JP2000215863A - Battery case sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a case to store a battery such as a polymer battery, having an excellent barrier against vapor and other gas, mechanical strength such as puncture resistance, a stable structure against electrolyte, suitability to high temperatures and high moisture proof. SOLUTION: In this battery case sheet comprising a layered product having a heat seal layer 4 for the furthest inner layer forming a case to store components of a battery, forming the outside of the metal foil layer 1 of the layered product at least containing the metal foil layer 1 into an outer layer 2, and forming its inside into an inner layer 3, the outer layer 2 contains an oriented film of synthetic resin as a first base material 2a, the inner layer 3 contains an oriented film of synthetic resin as a second base material 3a, the second base material 3a is a nylon film of aromatic nylon resin or blended resin of aromatic nylon resin and aliphatic resin, the second base material layer is a film formed by using a resin obtained by blending **-** of straight chain aliphatic resin with 100 weight part of aromatic nylon resin, and the heat sheet layer 4 contains acid denatured polyorefine resin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a battery case sheet for accommodating constituent materials of a battery, and more particularly to a sheet which can be suitably used for a case of a sheet-shaped battery or the like.

[0002]

2. Description of the Related Art Heretofore, a metal case has been generally used as a case for storing constituent materials of a battery.
However, with the development and spread of various electronic devices such as notebook computers and mobile phones, their weight and thickness have been reduced, and the batteries used in them have been made as light as possible. In order to reduce the space for the battery in the equipment, the weight and thickness of the battery itself are required to be reduced. In order to meet such demands, for example, various sheet-shaped batteries which are made light and thin in a sheet shape by introducing a polymer material into an electrode or an electrolyte of the battery have been researched and developed. However, regarding the battery case used for these sheet batteries, in addition to its lightness and thinness, strength, water vapor and other gas barrier properties, heat resistance, durability, sealing properties, adhesion to electrode terminals, and the like are taken into consideration. For example, there is a case formed of a laminate in which a first base material, a metal foil layer, a second base material, and a heat seal layer are stacked in this order. An adhesive layer or an adhesive resin layer is formed between the respective layers. By using a sheet made of the laminated body as a battery case and storing battery constituent materials therein, the battery is protected from the occurrence of tears and pinholes caused by external friction or piercing, and the battery is stored. The battery is also protected from stabs and the like from inside the battery constituent material.

[0003]

Hitherto, in the construction of the laminate, biaxially stretched nylon has been used as the second base material. Biaxially stretched nylon is a tough film that is used to prevent the occurrence of pinholes due to piercing, which is required as a battery case. In addition, when the case is hermetically sealed, the heat seal of the electrode terminal portion tends to be thinner due to the heat and pressure of the heat seal, and the metal foil layer may come into contact with the electrode terminal. The presence of the second base material or the corresponding film ensures the insulation between the metal foil layer and the electrode terminal T without thinning the second base material layer even in the heat seal. However, conventionally, as the second base material, a film made of a linear nylon resin such as 6 nylon or 66 nylon has been used. However, it has been found that films made of these linear nylon resins have hygroscopicity, and in a moisture proof test, water tends to enter the case. The present invention is excellent in water vapor and other gas barrier properties,
In addition, it has a structure that is stable against mechanical strength or electrolyte, including piercing resistance, and has high temperature resistance,
Another object of the present invention is to provide a case for housing a battery such as a polymer battery made of a laminate having a high moisture-proof property.

[0004]

Means for Solving the Problems A heat seal layer is provided on the innermost layer forming a battery case for accommodating a constituent material of a battery, and an outer layer is provided outside the metal foil layer of the laminate including at least the metal foil layer, In the battery case sheet formed of a laminate having the inside as an inner layer, a stretched film made of a synthetic resin is used as a first base material for the outer layer, and a second base material is used for a second base material.
A battery case sheet including a stretched film made of a synthetic resin as a base material, wherein the second base material is a nylon film made of an aromatic nylon resin or a resin obtained by blending an aromatic nylon resin and an aliphatic resin. And
The second base material layer is based on 100 parts by weight of the aromatic nylon resin.
It is a film formed using a resin blended with 5 to 100 parts by weight of a linear aliphatic nylon, and the heat seal layer is an acid-modified polyolefin resin.

[0005]

FIG. 1 is a schematic sectional view showing the structure of an embodiment of a sheet for a battery case according to the present invention. FIG.
BRIEF DESCRIPTION OF THE DRAWINGS It is a figure explaining the structure of the Example of the battery using the sheet | seat for battery cases of this invention, (a) The perspective view which shows the external appearance of a battery,
FIG. 3B is a cross-sectional view taken along the line XX, and FIG. The battery using the battery case sheet in the present invention is a thin battery such as a polymer battery, and its appearance is shown in FIG.
As shown in FIG. 2, a battery constituent material is housed in a battery case, and a part of the electrode terminal T is projected outside the battery. The storage state of the battery constituent material is shown in FIG. As shown in the cross section, the battery case P includes an electromotive unit cell C and a part of the electrode terminal T extended from the cell, the electrode terminal T protruding outside the battery case, and the electrode in the battery case. The portion between the terminal T and the terminal T is closely adhered to the heat seal portion S when the battery case is formed. Since the electrode terminals T protrude to the outside of the case, a part of the electrode terminals T is thermally bonded to a heat seal resin at a heat seal portion S of the case in order to ensure that the battery case is sealed as a case. Accordingly, the resin forming the heat seal layer of the sheet is an electrode formed of a conductive material such as a copper foil or an aluminum foil, which is a material for forming the electrode terminal T, at the same time that the resin itself has a thermal adhesive property to each other. A resin having thermal adhesiveness is also used for the terminals.

Further, as shown in FIG. 1, the laminate of the battery case sheet includes a metal foil layer 1 for barrier properties, and the outside of the metal foil layer is used as an outer layer 2. When the inside of the layer is the inner layer 3, the outer layer first base material 2a,
The inner layer 3 is provided with a second base material 3a and the inner layer is provided with a heat seal layer. By adopting such a configuration, the metal layer of the intermediate layer imparts excellent water vapor and other gas barrier properties, and since the base material layers are laminated on both sides thereof,
Since the metal foil layer is protected and the occurrence of cracks and pinholes is prevented, good gas barrier properties are maintained.

Conventionally, a nylon film has been used as the second substrate 3a. As the second base material 2a, the nylon film prevents piercing of the projecting portion of the battery constituent material, and has excellent adhesion to the acid-modified polyolefin-based resin forming the heat seal layer, and generally forms a battery case. During the heat sealing, the heat sealing resin in the electrode terminal portion becomes thinner due to heat and pressure, and there is a risk of contact with the metal foil in the laminate of the battery case sheet. Due to its existence, it has been used as a base material for the inner layer for reasons such as preventing the danger of contact (the nylon film does not become thin).

However, when a battery case is actually made using such a laminated body having a material composition and a battery containing the battery constituent materials is stored at a constant temperature and humidity for a long period of time, water may enter the case. is there. After examining the cause in detail, as shown in FIG. 2 (c), the moisture in the nylon film used for the second base material 3a and in the layer of the heat seal portion from the end face of the battery case. And penetrates into the nylon layer in the direction of the arrow in the direction of the arrow.
It was confirmed that it would invade the water. Conventionally, as the second base material,
A film made of an aliphatic nylon such as 6, or 66 nylon was used. The film made of the aliphatic nylon has a hygroscopic property, and to be used as a battery case sheet, a film having a lower hygroscopic property, for example, a stretched film made of a polyester resin is considered. Nylon which can provide stable bonding strength in bonding has been used.

Accordingly, the present inventor has found, as a result of research, that aromatic nylon can be suitably used as a material having a necessary condition as the second base material and having low hygroscopicity. However, the layer composed only of the aromatic nylon has a possibility that the layer is hard and may cause stress cracks and the like, and as a countermeasure, the layer is made stable by blending the aromatic nylon resin with the linear aliphatic nylon resin. .

Further, the case is formed (bag-made) by heat bonding, and the innermost layer of the laminate is a heat seal layer.
The heat seal layer is formed of an acid-modified polyolefin resin that can be thermally bonded to the metal of the electrode terminal T.

The battery is used in a high temperature state,
It may also be left unattended. If the battery case does not have heat resistance, the heat seal portion may peel off in a high temperature state, and the electrolyte or the like may leak out. For example, it is required that an electronic device in which a battery is set be able to withstand even when left in a car. As a specific test standard for the heat resistance, it is required that the liquid does not leak after a lapse of 5 hours in an environment of 100 ° C. (called a dashboard test). In order to solve the above problem, as a result of researching various laminate structures and respective materials, as a laminate structure satisfying the conditions to be provided as a case for a polymer battery, by adopting the following material structure, The inventors have found that the above problems can be solved, and have completed the present invention.

The first base material layer is desirably used as a base material of the laminate, such as one having strength and good workability during production of a laminate such as printing and lamination.
In addition, various characteristics such as friction resistance are required for the surface layer of the battery. Further, not only the polymer battery but also a battery case requires various gas barrier properties including water vapor. In the present invention, a metal foil is used as the layer imparting the barrier property. In order to protect the barrier layer made of the metal foil and to reinforce the strength of the battery case, a second base material layer is provided inside the metal foil, and a heat seal layer is provided as the innermost layer. That is, the material composition of the present invention includes at least a base layer including a barrier layer made of a metal foil and a heat seal layer. Using an acid-modified polyolefin resin as the heat seal layer,
In addition, in order to comply with the dashboard test, the acid-modified polyolefin resin having a heat resistance of 100 ° C. or more is used. Examples of the method of laminating the respective layers include a dry lamination method, a sandwich lamination method in which an adhesive resin is extruded between layers to be bonded and pressure bonded, or a thermal lamination method in which a film made of a thermoadhesive resin is interposed and pressed. Etc. are available. Among these laminations, a sandwich lamination method by extruding an adhesive resin, a thermal lamination method with a film made of a heat-adhesive resin, and the like are preferable among the above-mentioned laminations from the viewpoint of resistance to an electrolytic solution.

Hereinafter, the case for a polymer battery of the present invention will be described in detail. In the present invention, in the configuration of the laminate, the lamination between the barrier layer and the inner layer does not include an adhesive layer of an organic solvent type, and the bonding between the layers is performed by a sandwich lamination method using an adhesive resin. Alternatively, a thermal adhesive sheet formed in advance may be laminated by a thermal laminating method with the thermal adhesive sheet interposed between the metal layer and the inner layer. As the heat laminate, a high-frequency welding method or a thermocompression bonding method can be used. The innermost layer is formed by extrusion-coating a thermo-adhesive resin. However, in the lamination outside the metal foil layer, the lamination may be performed by the dry lamination method. As described above, since the solvent-based adhesive layer is not provided in the lamination inside the metal foil layer, the electrolyte permeates the bonding interface, thereby dissolving the adhesive layer and delamination between the layers of the laminate. There is no danger of causing. Further, a plasma treatment may be applied to the inner layer or the surface of the heat-adhesive sheet laminated with the metal foil layer. Plasma treatment is performed by placing a rare gas in a vacuum chamber, a functional group gas obtained by passing a rare gas through a solution containing a functional group as a source gas, or a gas obtained by previously mixing a gas containing a functional group with a rare gas in the chamber. May be used to perform a plasma treatment on the treated surface of the film. In addition to the plasma processing in the vacuum chamber, a method of continuously performing atmospheric pressure glow discharge plasma processing on a film may be used.

Next, the individual layers forming the laminate of the polymer battery case sheet according to the present invention will be further described. As described above, the sheet for a battery case of the present invention uses a metal foil layer excellent in water vapor and other gas barrier properties in the middle, and has first and second bases excellent in various strengths and durability outside or inside thereof. Material layers are appropriately laminated, and a heat seal layer is further laminated on the innermost layer.

In the above configuration, an aluminum foil, a copper foil, or the like can be suitably used for the intermediate metal foil layer for providing gas barrier properties. Among them, aluminum foil is most preferably used because it is relatively inexpensive and has excellent workability such as bonding. An appropriate thickness of such a metal foil layer is 5 to 25 μm.

As the first substrate, for example, a biaxially stretched polyethylene terephthalate film (hereinafter, referred to as a biaxially stretched polyethylene terephthalate film)
PET film or PET), biaxially stretched nylon film (hereinafter, ON film or ON), polyethylene naphthalate film, polyimide film, polycarbonate film, etc. can be used, but processed with various performances including durability etc. Sex and economics,
PET film, ON film, etc. are particularly suitable. here
Comparing the characteristics of PET and ON, PET film is not particularly large difference, but PET film has low moisture absorption, excellent rigidity, scratch resistance, heat resistance, etc., ON has slightly high moisture absorption, but flexibility, piercing strength Excellent in bending strength, cold resistance, etc.
The thickness of the film used as such a substrate layer,
It is preferably from 5 to 100 μm, more preferably from 12 to 30 μm.
However, as the second base material, a film made of an aromatic nylon resin or a film formed from a resin obtained by blending an aromatic nylon resin and an aliphatic nylon resin is used for the above-described reason. The ratio of the blend of the aromatic nylon resin and the aliphatic nylon resin in the blend of the nylon constituting the second base film used as the battery case sheet of the present invention is 100 parts by weight of the aromatic nylon resin. 5 to 100 parts by weight of a straight-chain aliphatic nylon resin. When the proportion of the blend of the linear aliphatic nylon resin is 5 parts by weight or less, there is no effect of softening the film, and the proportion of the blend is 1%.
If the amount exceeds 00 parts by weight, there is a risk of moisture absorption into the battery case.

As described above, the innermost heat seal layer 4 has good heat adhesion to the metal of the electrode terminal T in addition to the heat adhesion between itself and the electrolyte, and In order to minimize the infiltration of water as much as possible, it is preferable that the material itself has low hygroscopicity or low water absorption.
Those which are stable without being swollen or eroded by the electrolytic solution are preferable.

Examples of the resin used for such a heat seal layer include ethylene-vinyl acetate copolymer, ethylene-acrylate copolymer, ethylene-methacrylate copolymer, and polyethylene or polypropylene. Polyolefin-based resins such as a blend of one or two or more copolymers can also be used, especially, acid-modified polyolefin-based resins, for example,
Ethylene-acrylic acid copolymer, polyolefin-based resin modified by copolymerizing acid components such as ethylene-methacrylic acid copolymer, or polyethylene, polypropylene, and their copolymers such as ethylene and propylene α-olefin copolymer, ethylene-vinyl acetate copolymer, ethylene-acrylate copolymer, ethylene-methacrylate copolymer, or polyolefin resin such as terpolymer of these Acrylic acid, methacrylic acid, maleic acid, maleic anhydride, citraconic anhydride, itaconic acid, unsaturated carboxylic acids such as itaconic anhydride, or a polyolefin resin modified by graft copolymerization of its anhydride is preferable. Used. And among these resins, the melting point is 10
By using a resin having a temperature of 0 ° C. or higher, the battery case has excellent heat resistance. If the melting point of the acid-modified polyolefin resin used for the heat seal layer is less than 100 ° C., when the battery is placed in a high temperature state, a peeling phenomenon may occur in the seal portion of the case, and the electrolyte may leak out.

The acid content of the acid-modified polyolefin resin is preferably in the range of 0.01 to 10% by weight. When the amount of the acid component is less than 0.01%, the heat adhesion to the metal is insufficient, and when the amount of the acid component exceeds 10% by weight, the film-forming properties are poor, which is not preferable. The thickness of such a heat seal layer is suitably in the range of 10 to 100 μm.

As a method of laminating each layer as described above,
In the present invention, as a laminating method inside the metal foil layer 1, an adhesive resin is bonded by a sandwich lamination method in which the resin is melt-extruded and pressure-bonded between two layers to be bonded. As the adhesive resin, the above-mentioned acid-modified polyolefin resin is used. In addition, the innermost heat seal layer is formed by directly melt-extrusion coating an acid-modified polyolefin-based resin on the second base material layer.
In forming the laminate of the battery case sheet according to the present invention, the acid-modified polyolefin-based resin is bonded to the inner layer of the metal foil layer 1 without using a dry lamination method using an organic adhesive. However, in the lamination outside the metal foil layer, a dry lamination method may be adopted.

[0021]

[Example 1]

PET12 / LMD / AL foil 15 / ADF40 / ON-A15 / HS50 PET: Biaxially stretched polyester film LMD: Dry lamination with polyurethane resin AL foil: Aluminum foil, ADF: Heat using film made of acid-modified polyolefin resin Bonding by lamination ON-A: Biaxially stretched nylon film (nylon resin is aromatic) The resin used is Novamid X21 (trade name, manufactured by Mitsubishi Engineering-Plastics Corporation) HS: Extrusion coating of acid-modified polyolefin resin [Example 2] PET12 / LMD / AL foil 15 / ADF40 / ON-A15 / HS50 ON-B: Biaxially stretched nylon film (nylon resin is a blend of 100 parts by weight of aromatic resin and 10 parts by weight of aliphatic resin) A laminate was prepared under the same conditions as in Example 1 except that the material was changed to ON-B. [Comparative Example 1] PET12 / LMD / AL15 / ADF40 / ON-C15 / HS50 ON-C: Biaxially stretched nylon film (nylon resin is aliphatic) Example except that the second substrate was ON-C A laminate was prepared under the same conditions as in Example 1. The same conditions as in Example 1 were used, except that the second base material was a film made of 6 nylon resin. <Storage test conditions> Ten pieces of each of the obtained batteries were placed in a constant temperature / humidity chamber at 40 ° C and 90% RH for each of Examples and Comparative Examples.
The performance of the battery was confirmed within a month. <Results> In both Examples 1 and 2, there were no abnormalities in the battery performance, but in Comparative Example 1, the performance was reduced in 3 out of 10 batteries. That is, by using an aromatic nylon or a film formed from a resin obtained by blending an aliphatic nylon resin with an aromatic nylon resin as the second base material, a material that is not likely to absorb moisture from the end face of the case. A sheet for a battery case could be obtained.

In the case of printing a character, a picture or the like on the surface of the battery case sheet having the structure shown in FIG.
By printing in advance on the inner surface (laminated surface) of the outer substrate of the first base material 2a by a so-called back-printing method, and laminating the next layer on this surface to complete the battery case sheet, the friction of the surface can be reduced. A printed image that is not damaged can be formed.

[0023]

As described in detail above, the battery case sheet of the present invention has at least four layers laminated in the order of the first base material layer, the metal foil layer, the second base material layer, and the heat seal layer. By forming the above-mentioned laminate and forming the second base material from an aromatic nylon resin or a nylon film formed from a blended resin of an aromatic nylon resin and an aliphatic nylon resin, light weight, thinness, and flexibility are achieved. Yes, and
In addition to various mechanical strengths and heat resistance, a sheet for a battery case having stable water vapor and other gas barrier properties in which moisture does not enter the battery case even after long-term storage can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a configuration of an embodiment of a battery case sheet of the present invention.

FIGS. 2A and 2B are diagrams illustrating the structure of an embodiment of a battery using the battery case sheet of the present invention. FIG. 2A is a perspective view showing the appearance of the battery, FIG. It is an enlarged view of a part.

[Explanation of symbols]

 D Battery T Electrode terminal C Cell P Case S Heat seal portion 1 Metal foil layer 2 Outer layer 2a First substrate 3 Inner layer 3a Second substrate 4 Heat seal layer 5 Adhesive layer

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Koji Shimizu 1-1-1 Ichigaya-Kaga-cho, Shinjuku-ku, Tokyo F-term in Dai Nippon Printing Co., Ltd. (reference) 4F100 AB01B AB10 AB33B AK01C AK01D AK03A AK41 AK47D AK48D AK51 AL07A BA04 BA07 BA10A BA10C BA13 EJ37C EJ37D EJ38 GB41 JD02 JJ03 JK01 JK13 JK17 JL03 JL12A YY00D 4J040 DA051 DA061 DA071 DA151 DA161 JA09 JB01 JB09 JB11 MA02 MB03 NA19 5H011 AA02 AH02 CCA CCH CC

Claims (3)

[Claims] 1. A heat-sealing layer is formed on an innermost layer forming a battery case accommodating a constituent material of a battery, and an outer layer is formed outside the metal foil layer of a laminate including at least a metal foil layer,
In the battery case sheet formed of a laminate having the inside as an inner layer, the outer layer includes a stretched film made of a synthetic resin as a first base material, and the inner layer includes a stretched film made of a synthetic resin as a second base material, A sheet for a battery case, wherein the second base material is a nylon film made of an aromatic nylon resin or a resin in which an aromatic nylon resin and an aliphatic resin are blended. 2. The method according to claim 1, wherein the second base material layer is made of an aromatic nylon resin.
The battery case sheet according to claim 1, wherein the film is a film formed using a resin in which 5 to 100 parts by weight of a linear aliphatic nylon is blended with respect to part by weight. 3. The battery case sheet according to claim 1, wherein the heat seal layer is an acid-modified polyolefin resin.