50 and the heat-adhesive resin layer 60 may be formed at the same time by co-extrusion with the layer 30, or the acid-modified polyolefin resin exemplified above as the resin for forming the adhesive layer 50 and the low density described above. Polyethylene, medium density polyethylene, high density polyethylene, linear low density polyethylene, ethylene Co-extruded films by coextrusion of propylene resins such as ethylene-butene copolymers, homopolypropylene, ethylene-propylene copolymers, and ethylene-propylene-butene copolymers. However, this may be formed by laminating the chemical conversion treatment layer 30 of the aluminum foil 40 by a thermal lamination method.

  Further, when no adhesive film for sealing the metal terminal portion is interposed, the acid-modified polyolefin resin exemplified as the resin for forming the adhesive layer 50, for example, a polyolefin resin graft-modified with an unsaturated carboxylic acid, ethylene or An acid-modified polyolefin resin such as a copolymer of propylene and acrylic acid or methacrylic acid, particularly preferably a polyolefin resin graft-modified with an unsaturated carboxylic acid can be used. In this case, the adhesive layer 50 is also used. Is also good. The thickness of the heat-adhesive resin layer 60 is 10 to 100 μm, preferably 30 to 50 μm. If the thickness is less than 10 μm, sufficient adhesive strength cannot be obtained when heat-bonding, resulting in a problem in sealing performance. If the thickness exceeds 100 μm, there is no significant effect on the sealing performance when heat-adhering and sealing, and the total thickness increases to reduce the volume and weight energy density and cost-effectiveness. It is preferable not to use from the viewpoint. In the case where the heat-adhesive resin layer 60 is composed of a film, a necessary surface may be subjected to easy adhesion treatment such as corona discharge treatment, ozone treatment, or plasma treatment.

Next, the present invention will be described in more detail with reference to the following examples.
First, an aluminum foil (40 μm) having a chemical conversion treatment layer on both surfaces by chemical conversion treatment (phosphoric acid chromate treatment) on both sides with a chemical conversion treatment liquid consisting of three components of phenol resin, chromium fluoride (trivalent) compound and phosphoric acid in advance. And the other surface of the aluminum foil after laminating a biaxially stretched nylon film (hereinafter referred to as ON) having a thickness of 25 μm via a two-component curable polyurethane adhesive. And an acid-modified polypropylene resin [unsaturated carboxylic acid graft-modified random polypropylene grafted with an unsaturated carboxylic acid (hereinafter referred to as PPa)] and polypropylene [random copolymer (hereinafter referred to as PP)] were coextruded. When a two-layer coextruded film [PPa 15 μm / PP 30 μm] is placed so that the PPa surface is located on the aluminum foil side, After heating so that the surface of the chemical conversion treatment layer becomes 120 ° C. and laminating by the thermal lamination method, it is further post-heated so as to become 180 ° C., and ON 25 μm / adhesive layer / chemical conversion treatment layer / aluminum foil 40 μm / chemical conversion treatment layer / An exterior material (laminate) having a PPa of 15 μm / PP of 30 μm was produced.

  The exterior material (laminated body) produced above is cut to produce a strip of 175 × 125 mm, and a straight consisting of a rectangular male mold of 124 × 74 mm and a female mold with a clearance of 0.5 mm between the male mold Use a mold (male chamfer with 5mm corner shape, ridge line R is 1.5mm, female corner shape is 5.5mm beveled, ridge line R is 1.5mm) on the male side The strip is placed on the female mold so that the heat-adhesive resin layer is located, and the strip is pressed with a pressing pressure (surface pressure) of 0.5 MPa, and cold-molded to a molding depth of 5 mm. A press-molded container main body having a rectangular shape of 124 × 74 mm having a flange portion at the periphery and a recess having a depth of 5 mm was produced. A plastic molded product having a size corresponding to the press-molded container body is placed in the recess of the press-molded container body, and the recess is covered with strip pieces approximately the same size as the separately prepared press-molded container body so that the four peripheral edges are substantially coincident with each other. In addition, the 3 peripheral edges are 2 mm away from the side surface of the recess and completely heat-bonded with a width of 7 mm. Next, the remaining 1 peripheral edge is degassed and temporarily heat-bonded in the vacuum chamber, and then removed from the vacuum chamber and temporarily removed. The same peripheral edge of the same heat-bonded part is 2 mm away from the side surface of the recess and is completely heat-bonded to a width of 7 mm. Three chemical cellular specimens were prepared.

[Comparative Example 1]
Straight mold used in Example 1 (C-chamfer with male corner shape of 5 mm, ridge line R is 1.5 mm, female corner shape is sloped with 5.5 mm, ridge line R is 1.5 mm) Instead of using a straight mold (male corner R is 3 mm, ridge line R is 1.5 mm, female corner R is 3.5 mm, ridge line R is 1.5 mm) A strip piece [same exterior material (laminate) as in Example 1] is placed on the female mold so that the heat-adhesive resin layer is positioned on the plate, and the strip piece is pressed with a pressing pressure (surface pressure) of 0.5 MPa. Thus, a press-molded container main body having a rectangular shape of 124 × 74 mm having a flange portion on the four peripheral edges and a concave portion having a depth of 5 mm was manufactured by cold forming to a forming depth of 5 mm. A plastic molded product having a size corresponding to the press-molded container main body is put in the concave portion of the press-molded container main body, and a strip of the same size as the separately prepared press-molded container main body (same exterior material (laminate) as in Example 1). The recesses are covered so that the four peripheral edges substantially coincide with each other, and the peripheral edges of the three peripheral edges are 2 mm away from the side surfaces of the concave parts and are completely heat-bonded with a width of 7 mm, and then the remaining one peripheral edge is deaerated in the vacuum chamber. In addition, after temporarily heat-bonding, three flat electrochemical cell specimens were prepared by taking out from the vacuum chamber and completely heat-bonding the same one peripheral edge 2 mm away from the side surface of the recess and 7 mm wide. In both Example 1 and Comparative Example 1, heat sealing conditions for complete thermal bonding were performed at 190 ° C., 0.5 MPa, and 3 seconds using hot plates coated with fluororesin on the top and bottom.

  About the flat electrochemical cell-like test specimens of Example 1 and Comparative Example 1 produced above, “the vicinity of the side surface of the concave portion is bent 90 degrees to the concave portion side, returned to the original, and bent to 90 degrees on the opposite side to the concave portion side. Perform the operation “Restore” on all four edges and use this as one cycle to open a hole in the flat electrochemical cell test specimen for testing and air enters the cell, and the flat electrochemical cell test The number of cycles until the vacuum state in the body was impaired was evaluated for each of Example 1 and Comparative Example 1, and the results are summarized in Table 1.

  As is clear from Table 1, compared to Comparative Example 1, Example 1 could be a flat electrochemical cell-like test body in which bending pinholes were much less likely to occur.

BRIEF DESCRIPTION OF THE DRAWINGS (a) is a top view schematically showing 1st Embodiment of the flat type electrochemical cell concerning this invention, (b) is XX sectional drawing of (a), (c) is Y of (a). FIG. It is principal part expansion explanatory drawing corresponding to FIG. 1 (a) which shows 2nd Embodiment of the flat type electrochemical cell concerning this invention illustratively. It is a figure which shows typically one Example of the laminated constitution of the exterior material used for the flat type electrochemical cell concerning this invention. It is a figure explaining one Example of the form of a lithium battery. It is a figure explaining the other Example of the form of a lithium battery.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 1 'flat type electrochemical cell 2 Molding container main body 3 Cover body F Flange part G Exterior material K Corner | angular part thermal bonding part P Inner edge corner | angular part of a peripheral thermal bonding part S Perimeter thermal bonding part T Metal terminal U Recess

Claims (5)

An electrochemical element having a positive electrode and a negative electrode is interposed between two outer packaging materials, and metal terminals connected to the positive electrode and the negative electrode are protruded to the outside so that the electrochemical element is sealed with a peripheral heat bonding portion. A flat electrochemical cell having a rectangular shape in plan view, wherein an inner edge corner portion of the adjacent peripheral thermal bonding portion is chamfered by a corner thermal bonding portion. 2. The flat electrochemical cell according to claim 1, wherein at least a certain region including the inner edge corner portion or the inner edge corner portion of the peripheral thermal bonding portion is missing. A recess for accommodating an electrochemical element having a substantially shaped opening surrounded by an inner edge of the peripheral thermal bonding portion and the corner thermal bonding portion is formed in at least one of the exterior materials. The flat electrochemical cell according to claim 1. 2. The flat electrochemical cell according to claim 1, wherein the two exterior members are connected to each other through one end side. The said exterior material consists of a laminated body by which the base material layer, the aluminum foil, the chemical conversion treatment layer, the contact bonding layer, and the thermoadhesive resin layer were laminated | stacked in order. A flat electrochemical cell according to claim 1.

Images