JP2005093315A - Packaging material for lithium ion battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a packaging material for a lithium ion battery having excellent cold formability, causing no whitening even if electrolyte solution sticks to the surface in a packaging process and causing no delamination between a metallic foil and a sealant layer even if the battery has been stored for a long period after packaging. <P>SOLUTION: In this packaging material, a basic material layer is composed of polyester films, in both longitudinal and lateral directions, having tensile fracture growth of ≥200%, tensile fracture strength of ≥200 Mpa and Young's modulus of ≤3.2 Gpa, a metallic film is a soft aluminum alloy foil containing iron by 0.7 to 1.7% and having an aluminum purity of ≥97.9% and with a boehmite treatment applied on at least an anchor coat layer side, the anchor coat layer is made of an isocyanate compound, and an adhesive resin layer is made of mixed resin of metallocene based straight chain polyethylene resin of 70 to 90 wt% with a density of ≥0.92 g/cm<SP>3</SP>and low-density polyethylene resin of 30 to 10 wt%. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a laminate having a multilayer structure in which a metal foil such as aluminum is laminated as a gas barrier material in the packaging field of industrial products and the like. Even when packaged, the present invention relates to a laminate in which the surface does not melt and deteriorate and does not undergo delamination under the influence of the contents.

In packaging materials such as pharmaceuticals and industrial products, an aluminum foil is mainly used as a gas barrier material, and a laminated material obtained by laminating this aluminum foil between a base film and a sealant layer is used. In recent years, electric and electronic devices have been reduced in size and thickness, and the batteries used in these devices are similarly required to be reduced in size and thickness. Instead of the battery, a battery of cold-molded type using a laminated material laminated in the configuration of biaxially stretched nylon film / polyurethane adhesive / aluminum foil / polyurethane adhesive / sealant layer has come into circulation. . However, when a lithium ion battery is packaged with the laminated material having the above-described structure, a strong permeable electrolyte containing LiPF ₆ passes through the sealant layer and stops on the surface of the barrier aluminum foil. Swelling caused a decrease in the laminate strength between the aluminum foil and the sealant layer, and finally there was a problem of delamination, resulting in leakage of the electrolyte. In order to improve the above problem, a laminate material is proposed in which a surface of an aluminum foil subjected to surface treatment for improving adhesion is used, and the foil is laminated between a biaxially stretched nylon film and a sealant layer. (For example, refer to Patent Document 1, Patent Document 2, and Patent Document 3.)
JP 2002-110112 A JP 2002-216715 A JP 2002-343314 A

  However, in the above configuration, the electrolyte solution adheres to the biaxially stretched nylon film used on the surface of the exterior material in the battery manufacturing process, etc., the biaxially stretched nylon film dissolves, the surface is whitened, and the product value is lost. There was a problem such as.

  The problem of the present invention is that it has excellent cold formability, the surface does not whiten even if the electrolyte solution adheres to the surface in the battery packaging process, and the metal foil and the sealant layer even when the battery is stored for a long time after packaging An object of the present invention is to provide a packaging material for a lithium ion battery in which no delamination occurs.

The invention according to claim 1 of the present invention is a laminate in which a metal foil, an anchor coat layer, an adhesive resin layer, and a sealant layer are sequentially laminated on one surface of a substrate layer. Both in the transverse direction, it is made of a polyester film having a tensile fracture elongation of 200% or more, a tensile fracture strength of 200 MPa or more, and a Young's modulus of 3.2 GPa or less. The metal foil contains 0.7 to 1.7% of iron and has an aluminum purity of 97. Metallocene linear polyethylene resin 70 to 90 having a soft aluminum alloy foil of 9% or more and at least the surface on the anchor coat layer side being subjected to boehmite treatment and the adhesive resin layer having a density of 0.92 g / cm ³ or more. An exterior material for a lithium ion battery comprising a mixed resin of 10% by weight and 30% by weight of a low-density polyethylene resin.

  The invention according to claim 2 of the present invention is the exterior material for a lithium ion battery according to the invention according to claim 1, wherein the anchor coat layer is made of an isocyanate compound.

The exterior material for a lithium ion battery of the present invention is a laminate in which a metal foil, an anchor coat layer, an adhesive resin layer, and a sealant layer are sequentially laminated on one surface of a substrate layer. Both in the transverse direction, it is made of a polyester film having a tensile fracture elongation of 200% or more, a tensile fracture strength of 200 MPa or more, and a Young's modulus of 3.2 GPa or less. The metal foil contains 0.7 to 1.7% of iron and has an aluminum purity of 97. .9% or more soft aluminum alloy foil and at least the surface of the anchor coat layer side is boehmite treated, the anchor coat layer is made of an isocyanate compound, and the adhesive resin layer has a density of 0.92 g / cm ³ or more. Since it is composed of a mixed resin of 70 to 90% by weight of a linear polyethylene resin and 30 to 10% by weight of a low density polyethylene resin, During excellent press formability, even when adhering electrolyte in an exterior material surface during battery packaging process is not to dissolve and whitening. Furthermore, delamination between the metal foil and the sealant layer does not occur even when stored for a long time after packaging a strong permeable organic electrolyte or the like as the contents. Therefore, the outer packaging material for lithium ion batteries of the present invention has sufficient chemical resistance as a laminated material for wrapping them, and other industrial products (for example, bactericides and prosthetics) containing strong permeable substances as contents. It can also be used as a packaging material.

  The exterior material for a lithium ion battery of the present invention will be described in detail below based on one embodiment. FIG. 1 is a side sectional view for explaining an embodiment of an outer packaging material for a lithium ion battery according to the present invention. In the thickness direction, a base material layer (1), an adhesive layer (2), and a metal foil (3). The anchor coat layer (4), the adhesive resin layer (5), and the sealant layer (6) are laminated.

  The base material layer (1) is made of polyester fiber having a tensile fracture elongation of 200% or more, a tensile fracture strength of 200 MPa or more, and a Young's modulus of 3.2 Gpa or less in both the longitudinal direction and the transverse direction. By using the film having the above numerical values, the moldability when the laminate is cold press-molded is excellent. The thickness is appropriately selected, but is preferably 25 μm. In addition, the said tensile fracture elongation and tensile fracture strength are the values measured by the method prescribed | regulated to JIS-C2318, and the Young's modulus is the value measured by the method prescribed | regulated to ASTM-D882.

As the adhesive layer (2), a two-component mixed adhesive in which a main component having a hydroxyl group and a curing agent having an isocyanate group are generally used is mainly used, and the main component is a polyester polyol, Polyether polyols are mainly used. As a coating method, it is applied by a gravure coating method, a roll coating method or the like. The application amount of the adhesive is 1 to 5 g / m ² (dry state).

  The metal foil (3) is a soft aluminum alloy foil having an iron content of 0.7 to 1.7% and an aluminum purity of 97.9% or more, and at least the surface on the anchor coat layer side is subjected to a boehmite treatment. Yes. By using the boehmite-treated soft aluminum alloy foil, it is excellent in cold press formability, it is difficult to generate cracks, pinholes, wrinkles, etc. of the soft aluminum alloy foil at the time of molding, and sharp molding with good shape retention is achieved. It becomes possible. A thickness in the range of 20 to 60 μm is used.

In the boehmite treatment applied to the metal foil (3), an additive such as ammonia or triethanolamine is added in distilled water in the range of 0.01 to 1.0% by weight, preferably in the range of 0.1 to 0.5% by weight. The treatment liquid added in step 1 is prepared, and the treatment liquid is heated in the range of 75 to 100 ° C., preferably in the range of 85 to 100 ° C., more preferably in the range of 90 to 100 ° C., and one side or both sides of the metal foil is 1 The metal foil which performed the boehmite process can be obtained by processing for more than minutes, Preferably it is 2 minutes or more, More preferably, it is 3 minutes or more. This processing may be performed by a web method using a coater or the like, or may be processed by a batch method.

  By performing this boehmite treatment, the surface of the metal foil has a needle-like structure, and a large amount of -OH groups can be present on the surface, and -O- groups and hydrogen on the resin surface of the layer laminated thereon The adhesion strength can be further improved by forming a bond.

  The anchor coat layer (4) is composed of an isocyanate compound, and the compounds used are 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, xylylene diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate. Various diisocyanate monomers such as 4,4-diphenylmethane diisonate, and polymers and derivatives thereof are used.

  In addition, when the application amount of these isocyanate compounds is the same as that of a conventional two-component curable urethane adhesive, a reaction between isocyanate groups (-NCO groups) occurs, and the bond is weak to solvents. There is a risk of forming. Therefore, the thickness applied to the boehmite-treated surface of the metal foil is preferably 3 μm or less, more preferably 1 μm or less.

  -NCO group in the isocyanate compound of the anchor coat layer (4) and -OH group generated during high temperature melting of the mixed resin of the adhesive resin layer (5) are bonded by urethane bonding to form a network structure. Adhesiveness is obtained and it has the effect | action which provides tolerance with respect to various organic electrolyte solution.

The adhesive resin layer (5) is composed of a mixed resin of 70 to 90% by weight of a metallocene linear polyethylene resin having a density of 0.92 g / cm ³ or more and 30 to 10% by weight of a low density polyethylene resin. Since the resin is extruded and laminated at a resin temperature of 300 ° C. or higher, oxidation is promoted at a high temperature to generate a polar group on the resin surface, improving the adhesive force and improving chemical resistance.

  The sealant layer (6) is composed of a single layer or multilayer polyolefin film. A thickness of 35 to 100 μm is used.

  The outer packaging material for lithium ion batteries of the present invention will be described below according to specific examples. The present invention is not limited to these examples.

As the base material layer (1), a polyester film having a thickness of 25 μm having a tensile fracture elongation of 220%, a tensile fracture strength of 210 MPa, and a Young's modulus of 2.9 GPa in both the longitudinal and transverse directions (Teijin Limited) 4g / m ² of polyurethane adhesive (Toyo Morton Co., Ltd., trade name: AD502) as the adhesive layer (2) using a dry laminating machine on one side of the film. (Dry state) After coating and drying, as a metal foil (3), the surface of the foil was treated with 95 ° C. warm water containing 0.5% by weight of ethanolamine for 3 minutes using a separate coater in advance, and a boehmite-treated thickness of 40 μm A soft aluminum alloy foil of alloy number 8021 is bonded by a known method. Subsequently, a tolylene diisocyanate compound (Toyo Morton Co., Ltd., trade name: CAT-10) solution having a solid content of 5% by weight as an anchor coat layer (4) was applied to the boehmite-treated surface of the soft aluminum alloy foil with a thickness of 0. It is applied and dried by a gravure method so as to be 3 μm (dry state), and further, 90 wt% of a metallocene linear polyethylene resin having a density of 0.933 g / cm ³ as an adhesive resin layer (5) on the coated surface. And density 0.91
A mixed resin with 10% by weight of 9 g / cm ³ low density polyethylene resin is extruded at a resin temperature of 330 ° C. to a thickness of 20 μm, laminated, and then used as a sealant layer (6) as a metallocene linear low density polyethylene. Adhesive resin layer (5) with a polyolefin resin two-layer film having a thickness of 35 μm composed of a mixed resin obtained by mixing 40% by weight of a random copolymer polypropylene resin with 60% by weight of the resin layer and a random copolymer polypropylene resin. Then, the outer packaging material for a lithium ion battery of the present invention was prepared.

  In Example 1, as a base material layer (1), a polyester film having a thickness of 25 μm having a tensile fracture elongation of 200%, a tensile fracture strength of 200 MPa, and a Young's modulus of 3.1 GPa in both the longitudinal and lateral directions ( Using Toray Industries, Inc., trade name: QR-01), as a metal foil (3), the foil was surface-treated with 95 ° C. warm water containing 0.5% by weight of ethanolamine for 3 minutes in advance with another coater machine, A packaging material for a lithium ion battery of the present invention was prepared in the same manner except that a 40 μm thick soft aluminum alloy foil having an alloy number of 8079 was used.

  Below, the comparative example of this invention is demonstrated.

  As a base material layer, a nylon film having a thickness of 25 μm having a tensile fracture elongation of 150%, a tensile fracture strength of 200 MPa, and a Young's modulus of 2.5 GPa in both the longitudinal and transverse directions (Kojin Co., Ltd., trade name) : A comparative lithium ion battery exterior material was prepared in the same manner as in Example 1 except that Bonyl RX) was used.

  As a base material layer, a polyester film (Toyobo Co., Ltd., trade name: 25 μm thick) having a tensile fracture elongation of 130%, a tensile fracture strength of 230 MPa, and a Young's modulus of 4.5 GPa in both the longitudinal and transverse directions. A comparative lithium ion battery exterior material was prepared in the same manner as in Example 2 except that E5100) was used.

<Comparison result>
Using the packaging materials for lithium ion batteries of Examples 1 and 2 of the present invention and the packaging materials for comparative lithium ion batteries of Examples 3 to 4, the moldability and electrolyte resistance were evaluated by the following test methods, Compared. The results are shown in Table 1.
(1) Formability test Using the exterior materials of Examples 1 to 4, cold press molding was performed with male and female molds having a length of 50 mm, a width of 35 mm, a depth of 4 mm, and a corner R section of 1.5. The quality of the sex was evaluated.
(2) Electrolytic drop test The electrolytic solution of ethylene carbonate / ethylene methyl carbonate = 1/1 + LiPF ₆ (1.5N) was dropped on the surface of the exterior material of Examples 1 to 4, and the appearance of the surface dissolution and whitening was observed. Inspected.

From the results of Table 1, the exterior materials of the present invention of Examples 1 and 2 have good moldability during molding, and there is no dissolution or whitening of the exterior material surface, while the comparative exterior material of Example 3 is a surface. Was dissolved and whitened, and the packaging material for comparison in Example 4 had poor moldability.

It is a sectional side view explaining one embodiment of the exterior material for lithium ion batteries of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Base material layer 2 ... Adhesive layer 3 ... Metal foil 4 ... Anchor coat layer 5 ... Adhesive resin layer 6 ... Sealant layer

Claims (2)

In a laminate in which a metal foil, an anchor coat layer, an adhesive resin layer, and a sealant layer are sequentially laminated on one surface of the base material layer, the base material layer has a tensile fracture elongation of 200% or more in both the vertical and horizontal directions. It is a soft aluminum alloy foil made of a polyester film having a tensile fracture strength of 200 MPa or more and a Young's modulus of 3.2 GPa or less, and a metal foil having a contained iron content of 0.7 to 1.7% and an aluminum purity of 97.9% or more. In addition, at least the surface on the anchor coat layer side is subjected to boehmite treatment, and the adhesive resin layer has a density of 0.92 g / cm ³ or more of metallocene linear polyethylene resin 70 to 90% by weight and low density polyethylene resin 30 to 10% by weight. %, A lithium-ion battery exterior material.   The exterior material for a lithium ion battery according to claim 1, wherein the anchor coat layer is made of an isocyanate compound.