JP2013149558A - Packaging material for battery case and nonaqueous electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a packaging material for battery case which enhances the electrolyte resistance of a packaging material for battery case where a heat-resistant stretched resin layer, an adhesive layer, an aluminum layer, and a thermoplastic non-stretched resin layer are laminated.SOLUTION: The aluminum layer of a packaging material for battery case having a structure where a heat-resistant stretched resin layer, a first adhesive layer, an aluminum layer, and a thermoplastic non-stretched resin layer are laminated sequentially has a chromium layer or a chromium oxide layer formed at least on the thermoplastic non-stretched resin layer side surface. The chromium layer or a chromium oxide layer is preferably deposited by vacuum deposition.

Description

  The present invention relates to a battery case packaging material for manufacturing a battery case of a secondary battery such as a lithium ion secondary battery.

  Secondary batteries such as lithium-ion secondary batteries are widely used as power sources for various electronic devices such as mobile phones, smartphones, notebook computers, etc., but these secondary batteries have secondary battery elements as battery cases. It has an enclosed structure. Such a battery case is made by deep drawing or overhanging from a sheet-like packaging material for a battery case in which a heat-resistant stretched resin film, an aluminum foil, and a thermoplastic unstretched resin film are laminated via an adhesive. (Patent Document 1, Patent Document 2).

By the way, when it is going to apply the battery case formed from such a battery case packaging material to a lithium ion secondary battery, the battery case contains a fluorine-containing material such as LiPF ₆ or LiBF ₄ together with the secondary battery element. A nonaqueous electrolytic solution containing a lithium salt and a carbonate-based nonaqueous solvent such as ethylene carbonate or propylene carbonate is filled.

  In such a secondary battery, the halogen-containing lithium salt is hydrolyzed by moisture mixed in the electrolytic solution to generate a trace amount of hydrofluoric acid, and the aluminum foil is corroded. As a result, the aluminum foil and the thermoplastic unstretched resin layer There was a problem that delamination occurred. Therefore, in order to improve the electrolytic solution resistance of the battery case packaging material, it has been proposed to chromate the surface of the aluminum foil on the thermoplastic unstretched resin layer side by a wet process (Patent Document 3).

JP 2007-42469 A JP 2000-123800 A JP 2001-196036 A

  However, when the chromate treatment is performed by a wet process as in Patent Document 3, the chromate treatment liquid contains chromic acid and hydrogen fluoride. Therefore, the treatment line is corroded, adversely affects the human body, and the treatment cost of the treatment waste liquid. Problems such as increase occur.

  An object of the present invention is to solve the above-described problems of the conventional technology, and is a battery case packaging material in which a heat-resistant stretched resin film, an adhesive, an aluminum foil, and a thermoplastic unstretched resin film are laminated. It is an object to provide a packaging material for a battery case in which the resistance to electrolytic solution is improved without using a chromate treatment liquid containing chromic acid or hydrogen fluoride.

  In order to improve the electrolytic solution resistance of the battery case packaging material without using a chromate treatment solution containing chromic acid or hydrogen fluoride, the present inventor has used a dry process such as a vacuum deposition method. It has been found that a chromium layer or a chromium oxide layer may be formed on the surface of the aluminum layer, and the present invention has been completed.

  That is, the present invention provides a battery case packaging material having a structure in which a heat-resistant stretched resin layer, a first adhesive layer, an aluminum layer, and a thermoplastic non-stretched resin layer are sequentially laminated, and at least the thermoplastic non-stretched layer of the aluminum layer. Provided is a packaging material for a battery case, wherein a chromium layer or a chromium oxide layer is formed on a resin layer side surface by a dry process.

  The present invention also provides a secondary battery having a battery case formed by deep drawing or overhanging from the above battery case packaging material and a secondary battery element enclosed in the battery case.

  The packaging material for a battery case of the present invention having a structure in which a heat-resistant resin stretched layer, a first adhesive layer, an aluminum layer, and a thermoplastic resin non-stretched layer are sequentially laminated is at least the thermoplastic unstretched resin layer side of the aluminum layer. It has a structure in which a chromium layer or a chromium oxide layer is formed on the surface by a dry process. For this reason, the electrolytic solution resistance of the battery case packaging material can be improved without using a chromate treatment liquid containing chromic acid or hydrogen fluoride.

FIG. 1 is a cross-sectional view of the battery case packaging material of the present invention. FIG. 2 is a cross-sectional view of the battery case packaging material of the present invention. FIG. 3 is a cross-sectional view of the battery case packaging material of the present invention. FIG. 4 is a cross-sectional view of the battery case packaging material of the present invention.

As shown in FIG. 1, the battery case packaging material 10 of the present invention has a structure in which a heat-resistant stretched resin layer 1, a first adhesive layer 2, an aluminum layer 3, and a thermoplastic unstretched resin layer 4 are sequentially laminated. Alternatively, as shown in FIG. 2, it has a structure in which an aluminum layer 3 and a thermoplastic unstretched resin layer 4 are laminated with a second adhesive layer 5, and at least the thermoplastic unstretched resin layer of the aluminum layer 3. A chromium (Cr) layer or a chromium oxide (Cr ₂ O ₃ ) layer 3a is formed on the surface on the four side.

  In the present invention, the chromium layer or the chromium oxide layer 3a formed on the surface of the aluminum layer 3 on the side of the thermoplastic unstretched resin layer 4 is for improving the electrolytic solution resistance of the battery case packaging material. It is formed by a process. Here, among various metal layers and metal oxide layers, the reason for using a chromium layer or a chromium oxide layer is for a battery case even when the film is thin (for example, about 200 nm or less). This is because good resistance to electrolytic solution can be imparted to the packaging material.

  Examples of the dry process for forming such a chromium layer or chromium oxide layer 3a include a vacuum deposition method, a sputtering method, a PVD method such as an ion plating method, a CVD method such as a plasma polymerization method, and the like. Of these, vacuum deposition is preferred from the viewpoint of productivity.

  If the layer thickness of the chromium layer or the chromium oxide layer 3a is too thin, the electrolytic solution resistance is not sufficient, and if it is too thick, the moldability tends to decrease. Therefore, it is preferably 30 to 200 nm, more preferably 50 to 100 nm. is there.

1 and 2 are examples in which a chromium (Cr) layer or a chromium oxide (Cr ₂ O ₃ ) layer 3a is formed on the surface of the aluminum layer 3 on the thermoplastic unstretched resin layer 4 side. 3 and FIG. 4, a chromium (Cr) layer or a chromium oxide (Cr ₂ O ₃ ) layer 3 b may be further formed on the surface of the aluminum layer 3 on the heat resistant stretched resin layer 1 side. Thereby, the adhesiveness of the aluminum layer 3 and the heat resistant stretched resin layer 1 can be improved, and the occurrence of delamination can be suppressed.

Also, chromium (Cr) layer or a chromium oxide _(Cr 2 _{O 3)} layer 3b made of, thickness, forming method, etc., it may be similar to the chromium (Cr) layer or a chromium oxide _(Cr 2 _{O 3)} layer 3a it can.

  In addition, in this invention, it is preferable to apply the composite aluminum foil which laminated | stacked the chromium layer or the chromium oxide layer in advance on the aluminum foil for manufacture of the packaging material for battery cases of this invention.

  The heat-resistant stretched resin layer 1 constituting the battery case packaging material 10 of the present invention is a layer for protecting the battery case so that the aluminum layer is not exposed even in a high temperature environment and protecting the battery from a drop impact. . For this reason, the heat-resistant stretched resin layer 1 preferably has a glass transition temperature of 30 to 100 ° C., more preferably 40 to 90 ° C., and a softening point of 200 to 280 ° C., more preferably in consideration of processability. Is a resin having a heat resistance of 210 to 270 ° C., and has a breaking strength (JIS P8112) of preferably 150 to 350 MPa and an impact resistance (JIS K8134) of preferably 30000 to show good impact resistance. It is formed from 80000 J / m resin.

  Examples of the heat resistant stretched resin layer 1 include stretched polyamide films such as stretched nylon films, stretched polyimide films, stretched polyester films, and the like. Among these, from the viewpoint of strength and elongation, a stretched polyamide film, specifically, a stretched nylon film can be preferably used. Here, the stretching treatment is preferably biaxial stretching treatment, more preferably 4-axial stretching treatment.

  If the thickness of the heat-resistant stretched resin layer 1 is too thin, electronic performance tends to be impaired due to environmental temperature or drop impact, and if it is too thick, it tends to be difficult to form a sharp shape. It is 9-50 micrometers, More preferably, it is 15-30 micrometers.

  The first adhesive layer 2 constituting the battery case packaging material 10 of the present invention can be formed from a known adhesive, but when the battery case packaging material 10 is deep-drawn or stretched, In view of the fact that the heat-resistant stretched resin layer 1 that is the outer side of the battery case is stretched more strongly than the inner layer, thereby causing stress in the aluminum layer to cause cracks in the aluminum layer 3. In order to provide the first adhesive layer 2 with a role of relieving such stress, it may be formed from an adhesive mainly composed of a resin having a glass transition temperature of 0 to 30 ° C., preferably 3 to 15 ° C. preferable. By using a resin having such a glass transition temperature as a main component, the battery case packaging material 10 has practically no formability, in other words, an Erichsen value of 9 mm or more (according to JIS Z2247. At the same time, the peel strength between the heat-resistant stretched resin layer 1 and the aluminum layer 3 can be improved to at least 3 N / 15 mm (JIS K6854) or more. Moreover, since the softening point of the main component resin tends to lower the adhesion reliability at high temperature if it is too low, and tends to cause poor adhesion if it is too high, it is preferably 30 to 110 ° C., more preferably 40 ° C. or higher.

  As the main material of the first adhesive layer 2, it is preferable to use a polyester resin. This is because it has an advantage of excellent moldability as compared with other general adhesives (for example, urethane adhesives).

  If the weight average molecular weight of the polyester resin is too small, the adhesive strength tends to decrease. If the weight average molecular weight is too large, the solubility in a solvent tends to decrease. Moreover, since the hydroxyl value of the polyester resin tends to be difficult to proceed with crosslinking by the curing agent if it is too small, and tends to be hydrolyzed if it is too large, it is preferably 3 to 6, more preferably 4 to 5. is there. Further, if the softening point of the polyester resin is too low, the adhesion reliability at high temperature tends to be lowered, and if it is too high, adhesion failure tends to occur. Therefore, the softening point is preferably 30 to 110 ° C., more preferably 40 to 80. ° C. If the acid value of the polyester resin is too low, crosslinking by the curing agent tends to be difficult to proceed, and if it is too high, hydrolysis tends to occur, and thus it is preferably 1 to 5, more preferably 1 to 3.

  Examples of the diol component constituting the polyester resin include ethylene glycol, propylene glycol, 1,4-butanediol, neopentyl glycol, 1,6-hexylene glycol and the like. These can be used alone or as a mixture of two or more diol components. Examples of the dibasic acid component include terephthalic acid, isophthalic acid, adipic acid, sebacic acid and the like. These can also be used as a dibasic acid component individually or in mixture of 2 or more types.

  Adjustment of the glass transition temperature of the polyester resin composed of such components is performed by changing each kind of the diol component or the dibasic acid component or their ratio, changing the weight average molecular weight of the polyester resin, or the like. be able to. For example, when trying to lower the glass transition temperature, increase the amount of 1,4-butanediol used as the diol component, increase the amount of adipic acid used as the dibasic acid component, or the weight average molecular weight of the polyester resin For example. Conversely, when trying to raise the glass transition temperature, increase the amount of neopentyl glycol used as the diol component, increase the amount of terephthalic acid used as the dibasic acid component, or increase the weight average molecular weight of the polyester resin. For example.

  The first adhesive layer 2 may be composed only of a polyester resin exhibiting a glass transition temperature of 0 to 30 ° C., but a known tackifier, various rubbers, a crosslinking agent, a crosslinking accelerator, etc. It can contain in the range which does not impair an effect.

  If the thickness of the first adhesive layer 2 is too thin, the stress relaxation ability cannot be said to be sufficient, and if it is too thick, the volume energy density tends to decrease, so it is preferably 2 to 5 μm, more preferably 3 to 4 μm. is there.

  The aluminum layer 3 constituting the battery case packaging material 10 of the present invention is a layer that prevents water vapor and oxygen from entering the battery case and contributes to the shape retention of the battery case.

  Examples of the aluminum layer 3 include an aluminum foil formed by rolling, a composite aluminum sheet formed by vapor deposition on a resin film base such as polyester or polyimide. From the viewpoint of productivity and cost, an aluminum foil formed by rolling can be preferably used. In the present invention, “aluminum” includes not only pure aluminum but also various aluminum alloys.

  If the thickness of the aluminum layer 3 is too thin, pinholes that cannot be ignored tend to be generated or cracks are generated due to external forces, and if it is too thick, the moldability of the battery case packaging material 10 tends to decrease. Therefore, it is preferably 15 to 150 μm, more preferably 20 to 80 μm.

  The thermoplastic unstretched resin layer 4 constituting the battery case packaging material 10 of the present invention insulates the electronic element in the battery case from the aluminum layer 3 of the packaging material, and also provides a heat sealing property to the packaging material. It is.

  The reason why this thermoplastic unstretched resin layer 4 is thermoplastic is to maintain the airtightness of the battery case and exhibit heat sealability, and the reason that it is unstretched is to ensure sufficient heat sealability. That's why.

  If the glass transition temperature of the thermoplastic unstretched resin layer 4 is too low, the adhesive reliability at high temperatures tends to decrease, and if it is too high, the heat sealability tends to decrease. ° C, more preferably -20 to -15 ° C, and if the softening point is too low, the heat sealability tends to decrease, and if it is too high, the adhesion reliability at high temperatures tends to decrease. Preferably it is 130-180 degreeC, More preferably, it is 140-170 degreeC.

  Examples of the thermoplastic unstretched resin layer 4 include unstretched polyolefin films, such as polyethylene films, polypropylene films, polyethylene-polypropylene copolymer films, acids (such as maleic acid and acrylic acid), and esters (such as acrylics). An acid ester) -modified polypropylene film can be preferably mentioned. Among them, an unstretched polyolefin film is preferable, and a polypropylene film is particularly preferable.

  If the thickness of the thermoplastic unstretched resin layer 4 is too thin, sufficient heat seal strength cannot be obtained, and if it is too thick, the volume energy density tends to decrease, preferably 10 to 70 μm, more preferably 20 μm. ~ 50 μm.

  The battery case packaging material 10 of the present invention may be provided with a second adhesive layer 5 between the aluminum layer 3 and the thermoplastic unstretched resin layer 4 as shown in FIG. In this case, the second adhesive layer 5 may be formed of the same type of adhesive as the first adhesive layer 2, and other acrylic adhesives, ester adhesives, urethane adhesives, styrene / butadiene based adhesives. You may form from a thermoplastic elastomer adhesive agent etc. Among them, those formed from a styrene / butadiene-based thermoplastic elastomer adhesive are preferable from the viewpoint of resistance to electrolytic solution and waterproofness.

  If the thickness of the second adhesive layer 5 is too thin, sufficient adhesive strength cannot be obtained, and if it is too thick, the volume energy density tends to decrease. Therefore, the thickness is preferably 1 to 5 μm, more preferably 2 to 4 μm. is there.

In FIGS. 1 and 2, an example has been described in which thermoplastic unstretched resin layer 4 side surface of the chromium (Cr) layer or chromium oxide of the aluminum layer 3 (Cr 2 _{O 3)} layer 3a is formed, As shown in FIGS. 3 and 4, a chromium (Cr) layer or a chromium oxide (Cr ₂ O ₃ ) layer 3 b may be further formed on the heat resistant stretched resin layer 1 side surface of the aluminum layer 3. Thereby, the adhesiveness of the aluminum layer 3 and the heat resistant stretched resin layer 1 can be improved, and the occurrence of delamination can be suppressed.

  The battery case packaging material of the present invention can be manufactured using a known film forming method or lamination method. For example, in the battery case packaging material of FIG. 1, a first adhesive layer forming composition is applied to a heat-resistant stretched resin film and dried to form a first adhesive layer, and the first adhesive layer is formed on the first adhesive layer. After pasting the aluminum exposed surface of the aluminum foil on which the chromium layer or the chromium oxide layer has been laminated in advance, the thermoplastic unstretched resin layer is melted and extruded to the chromium layer or the chromium oxide layer of the aluminum foil It can manufacture by laminating. 2 is applied to the heat-resistant stretched resin film and dried to form a first adhesive layer, and the first adhesive layer is formed on the first adhesive layer. After pasting the aluminum exposed surface of the aluminum foil on which the chromium layer or the chromium oxide layer is laminated in advance, the chromium layer or the chromium oxide layer of the aluminum foil and the thermoplastic unstretched resin film disposed so as to face the aluminum layer In the meantime, it can be manufactured by laminating the composition for forming the second adhesive layer while melting and extruding.

  The packaging material for battery case of the present invention is excellent in electrolytic solution resistance without using a chromate treatment liquid containing chromic acid or hydrogen fluoride by a dry process on the surface of the thermoplastic unstretched resin layer side of the aluminum layer. A chromium layer or a chromium oxide layer is formed on the surface of the aluminum layer. Therefore, corrosion by the electrolytic solution does not occur in the aluminum layer, and delamination does not occur between the aluminum layer and the thermoplastic unstretched resin layer. Moreover, problems such as corrosion of the processing line, adverse effects on the human body, and increased cost of waste liquid treatment that occur when the chromate treatment liquid is used do not occur.

  Hereinafter, the packaging material for battery cases of the present invention will be described more specifically according to examples.

Reference example 1
An aluminum foil having a 100 nm thick chromium deposition layer formed on one side under a vacuum deposition condition in which a metal vacuum is heated by irradiating a laser beam with an output of 200 mA under a pressure of 10 ⁻⁴ Pa using a general vacuum deposition apparatus. It was created.

Reference example 2
Using a general vacuum deposition system, a chromium oxide deposition layer with a thickness of 100 nm is formed on one side under the vacuum deposition conditions of irradiating and heating metal chromium with a laser beam with a pressure of 10 ⁻⁴ Pa and an output of 200 mA in an oxygen atmosphere. An aluminum foil was made.

Reference example 3
An aluminum foil having a nickel vapor deposition layer with a thickness of 100 nm formed on one side under a vacuum vapor deposition condition in which metal nickel is irradiated with a laser beam with an output of 200 mA at a pressure of 10 ⁻⁴ Pa and heated using a general vacuum vapor deposition device. It was created.

Reference example 4
A 100 nm thick aluminum oxide vapor deposition layer is formed on one side under a vacuum vapor deposition condition in which a general vacuum vapor deposition system is used to heat metal aluminum by irradiating a laser beam with a pressure of 10 ⁻⁴ Pa and an output of 200 mA in an oxygen atmosphere. An aluminum foil was made.

Reference Example 5
A 100 nm thick silicon oxide vapor deposition layer is formed on one side under a vacuum vapor deposition condition in which a general vacuum vapor deposition system is used to heat metal silicon by irradiating a laser beam with a pressure of 10 ⁻⁴ Pa and an output of 200 mA in an oxygen atmosphere. An aluminum foil was made.

Reference Example 6
By immersing the aluminum foil in an electroless chromium plating solution (ALT-610, DIPSOL), an aluminum foil having a 100 nm thick silicon oxide vapor deposition layer formed on both surfaces of the aluminum foil was created.

Example 1
A toluene solution (polyester 15% by volume) of polyester resin (UE3500, Unitika Ltd.) was applied to one side of a 15 μm thick 4-axis stretched nylon film (ON, Unitika Ltd.) to a dry thickness of 3 μm. And dried to form a first adhesive layer, which was wound around a roll so that the first adhesive layer was inside.

  On the adhesive layer of the sheet unwound from the obtained roll, a 35 μm thick composite aluminum foil having a chromium layer formed on one side of Reference Example 1 was heated with a heat drum heated to 60 ° C. from the aluminum exposed surface side. Lamination was performed while applying a linear pressure of 3.0 kg / cm, and the film was wound on a roll. Next, the aluminum layer of the sheet unwound again from the wound roll is opposed to a separately prepared 30 μm-thick unstretched polypropylene film (GLC, Mitsui Chemicals, Inc.) from the chromium layer side. By applying a styrene / butadiene / styrene (SBS) adhesive (Tuftec M1913, Asahi Kasei Co., Ltd.) as a second adhesive layer between them to a layer thickness of 3 μm, and laminating by a dry lamination method A case packaging material was obtained.

Example 2
A battery case packaging material of Example 2 was produced by repeating the same operation as in Example 1 except that the composite aluminum foil of Reference Example 2 was used instead of the composite aluminum foil of Reference Example 1.

Comparative Example 1
Instead of the composite aluminum foil of Reference Example 1, a solid 35 μm thick aluminum foil (8021-o material, Sumi Light aluminum foil (No. The battery case packaging material of Comparative Example 1 was produced by repeating the same operation as in Example 1 except that the above was used.

Comparative Examples 2-5
In place of the composite aluminum foil of Reference Example 1, comparative examples 2, 3, 4, and 4 were repeated by repeating the same operations as in Example 1, except that the composite aluminum foils of Reference Examples 3, 4, 5, and 6 were used. 5 battery case packaging materials were produced.

<Evaluation of electrolyte resistance>
A battery case of 30 mm × 45 mm × 4 mm was prepared from the battery case packaging material of Example 1-2 and Comparative Example 1-5, and a 1 mol / L LiPF ₆ ethylene carbonate solution was charged therein, and a polypropylene cap And kept standing in an environment of 80 ° C. and 90% RH for 72 hours. After storage, the electrolyte solution was poured out, and the presence or absence of peeling of the thermoplastic unstretched resin layer in contact with the electrolyte solution was visually observed. As a result, it was found that the battery case packaging materials of Examples 1 and 2 were not peeled off and were excellent in electrolytic solution resistance. On the other hand, in the battery case packaging materials of Comparative Examples 1 to 5, peeling was observed, and it was found that the electrolytic solution resistance was poor.

  The packaging material for a battery case of the present invention is improved in its electrolytic solution resistance without using a chromate treatment solution containing chromic acid or hydrogen fluoride. Therefore, it is useful for a battery case of a lithium ion secondary battery.

DESCRIPTION OF SYMBOLS 1 Heat resistant stretched resin layer 2 1st adhesive layer 3 Aluminum layer 3a, 3b Chromium layer or chromium oxide layer 4 Thermoplastic unstretched resin layer 5 2nd adhesive layer 10 Packaging material for battery cases

Claims (9)

  In a battery case packaging material having a structure in which a heat-resistant stretched resin layer, a first adhesive layer, an aluminum layer, and a thermoplastic non-stretched resin layer are sequentially laminated, dry the aluminum layer at least on the surface of the thermoplastic unstretched resin layer side. A packaging material for a battery case, wherein a chromium layer or a chromium oxide layer is formed by a process.   The packaging material for battery cases according to claim 1, wherein a chromium layer or a chromium oxide layer is formed by a vacuum deposition method.   The packaging material for a battery case according to claim 1 or 2, wherein the chromium layer or the chromium oxide layer has a thickness of 30 to 200 nm.   The packaging material for battery cases according to claim 1 or 2, wherein the heat-resistant stretched resin layer is a stretched polyamide film, and the thermoplastic unstretched resin layer is an unstretched polyolefin film.   The battery case packaging material according to claim 4, wherein the stretched polyamide film is a stretched nylon film and the unstretched polyolefin film is a nonstretched polypropylene film.   The packaging material for battery cases according to any one of claims 1 to 5, wherein the aluminum layer and the thermoplastic unstretched resin layer are laminated by a second adhesive layer.   The battery case packaging material according to claim 6, wherein the second adhesive layer is formed from a styrene / butadiene-based thermoplastic elastomer adhesive.   A secondary battery comprising a battery case formed by deep drawing or overhanging from the battery case packaging material according to any one of claims 1 to 7, and a secondary battery element enclosed in the battery case.   The secondary battery according to claim 8, wherein the secondary battery element is a lithium ion secondary battery element.

Images