JP2004327048A - Sheet for polymer battery case - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sheet used in a case housing a polymer battery with high barrier properties against gas such as steam or others, high mechanical strength including piercing resistance, usable even at high temperature, and stable against an electrolyte. <P>SOLUTION: The sheet for the battery case houses constitution materials of the battery on the inside, used for forming the battery, and is constituted with a laminate comprising a first substrate layer/a metal foil layer/an adhesive resin layer/a second substrate layer/a thermal adhesion resin layer. The laminate is laminated by sandwich lamination or an extrusion coating process of the second substrate and the thermal adhesion resin, and the adhesive resin layer and/or the thermal adhesion resin layer comprise/comprises acid modified polyolefin, and the acid modified polyolefin has a melting point of 100°C or higher. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
TECHNICAL FIELD The present invention relates to a battery case sheet for storing constituent materials of a battery, and more particularly to a sheet that can be suitably used for a case of a sheet-shaped battery or the like.
[0002]
[Prior art]
Conventionally, in most cases, a metal case has been 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 these devices have also been made as light as possible. Lightening and thinning of the battery itself are required to reduce the space for the battery in the device.
[0003]
In order to meet such demands, for example, various sheet-shaped batteries in which a polymer material is introduced into an electrode or an electrolyte of the battery and which is light and thin in a sheet shape or the like have been researched and developed. However, the battery case used for these sheet batteries is not only light and thin, but also has strength, water vapor and other gas barrier properties, heat resistance, durability, sealing properties, adhesiveness to electrode terminals, etc. What was satisfactory was not completed.
[0004]
[Problems to be solved by the invention]
The present invention has been made in view of such a background, the object thereof is light and thin, and its strength, heat resistance, durability, as well as water vapor and other gas barrier properties, sealing properties, An object of the present invention is to provide a battery case sheet excellent in performance and workability, such as adhesiveness to an electrode terminal, and suitable for use in a lightweight and thin battery case with high productivity.
Conventionally, a laminate made of a base film, a barrier material, and a thermo-adhesive resin has been used to form a case of a polymer battery. In some cases, delamination may occur.
Further, a modified polyethylene such as ethylene methacrylic acid or the like is used as the thermal adhesive resin of the innermost layer of the conventional battery case laminate. However, severe conditions (for example, in a high temperature state) when the battery is used are used. Use, etc.).
The present invention, as a sheet used in a case for accommodating a polymer battery, is excellent in gas barrier properties such as water vapor and the like, and has mechanical strength such as puncture resistance and the like, and can be used even at a high temperature. This also provides a stable configuration.
[0005]
[Means for Solving the Problems]
A battery case sheet for containing a battery constituent material therein and forming a battery, comprising: a first base layer / metal foil layer / adhesive resin layer / second base layer / heat A laminate formed of a laminate having an adhesive resin layer configuration, wherein the metal foil layer and the second base layer, and the second base layer and the thermoadhesive resin are laminated by sandwich lamination or extrusion coating. A sheet for a polymer battery case, wherein the adhesive resin layer and / or the heat adhesive resin layer is made of an acid-modified polyolefin resin, wherein the acid-modified polyolefin resin has a melting point of 100 ° C. or more. Including.
[0006]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 is a schematic sectional view showing the configuration of an embodiment of the battery case sheet of the present invention. FIG. 2 is a schematic sectional view showing the configuration of another embodiment of the battery case sheet of the present invention. FIGS. 3A and 3B are a perspective view and a sectional view taken along line XX, respectively, showing the polymer battery of the present invention.
As shown in FIG. 3, the polymer battery of the present invention is a battery in which a battery body of an electrode terminal T extended from a cell C is hermetically packaged by a case P. Since the electrode terminals T protrude to the outside of the case, a part thereof is adhered to the case inner surface resin at the seal portion of the case.
The battery case sheet of the above configuration is overlapped so that the heat-adhesive resin layers thereof are in contact with each other, and heat-sealed the peripheral edge to form a bag-shaped battery case having one end opened. In addition to containing the battery constituent materials such as electrodes and electrolytes, the electrode terminals are extended from the inside to the outside of the case, and the openings are heated between the heat-adhesive resins of the sheet and between the heat-adhesive resin layer and the electrode terminals. The battery is formed by heat bonding with a seal and sealing.
Accordingly, in the heat-adhesive resin layer of the sheet, the electrode terminals formed of a conductive material such as a copper foil or an aluminum foil, which is a material for forming the electrode terminals T, at the same time as having the heat adhesion to each other. Also, a resin having thermal adhesiveness is used.
[0007]
Further, in the polymer battery case sheet, the laminate is formed of a metal foil layer and a heat-adhesive resin layer for an outer base material layer and a barrier property. In order to prevent the occurrence of pinholes and breakage due to piercing, second and third base layers are further formed between the metal foil layer and the heat-adhesive resin layer. By adopting such a configuration, the metal foil layer of the intermediate layer imparts excellent water vapor and other gas barrier properties, and the base material layer or the heat-adhesive resin layer is laminated on both sides thereof. Since the foil layer is protected and the occurrence of cracks and pinholes is prevented, good gas barrier properties are maintained.
The base material layer laminated on the outside or inside of the metal foil layer protects the metal foil layer as described above, and at the same time, improves the strength and other performances of the sheet and various resistances. The adhesive resin layer imparts heat sealability to the sheet.
Further, at least the first base material layer or the second base material layer is laminated on both sides of the metal foil layer, and since these are all non-conductive materials, the battery case sheet is non-conductive. Acts as a conductive sheet.
[0008]
Further, as a result of various studies, as a layer configuration of the laminate used for the battery case, the surface side as the case was used as the first base material layer, the barrier layer was laminated, and By laminating the two base layers, the barrier layer was sandwiched between the base layers to provide the battery with resistance to impact or piercing received from inside and outside.
[0009]
Furthermore, the case is molded (made into a bag) by heat fusion. For this purpose, the innermost layer of the laminate is made of a heat-adhesive resin layer. The heat-adhesive resin layer is formed of an acid-modified polyolefin-based resin that can be thermally fused to the metal of the electrode terminal T.
[0010]
By adopting such a configuration, the acid-modified polyolefin-based resin of the heat-adhesive resin layer has good heat-adhesive properties with respect to metals such as copper and aluminum while having self-heat-adhesive properties with each other. Therefore, the bag-shaped battery case having one end opened can be thermally bonded well by heat sealing and can be sealed.
[0011]
When a commonly used dry lamination method is used as a method of forming the above-described laminate, the laminate may be peeled between layers of the laminate used as the case due to a change with time such as storage. When analyzing the cause of the peeling, the electrolyte of the polymer battery is a carbonate-based organic solvent, so that the dry lamination adhesive, which is a solvent-based adhesive, can be dissolved by the electrolyte during long-term storage. found. That is, the electrolytic solution, which is a component of the battery, permeates the resin layer of the case over time to reach the adhesive interface where the adhesive is present, dissolves the adhesive, and finally the laminate is bonded. This is a phenomenon caused by delamination on the surface.
[0012]
Also, the battery may be used in a high temperature state or left unattended. If the battery case does not have heat resistance, the heat seal portion may be peeled off in a high temperature state, and the electrolyte or the like may leak. For example, it is required that an electronic device in which a battery is set is able to withstand even when left in a car (called a dashboard test). Specifically, it is required that the solution be kept at 100 ° C. for 5 hours so as not to leak liquid.
In order to solve the above problem, as a result of researching various laminated body configurations and respective materials, as a laminated body configuration that satisfies conditions to be provided as a case for a polymer battery, by adopting the following material configuration, The inventors have found that the above problems can be solved, and have completed the present invention.
[0013]
As the first base material layer, as a base material of the structure of the laminate, it is desirable that, during the production of the laminate such as printing and lamination, a material having strength and good workability is used, and as a surface layer of the battery. Various characteristics such as friction resistance are required.
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 the innermost layer is provided with a heat-adhesive resin. 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 thermo-adhesive resin layer.
The bonding of the metal foil layer and the second base material layer is performed by sandwich lamination using an adhesive resin. Further, in the above-mentioned material composition, an acid-modified polyolefin resin is used as the heat-adhesive resin, and the acid-modified polyolefin resin has a heat resistance of 100 ° C. or more.
[0014]
Hereinafter, the case for a polymer battery of the present invention will be described in detail.
In the present invention, in the structure of the laminate, when producing a laminate of a layer on the inner surface than the barrier layer, does not include an adhesive layer of an organic solvent type, the adhesion between each layer is an adhesive resin. And laminated by a sandwich lamination method, and the innermost layer is formed by extrusion-coating a thermo-adhesive resin.
However, in 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.
[0015]
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 gas barrier properties such as water vapor or the like in the middle, and the first, second, and second sheets having various strengths and durability outside or inside thereof. 3 is appropriately laminated, and furthermore, a heat-adhesive resin layer is laminated on the innermost layer.
[0016]
In the above configuration, an aluminum foil, a copper foil, or the like can be suitably used for the intermediate metal foil layer that imparts 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.
[0017]
As the first to third base layers, for example, a biaxially stretched polyethylene terephthalate film (hereinafter, PET film or PET), a biaxially stretched nylon film (hereinafter, ON film or ON), a polyethylene naphthalate film A polyimide film, a polycarbonate film, or the like can be used. However, when various processes including durability and workability and economy are taken into consideration, a PET film and an ON film are particularly suitable.
Here, comparing the properties of the PET film and the ON film, there is no special difference, but the PET film has low moisture absorption, is excellent in rigidity, scratch resistance, heat resistance, etc., and the ON film has a slightly high moisture absorption, Excellent flexibility, piercing strength, bending strength, cold resistance, etc.
The thickness of the film used as such a substrate layer is preferably 5 to 100 μm, more preferably 12 to 30 μm.
[0018]
As described above, the innermost thermo-adhesive resin layer has good thermo-adhesiveness to the metal of the electrode terminals in addition to the thermo-adhesiveness of itself, and also has a moisture In order to minimize infiltration, it is preferable that the material itself has low hygroscopicity or water absorption, and more preferably, it is stable without being swollen or eroded by the electrolytic solution.
[0019]
Examples of such a heat-adhesive resin include, for example, ethylene-vinyl acetate copolymer, ethylene-acrylate copolymer, ethylene-methacrylate copolymer, and one kind of the above copolymer in polyethylene or polypropylene. Alternatively, a polyolefin resin in which two or more kinds are blended can be used. Particularly, an acid-modified polyolefin resin, for example, an acid component such as an ethylene-acrylic acid copolymer or an ethylene-methacrylic acid copolymer is copolymerized. Polymerized and modified polyolefin resin, or polyethylene, polypropylene, or their copolymers of ethylene and propylene or other α-olefins, ethylene-vinyl acetate copolymer, ethylene-acrylate Copolymer, ethylene-methacrylic acid ester copolymer, Alternatively, polyolefin resins such as these terpolymers, 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 the anhydride is preferably used.
By using a resin having a melting point of 100 ° C. or more from these resins, the battery case has excellent heat resistance. When the melting point of the acid-modified polyolefin-based resin used for the heat-adhesive resin 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. is there.
[0020]
In the above, the acid component 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-adhesive resin layer is suitably in the range of 10 to 100 μm.
[0021]
As a method of laminating each layer as described above, in the present invention, as a laminating method inside the metal foil layer, an adhesive resin is melt-extruded between two layers to be bonded and sandwiched by a sandwich lamination method. to paste together.
As the adhesive resin, the above-mentioned acid-modified polyolefin-based resin is used.
In addition, the innermost heat-adhesive resin layer is formed by directly melt-extrusion coating an acid-modified polyolefin-based resin on the second or third base material layer, and is laminated. In forming the laminate of the sheet for a polymer battery case according to the present invention, the acid-modified polyolefin-based resin is bonded to the lamination inside the metal foil layer without employing a dry lamination method using an organic adhesive. However, in lamination outside the metal foil layer, a dry lamination method may be employed.
[0022]
【Example】
Hereinafter, the present invention will be further described with reference to the drawings of the embodiments.
However, the present invention is not limited to these drawings. Further, the same reference numerals are used for the parts having the same names in different drawings.
[0023]
FIG. 1 and FIG. 2 are schematic cross-sectional views each showing the configuration of an embodiment of the battery case sheet of the present invention.
The battery case sheet 10 shown in FIG. 1 is configured by laminating a first base layer 1a, a metal foil layer 2, an adhesive resin layer, a second base layer, and a thermoadhesive resin 3 in this order from the outside. It was done.
In the above configuration, the first base material layer 1a is a PET film or an ON film, the metal foil layer 2 is made of, for example, aluminum foil, and the adhesive resin layer and the heat adhesive resin layer 3 are made of an acid component. An acid-modified polyolefin resin having a content of 0.01 to 10% by weight is used.
[0024]
By adopting such a configuration, the battery case sheet 10 is made of the outermost first base material layer 1a, that is, a PET film or an ON film, and has mechanical strength such as tensile strength, piercing strength, and bending strength. In addition, the surface is provided with scratch resistance, water resistance, chemical resistance, heat resistance, cold resistance, etc., and an excellent barrier against water vapor and other gases due to an intermediate metal foil layer (for example, an aluminum foil layer). As described above, the innermost layer of the thermoadhesive resin layer 3 is made of an acid-modified polyolefin-based resin having an acid content of 0.01 to 10% by weight, for example. , And excellent heat sealability.
Further, regarding the barrier property, by using an aluminum foil having a thickness of, for example, 9 μm for the metal foil layer 2, a performance of water vapor permeability of 0.01 g / (m ² · 24 hr (40 ° C., 90% RH) or less can be easily obtained. It is easy to further improve this.
[0025]
The following specific examples are given as typical specific examples of the above-mentioned laminated structure.
(1) PET (thickness 12 μm) / AL (thickness 9 μm) / acid-modified polyolefin resin (thickness 15 μm) / PET (thickness 12 μm) / acid-modified polyolefin resin (thickness 30 μm)
(2) PET (thickness 12 μm) / AL (thickness 9 μm) / acid-modified polyolefin resin (thickness 15 μm) / ON (thickness 15 μm) / acid-modified polyolefin resin (thickness 30 μm)
(3) ON (15 μm in thickness) / AL (9 μm in thickness) / acid-modified polyolefin resin (15 μm in thickness) / PET (12 μm in thickness) / acid-modified polyolefin-based resin (30 μm in thickness)
(4) ON (thickness 15 μm) / AL (thickness 9 μm) / acid-modified polyolefin resin (thickness 15 μm) / ON (thickness 12 μm) / acid-modified polyolefin resin (thickness 30 μm)
[0026]
By adopting such a configuration, various mechanical strengths and tolerances are improved by the additional lamination of the third base layer 1b, as compared with the battery case sheet 10 having the configuration shown in FIG. At the same time, since both sides of the metal foil layer 2 are sandwiched between the second base material layer 1b and the third base material layer 1c, not only external impact and friction, but also physical and chemical actions, Also, the effect of improving the protection of the metal foil layer 2 and obtaining a more stable barrier property can be obtained.
[0027]
The battery case sheet 20 shown in FIG. 2 includes, in order from the outside, a first base layer 1a, a metal foil layer 2, an adhesive resin layer, a second base layer 1b, an adhesive resin layer, and a third base layer. It is formed by laminating a base material layer 1c and a heat-adhesive resin layer 3.
This configuration is different from the configuration of the battery case sheet 10 shown in FIG. 1 in that the performance of the second base material layer 1a inside the metal foil layer 2 as the intermediate layer is improved. A layer is added, and the third base material layer 1c is further laminated on the second base material layer 1b to further improve the strength as a battery case sheet.
[0028]
Also in this case, a PET film or an ON film is used for the first base layer 1a, the second base layer 1b, and the third base layer 1c.
In this case, the same type of film may be laminated on all the base layers. However, when a PET film is used for the first base layer 1a, the second base layer 1b or the third base layer may be used. It is more preferable to combine and laminate different kinds of films, such as using an ON film, as the material layer 1c, since the weak points of both can be complemented and the advantages can be provided.
[0029]
The structure shown in FIG. 2 is different from the structure of the battery case sheet 10 shown in FIG. 1 in that two base layers are provided inside the intermediate metal foil layer 2 to further improve the strength as a case. This is a laminated body. In the production of the laminate, the adhesive layer 5 between the first base material layer and the metal foil layer may be formed by any of a dry lamination method and a sandwich lamination method. Lamination on the inner side, that is, the lamination of the metal foil layer and the second base layer, the lamination of the second base layer and the third base layer, and the like are all performed by a sandwich lamination method using an adhesive resin, The heat-adhesive resin layer 3 is laminated by an extrusion coating method. Both the adhesive resin and the heat-adhesive resin layer in the sandwich lamination use an acid-modified polyolefin resin.
In addition, in order to improve the adhesiveness with the acid-modified polyolefin-based resin, the surface of the second base material layer or the third base material layer is coated with a known surface such as corona treatment, flame treatment, or plasma treatment. Processing can be performed. Further, in order to improve the adhesiveness between the heat-adhesive resin and the metal foil layer or the base material layer, it is also possible to heat the laminate after the lamination (after-heating).
[0030]
Accordingly, as shown in FIG. 2, a first base material layer 1 a is laminated on the outside of the metal foil layer 2, and a second base layer is formed on the inside of the metal foil layer 2 via the adhesive resin layer 4. A third base material layer 1c and a thermoadhesive resin layer 3 as an innermost layer are provided by an extrusion coating method via a material layer 1b and an adhesive resin layer 4. Regarding the lamination of the metal foil layer 2 and the second substrate layer 1b, and the lamination of the second substrate layer 1b and the third substrate layer 1c, the acid-denatured polyolefin-based resin is bonded to each other. A sandwich lamination method using a resin is used. Then, the innermost thermo-adhesive resin layer 3 is formed by an extrusion coating method. In this case, an ON film is preferable as the second and third base layers.
[0031]
By adopting such a configuration, the battery case sheet of the present invention improves the various mechanical strengths and resistances of the first, second, and in some cases, the third base material layers 1a, 1b, and 1c, Both sides of the metal foil layer 2 are sandwiched between a first base material layer 1a and a second base material layer 1b, and a third base material layer 1c is further laminated on the inside thereof. This has the effect of improving the strength against piercing and the like, protecting the metal foil layer, and obtaining more stable barrier properties as a battery sheet.
[0032]
In the case of printing characters, pictures, and the like on the surface of the battery case sheets 10 and 20 having the configuration shown in FIGS. 1 and 2, the inner surface (laminated surface) of the outermost first base material layer is formed. By printing in advance by a so-called back printing method and laminating the next layer on this surface to complete the battery case sheet, a printed image that is not damaged by surface friction or the like can be formed.
[0033]
【The invention's effect】
As described in detail above, according to the present invention, it is lightweight, thin, flexible, and has various mechanical strengths and heat resistances, as well as performance such as water vapor and other gas barrier properties, heat sealing properties, and workability. It is possible to provide an excellent battery case sheet with good productivity.
By using a laminate in which the solvent-based adhesive layer was not used for the laminate inside the metal layer, peeling by the electrolytic solution of the battery was eliminated.
Further, by using an acid-modified polyolefin-based resin having a melting point of 100 ° C. as the adhesive resin layer and the heat-adhesive resin layer, even if the battery is kept at a high temperature, a peeling phenomenon occurs in the seal portion of the battery case. The electrolyte no longer leaked.
[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.
FIG. 2 is a schematic cross-sectional view showing the configuration of another embodiment of the battery case sheet of the present invention.
FIGS. 3A and 3B are a perspective view and a cross-sectional view taken along line XX of the battery of the present invention.
[Explanation of symbols]
D Battery T Electrode terminal C Cell P Case 1a First base layer 1b Second base layer 1c Third base layer 2 Metal foil layer 3 Thermal adhesive resin layer 4 Adhesive resin layer 5 Adhesive layer 6 Seal Parts 10, 20 Battery case sheet

Claims (2)

A battery case sheet for storing a battery constituent material therein and used for forming a battery, comprising: a first base layer / metal foil layer / adhesive resin layer / second base layer / thermal bonding The metal foil layer and the second base material layer, and the second base material layer and the heat-adhesive resin are stacked by sandwich lamination or extrusion coating. A sheet for a polymer battery case, wherein the adhesive resin layer and / or the heat adhesive resin layer are made of an acid-modified polyolefin resin. The sheet for a polymer battery case according to claim 1, wherein the acid-modified polyolefin-based resin has a melting point of 100 ° C or higher.

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