JP5194922B2 - Packaging materials for electrochemical cells - Google Patents

Description

  The present invention relates to a packaging material for electrochemical cells that exhibits stable heat resistance, electrolytic solution resistance, gas permeability resistance, and moldability.

The lithium ion battery is also referred to as a lithium secondary battery, and includes a liquid, gel-like, or polymer polymer electrolyte, and a positive electrode / negative electrode active material made of a polymer polymer. In this lithium ion battery, the lithium atom (Li) in the lithium transition metal oxide, which is the positive electrode active material, is charged as lithium ion (Li ⁺ ) during charging and enters the carbon layer of the negative electrode (intercalation). This is a battery in which charge / discharge reaction proceeds when ions (Li ⁺ ) are separated from the carbon layer (deintercalation) and move to the positive electrode to become the original lithium compound. From the nickel-cadmium battery and the nickel-hydrogen battery The output voltage is high, the energy density is high, and the apparent discharge capacity is reduced by repeating shallow discharge and recharging, so that there is no so-called memory effect.

  In addition, the configuration of the lithium ion battery is composed of a positive electrode current collector / positive electrode active material layer / electrolyte layer / negative electrode active material layer / negative electrode current collector and an outer package that wraps these, and as a packaging material for forming the outer package, Metal cans that are made by pressing a metal into a cylindrical shape or a rectangular parallelepiped shape have been used.

  However, since the outer wall of the container is rigid, the shape of the battery itself is limited, and there is no degree of freedom in shape because it is necessary to design the hardware side to match the battery. Instead, multilayer films tend to be used as packaging materials.

  FIG. 8 is a cross-sectional view showing a layer structure of a conventional packaging material 30. As shown in FIG. 8, the conventional packaging material 30 includes at least a base material layer 31, a metal foil layer 32, and a thermal adhesive resin layer 35. The chemical conversion treatment layer 33 is formed on the surface of the metal foil layer 32, and the metal foil layer 32 and the heat-adhesive resin layer 35 are bonded by an acid-modified polyolefin layer 34. Further, the base material layer 31 and the metal foil layer 32 are bonded by an adhesive layer 37. Also, there is a pouch type in which the packaging material 30 is formed in a bag shape and the battery body is accommodated, or an embossed type battery exterior body in which the packaging material 30 is pressed to form a recess and the battery body is accommodated in the recess. It is formed.

  FIG. 9 is a perspective view of a conventional pouch-type lithium ion battery 41, and FIG. 10 is an exploded perspective view showing the pouch-type lithium ion battery 41 shown in FIG. 9 in an exploded manner. As shown in FIGS. 9 and 10, the pouch-type lithium ion battery 41 has the innermost heat-adhesive resin layer 35 (see FIG. 8) overlapped with each other, and a heat seal portion 40 a that is a peripheral portion of the exterior body 40. The pouch-type exterior body 40 is formed by heat sealing, the lithium ion battery main body 42 is accommodated in the exterior body 40, the opening is heat sealed, and the lithium ion battery main body 42 is hermetically stored.

  FIG. 11 is a perspective view of a conventional embossed type lithium ion battery 51, and FIG. 12 is an exploded perspective view showing the embossed type lithium ion battery 51 shown in FIG. As shown in FIGS. 11 and 12, the embossed type lithium ion battery 51 accommodates a lithium ion battery main body 52 inside a tray 50t in which an embossed portion is formed, and the thermoadhesive resin layer 35 between the tray 50t and the sheet 50s. (Refer to FIG. 8) The two lithium ion battery main bodies 52 are placed inside the embossed type outer package 50 composed of the tray 50t and the sheet 50s by superimposing each other and heat-sealing the heat seal portion 50a which is the peripheral portion of the outer package 50. Store sealed.

  The lithium ion battery bodies 42 and 52 include a positive electrode made of a positive electrode active material and a positive electrode current collector, a negative electrode made of a negative electrode active material and a negative electrode current collector, and an electrolyte filled between the positive electrode and the negative electrode (both A cell (power storage unit) including a cell (not shown), and metal terminals 44 and 54 that are connected to a positive electrode and a negative electrode in the cell and protrude from the exterior bodies 40 and 50 to the outside.

  13 is a perspective view of a conventional embossed type lithium ion battery 61, and is a cross-sectional view taken along the line B-B 'of the lithium ion battery 61 of FIG. As shown in FIG. 14, the outer package 60 has the innermost thermal adhesive resin layers 35 overlapped with each other, and the outer periphery of the outer package 60 is heat sealed to bond the outer periphery of the outer package (heat seal portion 60 a). The lithium ion battery main body 62 is hermetically housed in the first region 60b other than the heat seal. However, in the first region 60 b, the lithium ion battery main body 62 generates heat due to long-term use or rapid charging of the lithium ion battery 61, and one of the thermoadhesive resin layers 35 disposed in the innermost layer of the exterior body 60. Some parts melted. At this time, the electrolyte filled in the exterior body 60 permeates into the metal foil layer 32 from a part of the molten heat-adhesive resin layer 35, and the lithium ion battery 61 may cause a short circuit.

  On the other hand, when a resin having excellent heat resistance is used for the heat-adhesive resin layer 35 so that the heat-adhesive resin layer 35 is not easily melted, it is necessary to set a high temperature during heat sealing. There was a problem that the production efficiency was lowered. Therefore, in order to solve these problems, conventionally, a packaging material in which an intermediate layer made of a biaxially stretched film having excellent heat resistance such as polyethylene terephthalate is interposed between the heat-adhesive resin layer 35 and the metal foil layer 32 has been used. It was proposed.

  In Patent Document 1, an aluminum foil that is a metal foil layer and a thermoplastic resin film that is a thermoadhesive resin layer are bonded together by an adhesive composition containing polyolefin polyol and a polyfunctional isocyanate curing agent as essential components. Packaging materials have been proposed.

On the other hand, as shown in FIG. 14, water vapor gas permeates into the exterior body 60 from the acid-modified polyolefin layer 34 and the heat-adhesive resin layer 35 on the end surface of the heat-sealed exterior body 60. When the water vapor gas penetrates into the exterior body 60, the electrolyte filled in the exterior body 60 reacts with the permeated water vapor gas, and hydrogen fluoride gas is generated, which may cause the exterior body 60 to burst. For this reason, the acid-modified polyolefin layer 34 and the heat-adhesive resin layer 35 are made of a resin that is difficult to permeate water vapor gas and has excellent gas permeability, and between the metal foil layer 32 and the heat-adhesive resin layer 35. In addition, it was an effective method to prevent water vapor gas from permeating into the exterior body 60 from the end face of the exterior body 60 without providing an extra resin layer.
Japanese Patent Laid-Open No. 2005-63685

  However, when an intermediate layer made of a biaxially stretched film such as polyethylene terephthalate is interposed between the heat-adhesive resin layer 35 and the metal foil layer 32, a new adhesive layer for bonding the biaxially stretched film is provided. It was necessary to provide in. For this reason, there existed a problem that water vapor | steam gas became easy to osmose | permeate from the end surface of the newly provided adhesive bond layer. Furthermore, when a biaxially stretched film such as polyethylene terephthalate is interposed between the heat-adhesive resin layer 35 and the metal foil layer 32, the heat-adhesive resin layer 35 and the metal foil layer are embossed when the packaging material 30 is embossed. 32 is easily peeled off and the moldability is lowered. Moreover, the packaging material shown by patent document 1 uses the adhesive composition which has polyolefin polyol and a polyfunctional isocyanate hardening | curing agent as an essential component, such as the heat resistance of an exterior body, a moldability, gas-permeability resistance, etc. Although it is considered that the characteristics are improved, a sufficient effect to solve the above problem cannot be obtained.

  In addition to the case where the lithium ion battery main body 42, 52, 62 is accommodated in the outer body 40, 50, 60, the same applies to the case where an electrochemical cell main body such as a capacitor or an electric double layer capacitor is accommodated and hermetically sealed. There was a problem.

  Therefore, in view of the above problems, the present invention is used for an exterior body that hermetically houses an electrochemical cell body such as a lithium ion battery body, a capacitor, and an electric double layer capacitor, and has heat resistance, electrolyte resistance, and gas permeability resistance. An object of the present invention is to provide a packaging material for an electrochemical cell having excellent moldability.

  In order to achieve the above object, in the packaging material for an electrochemical cell according to the first configuration of the present invention, a positive electrode comprising a positive electrode active material and a positive electrode current collector, a negative electrode comprising a negative electrode active material and a negative electrode current collector, A base material layer that is used for an exterior body that houses an electrochemical cell body containing an electrolyte filled between the positive electrode and the negative electrode and heat seals a peripheral portion thereof to seal and house the electrochemical cell body inside And a packaging material for an electrochemical cell comprising a metal foil layer whose surface is subjected to chemical conversion treatment, an acid-modified polyolefin layer, and a heat-adhesive resin layer, and the metal foil. A heat resistant resin coating layer is formed on the surface of the layer, and the resin coating layer is formed excluding at least a part of a region to be heat sealed.

  The second configuration of the present invention is characterized in that, in the packaging material for electrochemical cells, the resin coating layer is formed by printing and applying a heat resistant resin in a predetermined pattern on the surface of the metal foil layer. And

  The third configuration of the present invention is characterized in that, in the electrochemical cell packaging material, the predetermined pattern is a dot pattern.

  The fourth configuration of the present invention is characterized in that, in the packaging material for electrochemical cells, the resin coating layer is made of a resin mainly composed of an epoxy resin.

  According to the first configuration of the present invention, since the resin coating layer is formed except for at least a part of the region to be heat-sealed, the packaging material for electrochemical cells of this configuration has a resin in the region to be heat-sealed. It has a region without a coating layer. Therefore, when the packaging material for an electrochemical cell of this configuration is heat-sealed, in the region where the resin coating layer is not interposed in the region to be heat-sealed, the sealing strength is not lowered and the gas permeability resistance is not lowered. In addition, the case where the resin coating layer is not formed in all regions of the heat seal region is most desirable from the viewpoint of seal strength and gas permeation resistance.

  Moreover, the packaging material for electrochemical cells of this structure has a resin coating layer interposed in a region other than the region to be heat sealed. Therefore, when an exterior body is formed using the electrochemical cell packaging material of this configuration, a metal foil layer in which a resin coating layer is formed is disposed inside the exterior body. Therefore, even when the electrochemical cell body including the electrolyte generates heat inside the outer package and the innermost heat-adhesive resin layer melts, the metal foil layer is protected by the heat-resistant resin coating layer. For this reason, it can prevent that an electrolyte contacts a metal foil layer and an electrochemical cell short-circuits. Thereby, the exterior body shape | molded using the packaging material for electrochemical cells of this structure has the outstanding insulation with respect to the heat_generation | fever inside an exterior body.

  In addition, since the resin coating layer is formed on the surface of the metal foil layer, it has less influence on the adhesion between the metal foil layer and the acid-modified polyolefin layer than when a heat-resistant resin film is interposed as an intermediate layer. For this reason, the packaging material for electrochemical use of this configuration does not deteriorate the press moldability.

  According to the second configuration of the present invention, in the packaging material for electrochemical cells, the resin coating layer is predetermined by forming a resin coating layer by printing and applying a heat resistant resin in a predetermined pattern on the surface of the metal foil layer. It can be accurately formed in the region. Therefore, by not forming the resin coating layer in the heat sealed region, it is possible to suppress a decrease in sealing strength and a decrease in gas permeability. Moreover, in the area | region which is not heat-sealed, the resin coating layer which has heat resistance can protect a metal foil layer by forming a resin coating layer, and it can prevent that an electrochemical cell short-circuits. Thereby, the exterior body shape | molded using the packaging material for electrochemical structures of this structure has the outstanding insulation with respect to the heat_generation | fever inside an exterior body.

  According to the third configuration of the present invention, in the packaging material for electrochemical cells, the resin coating layer is formed in a halftone dot pattern on the surface of the metal foil layer, so that the resin coating is applied to the heat sealed region and the non-heat sealed region. The layer can be formed uniformly. At this time, in the region to be heat-sealed, it is possible to suppress a decrease in sealing strength and a decrease in gas permeability resistance due to the portion where the resin coating layer is not formed. Moreover, in the area | region which is not heat-sealed, the resin coating layer can protect a metal foil layer by the part in which the resin coating layer was formed, and it can prevent that an electrochemical cell short-circuits. Thereby, the exterior body shape | molded using the packaging material for electrochemical structures of this structure has the outstanding insulation with respect to the heat_generation | fever inside an exterior body.

  In addition, by forming the resin coating layer on the surface of the metal foil layer in the form of a halftone dot, the resin coating layer can be uniformly formed in the heat-sealed region and the non-heat-sealed region. When forming an exterior body using the packaging material for a material, it is not necessary to determine a heat seal area | region previously. For this reason, the shape of an exterior body can be freely designed from the packaging material for electrochemical cells of this structure.

  According to the 4th structure of this invention, in the said packaging material for electrochemical cells, the heat resistance of a resin coating layer is securable by comprising a resin coating layer with resin which has an epoxy resin as a main component. Thereby, the exterior body shape | molded using the packaging material for electrochemical structures of this structure has the outstanding insulation with respect to the heat_generation | fever inside an exterior body.

  The present invention is a packaging material for electrochemical cells that is excellent in heat resistance, moldability, gas permeability resistance, and moldability. The packaging material for an electrochemical cell of the present invention will be described in more detail with reference to the drawings and the like using an exterior body formed using the packaging material. Note that description of parts common to those in FIGS. 8 to 14 in the conventional example is omitted.

  FIG. 1 is a cross-sectional view showing a partial layer structure of a packaging material 10 for an electrochemical cell according to the present invention. The materials of each layer constituting the packaging material 10 for an electrochemical cell according to the present invention will be described with reference to FIG. The packaging material 10 for an electrochemical cell of the present invention has a base material layer 11 as an outermost layer, a heat-adhesive resin layer 15 as an innermost layer, and a metal foil layer 12 disposed therebetween. The metal foil layer 12 is bonded via the acid-modified polyolefin layer 14. The base material layer 11 and the metal foil layer 12 are bonded via an adhesive layer 17. At this time, a chemical conversion treatment layer 13 is provided on the surface of the metal foil layer 12, and a resin coating layer 16 is formed thereon. In addition, the packaging material 10 for electrochemical cells of the present invention includes the above-described layers and includes the case where different layers are interposed between the respective layers in the technical scope of the present invention.

  2 shows a lithium ion battery 21 in which a lithium ion battery main body 22 (not shown in FIG. 2) is housed in a pouch-type outer package 20 formed using the packaging material 10 for electrochemical cells of the present invention. FIG. 3 is a perspective view, and FIG. 3 is a cross-sectional view taken along line AA ′ of the lithium ion battery 21 in FIG. 2. As shown in FIGS. 2 and 3, the outer package 20 is in a state where the metal terminal 24 is sandwiched, and the peripheral portion including the sandwiched portion is heat-sealed (hereinafter, the heat-sealed portion is referred to as a heat-sealed portion 20 a). The lithium ion battery main body 22 containing the electrolyte is hermetically housed inside the outer package 20. At this time, as shown in FIG. 3, in the heat seal portion 20 a, the resin coating layer 16 is not formed on the surface of the metal foil layer 12. On the other hand, the resin coating layer 16 is formed on the surface of the metal foil layer 12 in the first region 20b other than the heat seal portion 20a.

  Here, the resin coating layer 16 is formed by coating (coating) a resin having heat resistance on the surface of the metal foil layer 12. The resin coating layer 16 functions as a protective film on the surface of the metal foil layer 12. The resin coating layer 16 is formed at least on the surface of the metal foil layer 12 subjected to the chemical conversion treatment on the heat-adhesive resin layer 15 side, and an epoxy resin is applied to the surface of the metal foil layer 12 subjected to the chemical conversion treatment. Is formed by printing and applying a resin (hereinafter referred to as an epoxy resin) whose main component is a predetermined pattern. The thickness of the epoxy resin to be coated is about 1 μm.

  As shown in FIG. 3, in the first region 20 b where the resin coating layer 16 is formed on the surface of the metal foil layer 12, the lithium ion battery main body 2 generates heat inside the exterior body 20, and a part of the thermal adhesive resin layer 15 is formed. May melt. However, the resin coating layer 16 has a certain heat resistance and does not melt easily even when the heat resistant resin layer 15 is melted. Therefore, the electrolyte that has permeated into the metal foil layer 12 from the melted portion of the heat-adhesive resin layer is prevented from penetrating into the metal foil layer 12 by the resin coating layer 16. Thereby, the contact between the metal foil layer 12 and the electrolyte is prevented, and the occurrence of a short circuit in the lithium ion battery 21 can be suppressed. As mentioned above, the exterior body 20 formed using the packaging material 10 for electrochemical cells according to the present invention has excellent heat resistance against heat generation inside the exterior body 20. The resin coating layer 16 is formed by printing and applying a resin on the surface of the metal foil layer 12 and the layer thickness is as thin as about 1 μm. Therefore, when the electrochemical packaging material 10 is press-molded, the press moldability is almost lowered. do not do.

  On the other hand, in the heat seal part 20a where the resin coating layer 16 is not formed on the surface of the metal foil layer 12, the metal foil layer 12 is interposed between the acid-modified polyolefin layer 14 and the heat-adhesive resin layer 15 as shown in FIG. Is adhered. At this time, a chemical conversion treatment layer 13 (not shown in FIG. 3) is formed on the surface of the metal foil layer 12, and the chemical conversion treatment layer 13 stably adheres the acid-modified polyolefin layer 14 and the metal foil layer 12. The metal foil layer 12 and the heat-adhesive resin layer 15 have a function of preventing peeling or preventing the metal foil layer 12 from corroding. Therefore, as shown in FIG. 3, by not forming the resin coating layer 16 on the surface of the metal foil layer 12 in the heat seal portion 20a, the chemical conversion treatment layer 13 and the acid-modified polyolefin layer 14 formed on the surface of the metal foil layer 12 are formed. And the metal foil layer 12 can be prevented from corroding. In addition, since the resin coating layer 16 is not formed on the end surface of the exterior body 20 in the heat seal portion 20a, water vapor does not permeate from the end surface of the exterior body 20 into the exterior body 20 through the resin coating layer 16. Therefore, the gas permeation resistance of the outer package 20 does not decrease.

  FIG. 4 is a plan view showing an embodiment of the packaging material 10 for an electrochemical cell of the present invention molded into a pouch-type exterior body 20. As shown in FIG. 4, the pouch-type exterior body 20 is created by folding the packaging material 10 cut into rectangular sheet pieces in half and then heat-sealing the heat-sealing portion 20 a. At this time, the resin coating layer 16 is formed in the 1st area | region 20b except the heat seal part 20a.

  Here, the resin coating layer 16 is formed by printing and applying an epoxy resin in a predetermined pattern on the surface of the metal foil layer 12 that has been subjected to chemical conversion treatment in advance. The packaging material 10 for an electrochemical cell as shown in FIG. When the pouch-type exterior body 20 is formed using the above, it is necessary to cut the electrochemical cell packaging material 10 so that the region where the resin coating layer 16 is formed becomes the first region 20b.

  The resin coating layer 16 can be accurately formed in a predetermined region by using a method of forming the resin coating layer 16 by printing and applying an epoxy resin in a predetermined pattern on the surface of the metal foil layer 12. Therefore, the resin coating layer 16 can be accurately formed in the first region 20b excluding the heat seal part 20a, and a decrease in seal strength and a decrease in gas permeability resistance in the heat seal part 20a can be suppressed.

  FIG. 5 is a plan view showing a modification of the packaging material 10 for an electrochemical cell of the present invention formed on the pouch-type exterior body 20 shown in FIG. As shown in FIG. 2, the outer peripheral body 20 is in a state where the metal terminal 24 is sandwiched, and the peripheral portion (heat seal portion 20 a) including the sandwiched portion is heat sealed. Therefore, when the temperature inside the exterior body 20 rises due to overcharge or the like, the metal terminals 24 generate heat, and the sandwiched portion of the metal terminal 24 of the thermoadhesive resin layer 15 that is the innermost layer of the exterior body 20 melts. is there. Therefore, as shown in FIG. 5, by forming the resin coating layer 16 on the surface of the metal foil layer 12 in the second region 20c in the vicinity of the region where the metal terminal 24 is sandwiched, the sandwiched portion of the metal terminal 24 is melted. Even if it does, the resin coating layer 16 can prevent the contact with the metal terminal 24 and the metal foil layer 12, and can prevent the lithium ion battery 21 from short-circuiting. Therefore, even when a tab film (such as an acid-modified polypropylene single layer film) having no heat resistance is used for the sandwiched portion of the metal terminal 24, the exterior body 20 can be provided with heat resistance.

  6 is a plan view showing an embodiment of the packaging material 10 for an electrochemical cell of the present invention for forming a pouch-type exterior body 20, and FIG. 7 is an enlarged view of a partial region x in FIG. It is the top view shown typically. As shown in FIGS. 6 and 7, the packaging material 10 for an electrochemical cell according to the present embodiment has an epoxy resin mesh on the surface of the metal foil layer 12 in the first region 20 b excluding the heat seal portion 20 a and the heat seal portion 20 a. The resin coating layer 16 is formed by being uniformly printed and applied in the form of dots. In addition, as shown in FIG. 7, the epoxy resin printed and applied in a dot pattern alternately forms regions p where the epoxy resin is applied at regular intervals and regions n where the epoxy resin is not applied. Therefore, the packaging material 10 for electrochemical cells according to the present embodiment can suppress a decrease in seal strength and a decrease in gas permeability resistance due to the region n where no epoxy resin is applied in the heat seal region 20a. On the other hand, in the 1st field 20b except heat seal part 20a, contact with metal foil layer 12 and electrolyte can be prevented, and generation of a short circuit of lithium ion battery 21 can be controlled by field p where epoxy resin was applied. Thereby, the exterior body 20 formed using the packaging material 10 for an electrochemical cell according to the present embodiment prevents moisture gas from permeating from the outside at the end face of the exterior body 20 and generates heat inside the exterior body 20. Has a certain heat resistance. Moreover, since the area | region n to which the epoxy resin is not apply | coated is formed in the 1st area | region 20b in the packaging material 10 for electrochemical cells which concerns on this embodiment, the chemical conversion treatment layer 13 of the metal foil layer 12 surface is formed. As a result, the adhesion between the metal foil layer 12 and the acid-modified polyolefin layer 14 is stabilized.

  Moreover, as shown in FIG. 6, since the epoxy resin is uniformly printed and applied to the heat seal portion 20a and the second region 20b excluding the heat seal portion 20a, the packaging material for an electrochemical cell according to the present embodiment When the exterior body 20 is formed using 10, it is not necessary to cut the electrochemical cell packaging material 10 in accordance with the heat seal region 20 a designed in advance. For this reason, when creating the exterior body 20 from the electrochemical cell packaging material 10 of this configuration, the electrochemical cell packaging material 10 is cut in accordance with the shape of the exterior body 20, and the shape of the exterior body 20 is freely designed. can do.

  In addition, even if the region p where the epoxy resin is applied at regular intervals and the region n where the epoxy resin is not applied are alternately formed, the epoxy resin can be printed and applied in a predetermined pattern other than a dot pattern. The function of can be demonstrated.

  The heat-resistant resin used for the resin coating layer 16 is not limited to an epoxy-based epoxy resin, but is phenol-based, melamine-based, alkyd-based, polyimide-based, polyamide-imide-based, polyarylate-based, unsaturated polyester-based, polyurethane-based, liquid crystal It is also possible to use polymer-based or polyether ether ketone-based resins. Moreover, the heat resistance of an epoxy resin can also be improved by adding an alumina to an epoxy resin.

  Next, each layer which comprises the packaging material 10 for electrochemical cells which concerns on this invention shown in FIG. 1 is demonstrated concretely. The innermost heat-adhesive resin layer 15 is sandwiched and thermally bonded with the metal terminals 24 (see FIG. 2) of the lithium battery body 22 protruding outward. At this time, the kind of propylene constituting the thermal adhesive resin layer 15 differs depending on whether or not a metal terminal sealing adhesive film having metal adhesiveness is interposed between the thermal adhesive resin layer 15 and the metal terminal 24. . When an adhesive film for sealing metal terminals is interposed, a film made of a propylene-based resin alone or a mixture may be used. When an adhesive film for sealing metal terminals is not interposed, graft modification with unsaturated carboxylic acid is performed. It is necessary to use a film made of the acid-modified olefin resin.

  Polypropylene is suitably used as the heat-adhesive resin layer 15, but a single layer or a multilayer of linear low density polyethylene or medium density polyethylene, or a single resin composed of a blend resin of linear low density polyethylene and medium density polyethylene. Films consisting of layers or multilayers can also be used. Polypropylene can be classified into random propylene, homopropylene, block propylene and the like.

  Each of the above types of polypropylene, ie, random polypropylene, homopolypropylene, and block polypropylene, includes a low crystalline ethylene-butene copolymer, a low crystalline propylene-butene copolymer, and a three-component copolymer of ethylene, butene, and propylene. An antiblocking agent (AB agent) such as a polymer terpolymer, silica, zeolite, or acrylic resin beads, a fatty acid amide slip agent, or the like may be added.

  Further, the heat-adhesive resin layer 15 according to the present invention may be multilayered by combining the above-mentioned types of polypropylene layers as appropriate.

  Next, the base material layer 11 will be described. The base material layer 11 is generally made of stretched polyester or nylon film. At this time, examples of the polyester resin include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, copolymerized polyester, and polycarbonate. . Examples of nylon include polyamide resin, that is, nylon 6, nylon 6,6, a copolymer of nylon 6 and nylon 6,6, nylon 6,10, polymetaxylylene adipamide (MXD6), and the like.

In addition, the base material layer 11 can be laminated with films of different materials in addition to a polyester film or nylon film in order to improve pinhole resistance and insulation when used as a battery outer package. When making the base material layer 11 into a laminated body, a base material layer contains at least 1 resin layer of 2 or more layers, and the thickness of each layer is 6 micrometers or more, Preferably, it is 6-25 micrometers. Examples of laminating the base material layer include the following 1) to 7) although not shown.
1) Stretched polyethylene terephthalate / stretched nylon 2) Stretched nylon / stretched polyethylene terephthalate 3) Fluorine-based resin / stretched polyethylene terephthalate (Fluorine-based resin is formed into a film or dried after liquid coating)
4) Silicone resin / stretched polyethylene terephthalate (silicone resin is a film or formed by drying after liquid coating)
5) Fluorine-based resin / stretched polyethylene terephthalate / stretched nylon 6) Silicone-based resin / stretched polyethylene terephthalate / stretched nylon 7) Acrylic resin / stretched nylon (Acrylic resin is film-like or cured after drying by liquid coating)

  As shown in 3) to 7), mechanical suitability of packaging materials (stability of conveyance in packaging machines and processing machines), surface protection (heat resistance and electrolyte resistance), secondary processing In order to protect the base material layer 11 when reducing the frictional resistance between the mold and the base material layer 11 at the time of embossing or when an electrolytic solution adheres when the exterior body 20 for a lithium ion battery is made an embossed type. In addition, the base material layer 11 is multilayered, and a protective layer such as a fluorine resin layer, an acrylic resin layer, a silicone resin layer, a polyester resin layer, and a blend layer thereof on the surface of the base material layer (in FIG. 1, (Not shown) is preferably provided.

  The same effect can be obtained when stretched polybutylene terephthalate or polyethylene naphthalate is used in place of the stretched polyethylene terephthalate. The base material layer 11 is bonded to the metal foil layer 12 via the adhesive layer 17 by a dry lamination method or the like.

  Next, the metal foil layer 12 will be described. The metal foil layer 12 is a layer for preventing water vapor from entering the inside of the lithium ion battery from the outside, and stabilizes pinholes and processability (pouching, embossing formability) of the metal foil layer alone, In addition, in order to provide pinhole resistance, a metal such as aluminum or nickel having a thickness of 15 μm or more, or a film on which an inorganic compound such as silicon oxide or alumina is vapor-deposited may be mentioned. The aluminum has a thickness of 20 to 100 μm.

  Moreover, in order to improve the generation of pinholes and to make the outer body type of the lithium ion battery an embossed type, the material of aluminum used as the metal foil layer 12 is selected in order to prevent the occurrence of cracks in the embossing molding. It is desirable that the iron content is 0.3 to 9.0% by weight, preferably 0.7 to 2.0% by weight.

  As a result, compared with aluminum that does not contain iron, aluminum has good spreadability, and the occurrence of pinholes due to bending as an exterior body is reduced, and the side wall can be easily formed when embossing the packaging material. it can. In addition, when the iron content is less than 0.3% by weight, effects such as prevention of pinholes and improvement of embossing formability are not observed, and the iron content of aluminum exceeds 9.0% by weight. In this case, the flexibility as aluminum is hindered, and the bag-making property as a packaging material is deteriorated.

  In addition, aluminum produced by cold rolling changes its flexibility, waist strength and hardness under annealing (so-called annealing treatment) conditions, but the aluminum used in the present invention is harder than the non-annealed hard-treated product. Aluminum which tends to be soft with some or complete annealing is preferred.

  That is, the annealing conditions may be appropriately selected in accordance with processability (pouching, embossing). For example, in order to prevent wrinkles and pinholes during emboss molding, soft aluminum annealed according to the degree of molding can be used.

  Moreover, by performing a chemical conversion treatment on the front and back surfaces of aluminum that is the metal foil layer 12 to form the chemical conversion treatment layer 13, the adhesive strength with the adhesive can be improved.

  Next, the chemical conversion treatment layer 13 will be described. As shown in FIG. 1, the chemical conversion treatment layer 13 is formed on at least the surface of the metal foil layer 12 on the heat-adhesive resin layer 15 side. The chemical conversion treatment layer 13 can stably adhere the acid-modified polyolefin layer 14 and the metal foil layer 12 and prevent delamination of the metal foil layer 12 and the heat-adhesive resin layer 15. The chemical conversion treatment layer 13 also has a function of preventing the metal foil layer 12 from being corroded. Therefore, in order to stabilize the adhesiveness between the metal foil layer 12 and the heat-adhesive resin layer 15, the entire chemical conversion treatment surface is not applied with an epoxy resin, but as shown in FIG. It is desirable to form regions p where the epoxy resin is applied and regions n where the epoxy resin is not applied alternately to secure a region where the chemical conversion treatment layer 13 and the acid-modified polyolefin layer 14 are in contact with each other.

  Specifically, delamination between the metal foil layer 12 and the heat-adhesive resin layer 15 during embossing by forming an acid-resistant film such as phosphate, chromate, fluoride, triazine thiol compound, etc. And hydrogen fluoride produced by the reaction between the electrolyte and water in the lithium ion battery prevents the aluminum surface from being dissolved and corroded, especially the aluminum oxide present on the aluminum surface from being dissolved and corroded. Surface adhesion can be improved.

  The chemical conversion treatment layer 13 is made of a metal by chromium conversion treatment such as chromate chromate treatment, phosphoric acid chromate treatment, coating chromate treatment, or non-chromium (coating type) chemical conversion treatment such as zirconium, titanium, and zinc phosphate. Although it is formed on the surface of the foil layer 12, it is firmly bonded to the fluororesin, the point that it can be continuously processed and the water washing step is unnecessary, and the processing cost can be reduced. It is most preferable to treat with a treatment solution containing a coating type chemical conversion treatment, particularly an aminated phenol polymer, a trivalent chromium compound, and a phosphorus compound.

  Moreover, as a formation method of the chemical conversion treatment layer 13, what is necessary is just to select and shape | mold a process liquid, selecting well-known coating methods, such as a barcode method, a roll coat method, a gravure coat method, and an immersion method. Moreover, before forming the chemical conversion treatment layer 13, the surface of the metal foil layer 12 is previously treated by a known degreasing treatment method such as an alkali dipping method, an electrolytic washing method, an acid washing method, an acid activation method, or the like. However, it is preferable because the function of the chemical conversion treatment layer 13 can be expressed to the maximum and can be maintained for a long time.

  In addition, for each of the above layers, corona treatment, blast treatment, and oxidation treatment are appropriately performed for the purpose of improving and stabilizing film forming properties, lamination processing, and final product secondary processing (pouching, embossing). Surface activation treatment such as ozone treatment may be performed.

  Next, the acid-modified polyolefin layer 14 will be described. The acid-modified polyolefin layer 14 is a layer provided for bonding the metal foil layer 12 and the heat-adhesive resin layer 15. The acid-modified polyolefin layer 14 needs to be appropriately selected depending on the resin type used for the heat-adhesive resin layer 15. Modified polyolefin resins can be used, such as polyolefin resins graft-modified with unsaturated carboxylic acids, copolymers of ethylene or propylene and acrylic acid, or methacrylic acid, or metal-crosslinked polyolefin resins. 5% or more of a butene component, an ethylene-propylene-butene copolymer, an amorphous ethylene-propylene copolymer, a propylene-α-olefin copolymer, etc. may be added.

  Moreover, the acid-modified polyolefin layer 14 can provide the exterior body 20 which is more excellent in content resistance and adhesive strength by using acid-modified polypropylene.

When using acid-modified polypropylene,
(1) A homotype having a bigat softening point of 115 ° C or higher and a melting point of 150 ° C or higher,
(2) A copolymer of ethylene-propylene having a bigat softening point of 105 ° C or higher and a melting point of 130 ° C or higher (random copolymer type)
(3) A simple substance or a blended product obtained by acid-modified polymerization using an unsaturated carboxylic acid having a melting point of 110 ° C. or higher can be used.

  The present invention is not limited to the above-described embodiments, and various modifications are possible. Embodiments obtained by appropriately combining technical means disclosed in different embodiments are also included in the present invention. Included in the technical scope.

  Hereinafter, the operation and effect of the present invention will be specifically described with reference to examples. Example 1 evaluates the heat resistance and insulation in the sealing part after heat sealing of the packaging material for electrochemical cells in which a heat resistant resin coating layer is formed on the surface of the metal foil layer.

  The manufacturing method of the packaging material for electrochemical cells used in the present example is as follows. First, one surface of aluminum is subjected to chemical conversion treatment, and a stretched nylon film is applied to the surface not subjected to chemical conversion treatment with a two-component curable polyurethane adhesive. And bonded together by a dry laminating method. Next, acid-modified polypropylene (hereinafter abbreviated as acid-modified PP) is applied and baked on the surface subjected to chemical conversion treatment by a roll coating method, and a polypropylene film (hereinafter abbreviated as PP film, thickness 23 μm) is formed on the acid-modified PP surface. Were laminated by a thermal laminating method to obtain a packaging material for an electrochemical cell of Comparative Example 1.

In this example, the base layer is made of stretched nylon film (thickness 25 μm), the metal foil layer is made of aluminum (thickness 40 μm), and the chemical conversion treatment is a treatment comprising a phenol resin, a chromium fluoride compound, and phosphoric acid. The liquid was applied to the aluminum surface by a roll coating method, and baked under the condition that the film temperature was 90 ° C. or higher. Here, the application amount of chromium is 10 mg / m ² (dry weight), and the acid-modified PP is baked under the condition that the aluminum temperature is 140 ° C. or higher, and the application amount of the acid-modified PP is 3 g / m ² (dry). Weight).

  Next, as the aluminum of the packaging material obtained in Comparative Example 1 above, using the aluminum coated with an epoxy resin with a thickness of about 1 μm on the surface subjected to the chemical conversion treatment, the electrochemical cell according to the present invention 1 is used. A packaging material was obtained.

  Next, as aluminum of the packaging material obtained in Comparative Example 1 above, the present invention 2 is made by using aluminum coated with an epoxy resin added with alumina on a surface subjected to chemical conversion treatment to a thickness of about 1 μm. Such a packaging material for an electrochemical cell was obtained.

  Next, a film obtained by bonding a stretched nylon film (thickness 25 μm) to aluminum (thickness 40 μm) by a dry lamination method through a two-component curable polyurethane adhesive is cut to 60 mm × 100 mm to form an underlay film, The packaging material for electrochemical cells was cut into 40 mm × 50 mm sheet pieces. Next, the stretched nylon film surface of the underlying film and the PP film surface of the packaging material for electrochemical cells were brought into contact with each other, and a nickel tab (4 mm × 120 mm, thickness 70 μm) was sandwiched.

  Next, the positive electrode terminal is set on a nickel tab, the negative electrode terminal is set on aluminum constituting the packaging material for electrochemical cells, a voltage of 25 V is applied, and the seal temperature is 190 mm with a width of 7 mm including the portion sandwiching the nickel tab. Sealing was performed at a temperature of 15 ° C. and a sealing pressure of 15 MPa, and the time during which the resistance value was 1000 MΩ or less (hereinafter referred to as dielectric breakdown time) was measured. In this evaluation method, two samples each of Comparative Example 1 and Inventions 1 and 2 were prepared, and each evaluation was performed by the above evaluation method as a packaging material for an electrochemical cell. The results are shown in Table 1.

  As shown in Table 1, the packaging material for an electrochemical cell according to the present invention 1 or the present invention 2 containing aluminum coated with an epoxy resin or an epoxy resin added with alumina relates to Comparative Example 1 in which no epoxy resin is coated. It was found that the insulating material was superior to the packaging material for electrochemical cells.

  From this, it is thought that the exterior body produced using the packaging material for electrochemical cells containing the aluminum which coat | covered the surface with the epoxy resin or the epoxy resin which added the alumina is excellent in heat resistance.

Sectional drawing which shows the layer structure of the packaging material for electrochemical cells of this invention The perspective view of the lithium ion battery which used the packaging material for electrochemical cells of this invention for the exterior body Sectional drawing in A-A 'of the lithium ion battery shown in FIG. The top view which shows one Embodiment of the packaging material for electrochemical cells of this invention The top view which shows one Embodiment of the packaging material for electrochemical cells of this invention The top view which shows one Embodiment of the packaging material for electrochemical cells of this invention The top view which expands and shows a part of packaging material for electrochemical cells shown in FIG. Sectional drawing which shows the layer structure of the conventional packaging material for electrochemical cells A perspective view of a lithium ion battery using a conventional packaging material for electrochemical cells as an exterior body The exploded perspective view of the lithium ion battery shown in FIG. A perspective view of a lithium ion battery using a conventional packaging material for electrochemical cells as an exterior body The exploded perspective view of the lithium ion battery shown in FIG. A perspective view of a lithium ion battery using a conventional packaging material for electrochemical cells as an exterior body Sectional drawing in B-B 'of the lithium ion battery shown in FIG.

Explanation of symbols

10, 30 Electrochemical cell packaging material 11, 31 Base layer 12, 32 Metal foil layer 13, 33 Chemical conversion layer 14, 34 Acid-modified polyolefin layer 15, 35 Thermal adhesive resin layer 16 Resin coating layer 17, 37 Adhesion Agent layer 20, 40, 50, 60 Exterior body 20a, 40a, 50a, 60a Heat seal portion 20b, 60b First region 20c Second region 21, 41, 51, 61 Lithium ion battery 22, 42, 52, 62 Lithium ion Battery body 24, 44, 54, 64 Metal terminal (tab)
p Area where epoxy resin is applied n Area where epoxy resin is not applied

Claims (4)

A peripheral portion containing an electrochemical cell body including a positive electrode made of a positive electrode active material and a positive electrode current collector, a negative electrode made of a negative electrode active material and a negative electrode current collector, and an electrolyte filled between the positive electrode and the negative electrode It is used for the exterior body that seals and stores the electrochemical cell body inside by heat sealing,
A packaging material for an electrochemical cell configured by laminating at least a base material layer, a metal foil layer subjected to chemical conversion treatment on the surface, an acid-modified polyolefin layer, and a thermal adhesive resin layer,
A heat resistant resin coating layer is formed on the surface of the metal foil layer,
A packaging material for electrochemical cells, wherein the resin coating layer is formed excluding at least a part of a region to be heat sealed.   The packaging material for an electrochemical cell according to claim 1, wherein the resin coating layer is formed by printing and applying a heat resistant resin in a predetermined pattern on the surface of the metal foil layer.   The packaging material for an electrochemical cell according to claim 2, wherein the predetermined pattern is a dot pattern.   The packaging material for an electrochemical cell according to any one of claims 1 to 3, wherein the resin coating layer is made of a resin mainly composed of an epoxy resin.

Images