JP2019212534A - Exterior package material for secondary battery and production method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exterior material for a secondary battery capable of suppressing a decrease in adhesiveness between an aluminum foil layer and a sealant layer even when used in a state of being in contact with an electrolytic solution, and a method for producing the same. An exterior material for a secondary battery includes a sealant layer, an aluminum foil layer, and an adhesive layer sandwiched between the sealant layer and the aluminum foil layer. The aluminum foil layer has a hydrate film layer on the surface of the adhesive layer side. The hydrate film layer is (a) a dense first layer containing aluminum as a main component, and (b) a porous layer that is located closer to the adhesive layer than the first layer and contains magnesium and aluminum. And a second layer of. The first layer and the second layer each have a thickness of 500 to 1000 nm. The mass ratio of aluminum to magnesium in the second layer is 0.6 to 1.4. [Selection diagram] Figure 1

Description

  The present disclosure relates to a packaging material for a secondary battery and a method for manufacturing the same.

The secondary battery has a structure in which a positive electrode material, a negative electrode material, and an electrolytic solution are enclosed in a secondary battery exterior material. The electrolytic solution is a solution in which an electrolyte is dissolved in an aprotic solvent. Examples of the electrolyte include LiPF ₆ and LiBF ₄ . Examples of the aprotic solvent include propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate. Aprotic solvents have high penetrating power. 2. Description of the Related Art As a secondary battery exterior material, a laminate in which a sealant layer is laminated on the surface of an aluminum foil layer is known (see Patent Document 1).

JP 2002-144479 A

  When using an exterior material for a secondary battery in which a sealant layer is laminated on the surface of the aluminum foil layer, the electrolytic solution may penetrate into the gap between the aluminum foil layer and the sealant layer. In this case, the adhesion between the aluminum foil layer and the sealant layer is lowered. When the adhesiveness between the aluminum foil layer and the sealant layer decreases, the electrolyte solution easily leaks.

Moreover, water may permeate into the gap between the aluminum foil layer and the sealant layer from the end face of the secondary battery exterior material. The electrolytes LiPF ₆ and LiBF ₄ and water cause a hydrolysis reaction to generate hydrofluoric acid. The hydrofluoric acid corrodes the aluminum foil layer and further reduces the adhesion between the aluminum foil layer and the sealant layer.

  One aspect of the present disclosure is to provide a secondary battery exterior material and a method for manufacturing the same that can suppress a decrease in adhesion between the aluminum foil layer and the sealant layer even when used in a state of being in contact with an electrolytic solution. And

  One aspect of the present disclosure is an exterior material for a secondary battery including a sealant layer, an aluminum foil layer, and an adhesive layer sandwiched between the sealant layer and the aluminum foil layer. The aluminum foil layer includes a hydrate film layer on the surface of the adhesive layer. The hydrate film layer includes (a) a dense first layer mainly composed of aluminum, and (b) a porous layer that is located closer to the adhesive layer than the first layer and contains magnesium and aluminum. And a second layer. Each of the first layer and the second layer has a thickness of 500 to 1000 nm. The mass ratio of aluminum to magnesium in the second layer is 0.6 to 1.4.

Even if it uses the exterior material for secondary batteries which is one aspect of this indication in the state which contacts electrolyte solution, it is hard to fall the adhesiveness of an aluminum foil layer and a sealant layer.
Another aspect of the present disclosure is a method for manufacturing a packaging material for a secondary battery including a sealant layer, an aluminum foil layer, and an adhesive layer sandwiched between the sealant layer and the aluminum foil layer. In the method for manufacturing a secondary battery exterior material according to another aspect of the present disclosure, magnesium chloride having a concentration of 5.0 to 11.0 g / L and sodium bicarbonate having a concentration of 0.2 to 0.6 g / L And a hot water denaturation treatment on the aluminum foil layer using a mixed solution having a concentration of 1.0 to 5.0 g / L and a temperature of 75 ° C. or higher in the aluminum foil layer. A hydrate film layer is formed on the surface of the adhesive layer.

  According to the method for manufacturing a secondary battery exterior material according to another aspect of the present disclosure, even when the secondary battery is used in contact with the electrolytic solution, the secondary battery in which the adhesion between the aluminum foil layer and the sealant layer is not easily lowered. Can be manufactured.

It is a sectional side view showing the composition of packaging material 1 for secondary batteries. 3 is a side cross-sectional view illustrating a configuration of a secondary battery exterior material 101. FIG.

Exemplary embodiments of the present disclosure will be described with reference to the drawings.
1. Configuration of Secondary Battery Exterior Material (1-1) Layer Configuration of Secondary Battery Exterior Material For example, as shown in FIG. 1, the secondary battery exterior material 1 includes a sealant layer 3, an aluminum foil layer 5, And an adhesive layer 7. The adhesive layer 7 is sandwiched between the sealant layer 3 and the aluminum foil layer 5.

  The aluminum foil layer 5 includes a hydrate film layer 9 on the surface of the adhesive layer 7 side. The hydrate film layer 9 includes (a) a dense first layer 11 mainly composed of aluminum, and (b) a porous layer that is located closer to the adhesive layer 7 than the first layer 11 and contains magnesium and aluminum. A second layer 13 of quality.

  Further, for example, as shown in FIG. 2, the secondary battery exterior material 101 may include hydrate film layers 9 and 15 on both sides of the aluminum foil layer 5. The hydrate film layer 9 includes (a) a dense first layer 11 mainly composed of aluminum, and (b) a porous layer that is located closer to the adhesive layer 7 than the first layer 11 and contains magnesium and aluminum. A second layer 13 of quality.

  Further, the hydrate film layer 15 is located on the side of the base layer 19 (to be described later) with respect to (c) the dense first layer 12 mainly composed of aluminum and (d) the first layer 12, and magnesium. And a porous second layer 14 containing aluminum.

  The secondary battery exterior material 101 has a structure in which a hydrate film layer 9, an adhesive layer 7, and a sealant layer 3 are laminated in this order. Further, the secondary battery exterior material 101 has a structure in which a hydrate film layer 15, a base material layer adhesive layer 17, and a base material layer 19 are laminated in this order.

(1-2) Sealant layer The sealant layer has, for example, a function of improving the sealing performance against the electrolytic solution and a function of suppressing water vapor transmission from the cross-sectional direction of the secondary battery exterior material.

  The material of the sealant layer can be appropriately selected. The sealant layer includes, for example, a polyolefin film. The polyolefin-based film preferably includes an acid-modified polyolefin film. The acid-modified polyolefin film is a film containing acid-modified polyolefin. The acid-modified polyolefin is obtained by adding a dicarboxylic acid to a side chain of polyethylene or polypropylene. Examples of the acid-modified polyolefin include those obtained by adding maleic acid or maleic anhydride to a side chain of polypropylene.

  The sealant layer may be a film having a single layer structure or a film having a laminated structure in which a plurality of films are laminated. Examples of the laminated film include a two-layer film, a three-layer film, and a four-layer film. A film having a laminated structure can be produced, for example, by laminating a plurality of films by coextrusion.

  Examples of the laminated film include those obtained by laminating an acid-modified polyolefin film and another polyolefin film. Examples of the other polyolefin film include a polyamide film and a polyester film.

  As will be described later, the adhesive layer can contain an acid-modified polyolefin. When the adhesive layer contains an acid-modified polyolefin, the sealant layer preferably contains the same acid-modified polyolefin. For example, when the adhesive layer contains maleic anhydride-modified polypropylene, the sealant layer preferably also contains maleic anhydride-modified polypropylene.

  The sealant layer can be attached by, for example, a known laminating method. Examples of the laminating method include the following methods. A sealant layer and an adhesive layer are laminated. When the sealant layer contains an acid-modified polyolefin film, the sealant layer is disposed so that the acid-modified polyolefin film comes into contact with the adhesive layer. When a surface activation treatment surface is applied to one side of the sealant layer, the sealant layer is disposed so that the surface activation treatment surface comes into contact with the adhesive layer.

Next, the sealant layer and the adhesive layer are pressure-bonded while being heated to about 160 to 240 ° C., for example. The pressure for pressure bonding is, for example, 0.5 to ² kg / cm ² . The crimping time is, for example, about 0.5 to 3 seconds.

The thickness of the sealant layer is not particularly limited. The thickness of the sealant layer is preferably 5 μm or more, and more preferably 10 to 100 μm. When the thickness of the sealant layer is 5 μm or more, the sealant layer can be prevented from melting when the sealant layer is laminated. Thereby, it can suppress that a defect generate | occur | produces in a sealant layer. When the thickness of the sealant layer is 100 μm or less, the adhesive layer is easily melted when the sealant layer is laminated. Thereby, the adhesion of the sealant layer is improved.
(1-3) Aluminum foil layer An aluminum foil layer has a function which suppresses that moisture, gas, oxygen, etc. penetrate | invade into the inside of a secondary battery, for example. Moreover, an aluminum foil layer has a function which ensures the moldability and rigidity of the exterior material for secondary batteries, for example.

  The aluminum foil layer is made of aluminum foil. As a material of the aluminum foil layer, an aluminum alloy foil is preferable, and a soft aluminum foil is more preferable. Aluminum alloy foil has high tensile strength and elongation. The aluminum foil layer can be produced by a known method.

The tensile strength of the aluminum foil layer is preferably 90 MPa or more. The elongation of the aluminum foil layer is preferably 20% or more in the 0 ° direction.
The aluminum foil layer preferably contains iron as a part of the alloy component. The iron content in the aluminum foil layer is, for example, 0.6 to 2.0 mass%, preferably 1.2 to 1.6 mass%. When the aluminum foil layer contains iron, the spreadability of the aluminum foil layer is good. Moreover, when an aluminum foil layer contains iron, even if the exterior material for secondary batteries is bent, a pinhole hardly occurs in the aluminum foil layer. Moreover, when an aluminum foil layer contains iron, a side wall can be easily formed when shape | molding the embossing-type exterior material for secondary batteries.

  When the iron content in the aluminum foil layer is 0.6 mass or more, the above effect becomes more remarkable. When the iron content in the aluminum foil layer is 2.0% by mass or less, the flexibility of the aluminum foil layer is high. For this reason, for example, workability when forming a laminated battery pouch for a secondary battery exterior material is improved.

  The aluminum foil layer preferably contains silicon as a part of the alloy component. The silicon content in the aluminum foil layer is, for example, 0.05 to 0.9 mass%, preferably 0.06 to 0.09 mass%. When the content of silicon in the aluminum foil layer is 0.9% by mass or less, workability when the secondary battery exterior material is formed into a bag shape is improved. When the silicon content in the aluminum foil layer is 0.05% by mass or more, the strength and elongation of the secondary battery exterior material are increased. Therefore, workability when forming the secondary battery exterior material into a bag shape is improved.

  The thickness of the aluminum foil layer is preferably 9 to 200 μm, and more preferably 15 to 100 μm. When the thickness of the aluminum foil layer is 9 μm or more, the aluminum foil layer is hardly broken during press molding. Moreover, when the thickness of the aluminum foil layer is 9 μm or more, pinholes or the like are hardly generated in the aluminum foil layer. Therefore, permeation of oxygen and moisture can be suppressed by the aluminum foil layer. When the thickness of the aluminum foil layer is 200 μm or less, the weight and manufacturing cost of the secondary battery exterior material can be reduced.

For example, the aluminum foil layer may be a tempered aluminum alloy. Examples of the tempering treatment include solution treatment and aging treatment.
(1-4) Adhesive layer The adhesive layer adheres the sealant layer and the aluminum foil layer. By providing the secondary battery exterior material with an adhesive layer, the sealant layer can be attached to the aluminum foil layer even when the sealant layer itself does not have adhesiveness.

  The adhesive layer can be formed using, for example, an organosol. The organosol includes, for example, an organic liquid and a colloidal solid content dispersed in the organic liquid. Examples of the organic liquid include hydrocarbon liquids. Examples of the hydrocarbon-based liquid include toluene. Examples of the solid content include acid-modified polyolefin. The solid content concentration in the organosol is preferably in the range of 5 to 50% by mass.

  For example, an adhesive layer can be formed using organosol as follows. An organosol is applied to the surface of the hydrate film layer, and then a drying process is performed. A drying process is performed for 5 to 40 seconds under the temperature of 150-220 degreeC, for example. By this drying step, the organosol is solidified to form an adhesive layer. When the organosol contains acid-modified polyolefin as a solid content, the acid-modified polyolefin is uniformly distributed in the formed adhesive layer.

(1-5) Hydrate film layer The hydrate film layer is formed, for example, by subjecting an aluminum foil layer to a hot water denaturation treatment. The hydrate film layer includes a first layer and a second layer. The hydrate film layer may be composed of the first layer and the second layer, or may further include another layer.

  The 2nd layer with which the hydrate membrane | film | coat layer 9 in FIG.1 and FIG.2 is provided is located in the adhesive layer side rather than a 1st layer. The hydrate film layer 9 in FIGS. 1 and 2 has a function of improving the adhesion between the sealant layer and the aluminum foil layer and a function of improving the electrolytic solution resistance. The electrolytic solution resistance is a characteristic in which the adhesion between the aluminum foil layer and the sealant layer is hardly lowered even when used in a state where it is in contact with the electrolytic solution.

  The 2nd layer with which the hydrate film | membrane layer 15 in FIG. 2 is located is located in the base material layer side rather than the 1st layer. The hydrate film layer 15 in FIG. 2 has a function of improving the adhesion between the base material layer and the aluminum foil layer.

  The first layer is a dense layer mainly composed of aluminum. The first layer may be a layer made of aluminum, or may be a layer containing a smaller amount of other components than aluminum.

  The dense means a high-density structure that is not a hollow structure or a structure having pores. The thickness of the first layer is 500 to 1000 nm. When the thickness of the first layer is 500 nm or more, the corrosion resistance of the aluminum foil layer is further improved. When the thickness of the first layer is 1000 nm or less, the hydrate film layer is not easily destroyed, and the adhesion of the hydrate film layer to the aluminum foil layer is further improved. The measuring method of the thickness of the first layer is the measuring method described in Examples described later.

  The second layer is a porous layer containing magnesium and aluminum. The second layer may be a layer made of magnesium and aluminum, or may be a layer containing other components.

  The thickness of the second layer is 500 to 1000 nm. The measuring method of the thickness of the second layer is the measuring method described in Examples described later. When the thickness of the second layer is 500 nm or more, the corrosion resistance of the aluminum foil layer is further improved. Moreover, the adhesive agent which comprises an adhesive layer is fully contained in the void | hole of a 2nd layer because the thickness of a 2nd layer is 500 nm or more. As a result, the adhesion of the adhesive layer to the aluminum foil layer is further improved. When the thickness of the second layer is 1000 nm or less, the second layer is not easily broken, and the adhesion of the hydrate film layer to the aluminum foil layer is further improved.

The mass of magnesium contained in the second layer is Wm. Wa represents the mass of aluminum contained in the second layer. The mass ratio R of aluminum to magnesium in the second layer is Wa / Wm. The measuring method of mass ratio R is the measuring method described in the Example mentioned later. The mass ratio R is 0.6 to 1.4.
When the mass ratio R is 0.6 or more, the corrosion resistance of the hydrate film layer is further improved. Moreover, when the mass ratio R is 0.6 or more, the hydrate film layer is hardly brittle and the adhesion of the hydrate film layer to the aluminum foil layer is further improved. When the mass ratio R is 1.4 or less, the corrosion resistance of the secondary battery exterior material is further improved.

(1-6) Base material layer The base material layer has a function of protecting the aluminum foil layer, a piercing property and a heat resistance. Examples of the material for the base material layer include film stretched polyester and nylon film. Examples of the polyester resin constituting the stretched polyester film include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, copolymer polyester, and polycarbonate. Examples of nylon constituting the nylon film include nylon 6, nylon 6,6, a copolymer of nylon 6 and nylon 6,6, nylon 6,10, polymetaxylylene adipamide (MXD6), and the like.

  When the secondary battery packaging material is used as a packaging material for a lithium ion secondary battery, the base material layer preferably has insulating properties. The base material layer may be a film having a single layer structure or may be a film having a laminated structure in which a plurality of films are laminated. When the base material layer is a film having a laminated structure, pinhole resistance and insulation can be further enhanced.

  When the base material layer is a film having a laminated structure, it is preferable to include two or more resin layers. When the base material layer is a film having a laminated structure, the thickness of each layer is preferably 6 μm or more, and the thickness of each layer is more preferably 12 to 25 μm. When the thickness of each layer is 6 μm or more, the barrier property of the base material layer against water vapor and other gases is higher. Moreover, when the thickness of each layer is 6 μm or more, the piercing resistance of the base material layer against external pressure is further increased. When the thickness of each layer is 25 μm or less, the thickness of the entire secondary battery exterior material, the weight of the secondary battery exterior material, and the manufacturing cost of the secondary battery exterior material can be reduced.

  The base material layer can be bonded to the hydrate film layer 15 in FIG. 2 by, for example, a dry lamination method, a thermal lamination method, or the like. When the thermal lamination method is used, coextrusion, extrusion coating, or anchor coating agent can be used.

(1-7) Adhesive Layer for Base Layer For example, when the base layer is adhered to the hydrate film layer 15 in FIG. 2 by a dry lamination method, the adhesive layer for base layer can be used.

  The adhesive layer for the base material layer includes, for example, an adhesive containing an epoxy-containing urethane resin, a two-component curable urethane adhesive, a polyether urethane adhesive, a polyester adhesive, a polyester polyol adhesive, and a polyester polyurethane polyol adhesive. It can be formed using an adhesive or the like.

  Although the thickness of the adhesive layer for base material layers is not specifically limited, It is preferable that it is 1-10 micrometers, and it is more preferable that it is 3-7 micrometers. When the thickness of the adhesive layer for base material layers is 1 micrometer or more, the adhesive layer for base material layers tends to follow the surface unevenness | corrugation of a to-be-coated layer. Thereby, unevenness hardly occurs in the adhesion between the base material layer and the coated layer. As a result, poor adhesion between the base material layer and the coated layer can be suppressed. When the thickness of the base layer adhesive layer is 10 μm or less, the time required for drying the base layer adhesive layer can be reduced. Moreover, when the thickness of the adhesive layer for base material layers is 10 micrometers or less, it can suppress that the excess adhesive layer for base material layers protrudes from the edge part of the exterior material for secondary batteries. In addition, when the thickness of the adhesive layer for the base material layer is 10 μm or less, the thickness of the entire packaging material for the secondary battery, the weight of the packaging material for the secondary battery, and the manufacturing cost of the packaging material for the secondary battery are reduced. it can.

2. Method for Manufacturing Secondary Battery Exterior Material (2-1) Pretreatment The aluminum foil layer can be subjected to, for example, a pretreatment prior to the hot water modification treatment described later. The pretreatment is not particularly limited, and examples thereof include a pretreatment for removing oil and fat adhering to the surface of the aluminum foil layer and a pretreatment for removing a heterogeneous oxide film on the surface of the aluminum foil layer.

  As the pretreatment, for example, there is a method of first performing a degreasing treatment with a weak alkaline degreasing solution, then performing an alkali etching with a sodium hydroxide aqueous solution, and then performing a desmut treatment in a nitric acid or sulfuric acid aqueous solution. As another pretreatment, first, a method of performing a degreasing treatment and then performing an acid cleaning can be mentioned.

(2-2) Thermal denaturation treatment A hydrate film layer can be formed by subjecting the aluminum foil layer to a hot water denaturation treatment. In the hot water denaturation treatment, for example, an aluminum foil layer is immersed in the mixed solution. The mixed solution used for the hot water denaturation treatment includes magnesium chloride, sodium hydrogen carbonate, and sodium sulfate. Magnesium chloride contributes to the formation of the second layer. The solute in the mixed solution may be only the above three kinds, or may further contain other solutes. The solvent in the mixed solution is, for example, water. As the water, for example, industrial water, tap water, ground water, deionized water, distilled water and the like can be used.

It is preferable that the mixed solution is substantially free of sodium chloride. When a mixed solution does not contain sodium chloride substantially, it can suppress that pitting corrosion generate | occur | produces in an aluminum foil layer.
When the mixed solution contains magnesium chloride, a hydrate film layer containing magnesium oxide is formed on the surface of the aluminum foil layer after the hot water denaturation treatment. The hydrate film layer containing magnesium oxide is a denser layer than the hydrate film layer not containing magnesium oxide. Therefore, the corrosion resistance of the hydrate film layer containing magnesium oxide is high.

  In the mixed solution, sodium bicarbonate is ionized to generate carbonate ions. In the mixing solution, sodium sulfate is ionized to generate sulfate ions. Carbonate ions and sulfate ions suppress pitting corrosion in the aluminum foil layer. The reason will be described below.

  First, the mechanism of pitting corrosion will be described. A natural oxide film is present on the surface of the aluminum foil layer. The natural oxide film contains aluminum oxide. When chlorine ions are present in the mixed solution, the chlorine ions are adsorbed on the natural oxide film and react with the aluminum oxide contained in the natural oxide film to produce aluminum chloride. Since aluminum chloride is soluble in water, it elutes into the mixture. As a result, the active aluminum previously covered with the natural oxide film is exposed in the aluminum foil layer. This phenomenon is pitting corrosion.

  Carbonate ions and sulfate ions in the mixed solution are adsorbed to the natural oxide film in preference to chlorine ions. Therefore, the chlorine ions in the mixed solution are difficult to adsorb on the natural oxide film. As a result, carbonate ions and sulfate ions in the mixed solution can suppress pitting corrosion in the aluminum foil layer.

  The concentration of magnesium chloride in the mixed solution is 5.0 to 11.0 g / L. When the concentration of magnesium chloride in the mixed solution is 5.0 g / L or more, a hydrate film layer having a sufficient thickness can be formed. As a result, the corrosion resistance of the secondary battery exterior material is further improved, and the adhesion between the aluminum foil layer and the adhesive layer is further improved.

  When the concentration of magnesium chloride in the mixed solution is 11.0 g / L or less, the corrosion resistance of the secondary battery exterior material is further improved, and the adhesion between the aluminum foil layer and the coating film layer is further improved. The reason is that when the concentration of magnesium chloride in the mixed solution is 11.0 g / L or less, the mass ratio R in the second layer is hardly reduced.

  The pH in the mixed solution can be, for example, 9.2 to 11.0. The pH in the mixed solution can be adjusted, for example, by adding a sodium hydroxide solution or the like. When pH in a liquid mixture is 9.2 or more, the effect of magnesium chloride is accelerated | stimulated and the formation rate of a hydrate film | membrane layer increases. When pH in a liquid mixture is 11.0 or less, the melt | dissolution rate of aluminum does not rise easily. Therefore, a sufficient hydrate film layer having a sufficient thickness can be formed. As a result, the corrosion resistance of the secondary battery exterior material is further improved.

  The concentration of sodium bicarbonate in the mixed solution is 0.2 to 0.6 g / L. Sodium bicarbonate contributes to the formation of the second layer. When the concentration of sodium bicarbonate is 0.2 g / L or more, the effect of forming the second layer is further improved, and a hydrate film layer having a sufficient thickness can be formed. As a result, the corrosion resistance of the secondary battery exterior material is further improved, and the adhesion between the aluminum foil layer and the adhesive layer is further improved.

  When the concentration of sodium bicarbonate is 0.6 g / L or less, the surface of the aluminum foil layer is difficult to be coated with carbonate, and the elution of aluminum is difficult to be inhibited. Therefore, the growth of the hydrate film layer is hardly inhibited. As a result, the corrosion resistance of the secondary battery exterior material is further improved, and the adhesion between the aluminum foil layer and the adhesive layer is further improved.

  The concentration of sodium sulfate in the mixed solution is 1.0 to 5.0 g / L. Sodium sulfate contributes to growth of the hydrate film layer and contributes to an increase in the aluminum concentration in the hydrate film layer. When the concentration of sodium sulfate is 1.0 g / L or more, the above-described effect of sodium sulfate is further enhanced. When the concentration of sodium sulfate is 5.0 g / L or less, the mass ratio R in the second layer is unlikely to be excessive. As a result, the corrosion resistance of the secondary battery exterior material is further improved.

  When performing the hydrothermal modification treatment, the higher the temperature of the mixed solution, the faster the formation rate of the hydrate film layer and the thicker the hydrate film layer. The temperature of the mixed solution is preferably 75 ° C. or higher, more preferably 90 ° C. or higher, and particularly preferably 95 ° C. or higher.

  When the temperature of the mixed solution is 75 ° C. or higher, the hydrate film layer can be made thicker. As a result, the corrosion resistance of the secondary battery exterior material is further improved, and the adhesion between the aluminum foil layer and the adhesive layer is further improved.

  The treatment time for the hot water denaturation treatment is not particularly limited, but the longer the time, the thicker the hydrate film layer can be formed. The treatment time can be, for example, 5 to 60 minutes. When the treatment time is within this range, the hydrate film layer can be made sufficiently thick.

  After the hydrothermal modification treatment, for example, steam heating treatment may be performed on the aluminum foil layer. The steam heat treatment contributes to further formation of the hydrate film layer. The steam heat treatment particularly contributes to the further formation of the first layer. For example, the first layer can be made thicker by steam heat treatment, and the thickness of the first layer can be 500 to 1000 nm.

  According to the heat denaturation treatment described above, a hydrate film layer can be formed without necessarily using a substance that leads to environmental pollution. That is, according to the heat denaturation process mentioned above, the burden on the environment can be reduced.

  Moreover, according to the heat denaturation process mentioned above, a hydrate film layer can be formed without necessarily using a power source or the like. Therefore, according to the heat denaturation process mentioned above, the manufacturing cost of the exterior material for secondary batteries can be reduced.

(2-3) Surface activation treatment For example, a surface activation treatment can be performed on the sealant layer. By performing the surface activation treatment on the sealant layer, the adhesion of the sealant layer is improved. Further, the surface activation treatment can be performed on the base material layer. By performing the surface activation treatment on the base material layer, the adhesion of the base material layer is improved. In addition, the surface activation treatment can be performed on the adhesive layer. By performing the surface activation treatment on the adhesive layer, the adhesion of the sealant layer is improved.

  Examples of the surface activation treatment include corona treatment, ozone treatment, low temperature plasma treatment, glow discharge treatment, and oxidation treatment. In the low temperature plasma treatment, for example, oxygen gas, nitrogen gas, or the like can be used. In the oxidation treatment, for example, chemicals can be used.

  When the corona treatment is performed, the outermost molecular chain in the sealant layer or the base material layer can be cut to generate polar groups such as hydroxyl groups and carbonyl groups. Thereby, the adhesion of the sealant layer or the base material layer is improved.

3. Examples Hereinafter, the present disclosure will be specifically described by way of examples. However, the present examples are merely examples and do not limit the present disclosure.

(3-1) Production of Secondary Battery Exterior Material Secondary battery exterior materials of Examples 1 to 21 and Comparative Examples 1 to 16 were produced as follows.

(i) Formation of Hydrate Film Layer First, an aluminum foil layer having a thickness of 40 μm was prepared. The aluminum foil layer is made of an 8000 series alloy. The following pretreatment was performed on the aluminum foil layer. The degreasing agent was diluted with water to prepare an alkaline degreasing solution having a concentration of 2% by mass. The degreasing agent is Surf Cleaner 420N2 (trade name) manufactured by Nippon Paint Surf Chemicals. The above aluminum foil layer was immersed in an alkaline degreasing solution at 60 ° C. for 10 seconds to be alkaline degreased and washed with water.

Next, the aluminum foil layer was immersed in a dilute sulfuric acid aqueous solution for 5 seconds for acid treatment, and further washed with water. The concentration of the dilute sulfuric acid aqueous solution is 0.3%. The temperature of the dilute sulfuric acid aqueous solution is 50 ° C.
Next, the hot water modification process was performed with respect to the aluminum foil layer. The hot water denaturing treatment is a treatment of immersing the aluminum foil layer in a mixed solution containing magnesium chloride, sodium hydrogen carbonate, and sodium sulfate. By the hydrothermal modification treatment, a hydrate film layer was formed on the surface of the aluminum foil layer.

  Table 1 shows the conditions of the hot water denaturation treatment in each example and each comparative example. The conditions for the hydrothermal denaturation treatment include the composition of the mixed solution, the temperature of the mixed solution, and the treatment time. “Processing temperature” in Table 1 means the temperature of the mixed solution.

(Ii) Measurement of thickness of hydrate film layer The thickness of the hydrate film layer formed in each Example and each Comparative Example was measured as follows. First, the aluminum foil layer on which the hydrate film layer was formed was cut using an ultramicrotome to prepare a thin sample having a thickness of about 100 nm. The cutting direction is parallel to the plate thickness direction of the aluminum foil. Next, the thin piece sample was observed by TEM. The thickness of the first layer was measured at arbitrary 10 points in the observation visual field, and the average value thereof was taken as the thickness of the first layer. The size of the observation field is 1 μm × 1 μm. Further, the thickness of the second layer was measured at arbitrary 10 points in the observation visual field, and the average value thereof was taken as the thickness of the second layer. Table 1 shows the measurement results of the thickness of the hydrate film layer.

Further, the morphology of the first layer and the second layer was observed during TEМ observation, and it was confirmed that the first layer was a dense layer, and that the second layer was a porous layer.
(iii) Measurement of Mass Ratio R For each example and each comparative example, the mass ratio R was measured as follows. First, glow discharge emission spectroscopic analysis was performed on the aluminum foil layer, and the relationship between the depth from the surface of the aluminum foil layer and the spectrum intensity of aluminum was obtained. Moreover, the relationship between the depth from the surface of an aluminum foil layer and the intensity | strength of the spectrum of magnesium was acquired.

  Next, the spectrum of aluminum was integrated from the surface of the aluminum foil layer to a depth corresponding to the thickness of the second layer. Further, the magnesium spectrum was integrated from the surface of the aluminum foil layer to a depth corresponding to the thickness of the second layer. The thickness of the second layer is a value obtained by TEM observation. A value obtained by dividing the value obtained by integrating the aluminum spectrum by the value obtained by integrating the magnesium spectrum was defined as a mass ratio R. The calculated mass ratio R is shown in Table 1 above.

(iv) Formation of adhesive layer An adhesive composed of a modified polyolefin was uniformly applied to the surface of the hydrate film layer with a bar coater. Next, dry baking was performed at a temperature of 200 ° C. for 20 seconds to form an adhesive layer. The basis weight of the adhesive layer is 1.0 ± 0.5 g / m ² . Next, the adhesive layer was subjected to corona treatment. Corona treatment corresponds to surface activation treatment.

  A CPP film having a thickness of 60 μm was prepared. This CPP film corresponds to the sealant layer. One side of the CPP film was subjected to corona treatment. Corona treatment corresponds to surface activation treatment. Next, a CPP film and an adhesive layer were laminated. At this time, the CPP film was disposed so that the corona-treated surface of the surface of the CPP film was in contact with the adhesive layer. Next, hot melt lamination was performed under conditions of a temperature of 110 ° C. and 1 m / min. The secondary battery exterior material was completed through the above steps.

(3-2) Evaluation of Exterior Material for Secondary Battery For each of the examples and the comparative examples, the characteristics of the exterior material for the secondary battery were evaluated by the following tests (i) to (iii).

(I) Evaluation of heat seal strength A rectangular test piece was cut out from a secondary battery exterior material. The test piece has a long side length of 100 mm and a short side length of 50 mm. Next, the test piece was folded in two at the fold lines passing through the midpoints of the two long sides. At this time, the test piece was folded in half so that the CPP film was inside. Next, among the test pieces folded in half, a portion having a width of 15 mm located in the vicinity of the folding line was heat-sealed. A heat sealer manufactured by Yasuda Seiki Seisakusho was used for heat sealing. The conditions for heat sealing were as follows.

Temperature: 180 ° C
Pressure: 2.4 kg / G pressure Heat sealing time: 2 sec
Next, using a tensile tester, both ends in the long side direction of the test piece were pulled in opposite directions to measure the heat seal strength of the heat sealed portion. The measurement conditions for the seal strength were as follows.

Distance between chucks: 50mm
Peeling speed: 50mm / min
Peel angle: 180 °
The heat seal strength was evaluated according to the following criteria. In addition, this reference | standard is based on the JAS specification value (Agriculture and Forestry Standard Article 10) of the sealing strength of a retort pouch. ○ means pass and × means fail. The evaluation results are shown in Tables 2 and 3.

○: Heat seal strength is 15.3 N / cm or more.
X: Heat seal strength is less than 15.3 N / cm.

(Ii) Peeling mode evaluation After the evaluation of the heat seal strength, the peeled surface of the used test piece was visually observed. The peeled surface is a surface of the test piece that has been heat-sealed and then peeled off. Based on the visual observation results, the peeling mode was evaluated according to the following criteria. ○ means pass and × means fail. The evaluation results are shown in Table 2 and Table 3.

A: Cohesive failure occurred at the interface between CPP films.
X: Peeling occurred at the interface between the adhesive layer and the aluminum foil layer.
(Iii) Evaluation of Electrolytic Solution Properties Two rectangular test pieces were cut out from the secondary battery exterior material. The sizes of the test pieces are 90 mm long and 50 mm wide, respectively. Two test pieces were overlapped so that the CPP film was inside. Next, end portions of the test pieces were heat-sealed on three sides among the four sides of the overlapped test pieces. The heat seal was performed in a range of a width of 5 mm. The conditions for heat sealing were as follows.

Temperature: 200 ° C
Pressure: 2kg / cm ²
Heat sealing time: 1 sec
As a result, a rectangular bag having one side opened and three sides heat-sealed was formed. In a glove box having a dew point of −80 ° C. or lower, 0.27 ml of electrolyte was injected into the bag from the opening side of the bag. The electrolytic solution contains LiPF ₆ at a concentration of 1 mol / L. The solvent of the electrolytic solution is a solvent in which EC and EMC are mixed so that the volume ratio is 3: 7.

  Next, the open side of the bag was heat sealed under the same conditions as when 3 sides were heat sealed. As a result, the inside of the bag was sealed with the electrolyte contained in the bag. The bag was held at 85 ° C. for a predetermined period. The period for holding the bag was 1 day, 3 days, and 7 days. After the holding period, the bag was disassembled and washed with pure water, and the appearance of the test piece constituting the bag was observed. The resistance to electrolytic solution of the test piece was evaluated according to the following criteria. ○ means pass and × means fail.

○: Even when the bag was held for 7 days, there was no peeling between the CPP film and the aluminum foil layer.
X: When a bag is held for 7 days, there is peeling of the CPP film and the aluminum foil layer.
(iv) Evaluation result When all of the evaluation results of the heat seal strength, the peeling mode, and the electrolytic solution resistance were “◯”, the comprehensive evaluation result was “◯”. In other cases, the result of comprehensive evaluation was “x”. The results of comprehensive evaluation are shown in Table 2 and Table 3 above.

  As shown in Table 2, in Examples 1 to 21, the overall evaluation was “◯”. On the other hand, as shown in Table 3, in Comparative Examples 1 and 2, the evaluation results of the heat seal strength, the peeling mode, and the resistance to electrolytic solution were “x”. This is presumably because the thickness of the second layer became insufficient because the concentration of magnesium chloride in the mixed solution used for the hot water denaturation treatment was low.

  In Comparative Example 3, the evaluation results of the heat seal strength, the peeling mode, and the resistance to electrolytic solution were “x”. This is presumably because the mass ratio R became excessively low because the concentration of magnesium chloride in the mixed solution used for the hot water denaturation treatment was high.

  In Comparative Example 4, the evaluation results of the heat seal strength, the peeling mode, and the resistance to electrolytic solution were “x”. This is presumably because the thickness of the second layer became insufficient because the concentration of sodium bicarbonate in the mixed solution used for the hot water denaturation treatment was low.

  In Comparative Example 5, the evaluation results of the heat seal strength, the peeling mode, and the electrolytic solution resistance were “x”. In Comparative Example 6, the evaluation result of the heat seal strength was “x”. This is presumed to be because the hydrate film layer was not sufficiently formed because the concentration of sodium bicarbonate in the mixed solution used for the hot water denaturation treatment was high.

  In Comparative Examples 7 and 8, the evaluation result of the heat seal strength was “x”. This is presumably because the mass ratio R in the second layer was excessively high because the concentration of sodium sulfate in the mixed solution used for the hot water denaturation treatment was low.

  In Comparative Examples 9 and 10, the evaluation results of the heat seal strength, the peeling mode, and the electrolytic solution resistance were “x”. This is presumably because the mass ratio R in the second layer was excessively low because the concentration of sodium sulfate in the mixed solution used for the hot water denaturation treatment was high.

  In Comparative Examples 11 and 12, the evaluation results of the heat seal strength, the peeling mode, and the electrolytic solution resistance were “x”. This is presumably because the thickness of the first layer became insufficient because the temperature of the mixed solution used for the hot water denaturation treatment was low.

  In Comparative Example 13, the evaluation result of the heat seal strength was “x”. This is presumably because the concentration of sodium hydrogen carbonate in the mixed solution used for the hot water denaturation treatment was high, the time for the hot water denaturation treatment was too long, and the thickness of the second layer was excessively increased.

  In Comparative Example 14, the evaluation result of the heat seal strength was “x”. This is presumably because the concentration of magnesium chloride in the mixed solution used for the hot water denaturation treatment was high, the time for the hot water denaturation treatment was too long, and the thickness of the second layer was excessively increased.

In Comparative Example 15, the evaluation result of the heat seal strength was “x”. This is presumably because the hot water denaturation treatment time was too long and the thickness of the first layer became excessively large.
In Comparative Example 16, the evaluation result of the heat seal strength was “x”. This is presumably because the concentration of sodium hydrogen carbonate in the mixed solution used for the hot water denaturation treatment was low, the hot water denaturation treatment time was too long, and the thickness of the first layer became excessively large.

4). Other Embodiments Although the embodiment of the present disclosure has been described above, the present disclosure is not limited to the above-described embodiment, and various modifications can be made.

(1) The base material layer may be laminated on the sealant layer.
(2) A function of one component in each of the above embodiments may be shared by a plurality of components, or a function of a plurality of components may be exhibited by one component. Moreover, you may abbreviate | omit a part of structure of each said embodiment. In addition, at least a part of the configuration of each of the above embodiments may be added to or replaced with the configuration of the other above embodiments. In addition, all the aspects included in the technical idea specified from the wording described in the claims are embodiments of the present disclosure.

  (3) In addition to the secondary battery exterior material described above, the present disclosure is realized in various forms such as a product including the secondary battery exterior material as a constituent element, a secondary battery, and a secondary battery manufacturing method. You can also.

DESCRIPTION OF SYMBOLS 1,101 ... Exterior material for secondary batteries, 3 ... Sealant layer, 5 ... Aluminum foil layer, 7 ... Adhesive layer, 9, 15 ... Hydrate film layer, 11, 12 ... First layer, 13, 14 ... First 2 layers, 17 ... adhesive layer for base material layer, 19 ... base material layer

Claims (3)

A secondary battery exterior material,
A sealant layer,
An aluminum foil layer;
An adhesive layer sandwiched between the sealant layer and the aluminum foil layer;
With
The aluminum foil layer comprises a hydrate film layer on the surface of the adhesive layer side,
The hydrate film layer includes (a) a dense first layer mainly composed of aluminum, and (b) a porous layer that is located closer to the adhesive layer than the first layer and contains magnesium and aluminum. And a second layer of
The thicknesses of the first layer and the second layer are 500 to 1000 nm,
The secondary battery exterior material in which the mass ratio of aluminum to magnesium in the second layer is 0.6 to 1.4. A method for producing an exterior material for a secondary battery comprising a sealant layer, an aluminum foil layer, and an adhesive layer sandwiched between the sealant layer and the aluminum foil layer,
Magnesium chloride having a concentration of 5.0 to 11.0 g / L, sodium bicarbonate having a concentration of 0.2 to 0.6 g / L, and sodium sulfate having a concentration of 1.0 to 5.0 g / L A secondary battery that forms a hydrate film layer on the surface of the aluminum foil layer on the side of the adhesive layer by subjecting the aluminum foil layer to a hot water denaturation treatment using a mixed solution having a temperature of 75 ° C. or higher. Method of manufacturing exterior materials. It is a manufacturing method of the exterior material for secondary batteries according to claim 2,
The hydrate film layer includes (a) a dense first layer mainly composed of aluminum, and (b) a porous layer that is located closer to the adhesive layer than the first layer and contains magnesium and aluminum. And a second layer of
The thicknesses of the first layer and the second layer are 500 to 1000 nm,
The manufacturing method of the exterior material for secondary batteries whose mass ratio of aluminum with respect to magnesium in the said 2nd layer is 0.6-1.4.