JP4294770B2 - Polymer battery case sheet - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a battery case sheet that stores battery constituent materials, and more particularly to a sheet that can be suitably used for a case of a sheet-like battery.
[0002]
[Prior art]
Conventionally, a metal case has been used in most cases as a case for storing battery constituent materials. However, along with the development and widespread use of various electronic devices such as notebook computers and mobile phones, their weight and thickness have been reduced, and the batteries used for these have been made as light as possible and used. The battery itself is required to be reduced in weight and thickness so that the battery space in the device can be reduced.
[0003]
In order to meet such demands, for example, various sheet batteries that are light and thin in sheet form by introducing a polymer material into battery electrodes and electrolytes have been researched and developed. However, regarding the battery case used for these sheet-like 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, etc. are comprehensive. 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 of which is light and thin, in addition to its strength, heat resistance, durability, water vapor and other gas barrier properties, sealing properties, An object of the present invention is to provide a battery case sheet that is excellent in performance and workability, such as adhesion to an electrode terminal, and that can be suitably used for a lightweight and thin battery case with high productivity.
Conventionally, in order to form a case of a polymer battery, a laminate made of a base film, a barrier material, and a heat-adhesive resin has been used. In some cases, delamination occurred.
Moreover, although the modified | denatured polyethylene like ethylene methacrylic acid etc. was used for the thermoadhesive resin of the innermost layer of the laminated body of the conventional battery case, severe conditions (for example, in a high temperature state) at the time of the use of the said battery are used. Use)).
The present invention is a sheet used for a case for housing a polymer battery, which is excellent in water vapor and other gas barrier properties, has mechanical strength such as puncture resistance, and can be used at high temperatures. In contrast, a stable configuration is provided.
[0005]
[Means for Solving the Problems]
A battery case sheet used for forming a battery by storing battery constituent materials therein, the first base layer / metal foil layer / adhesive resin layer / second base layer / heat It is formed of a laminate having an adhesive resin layer configuration, and is a laminate in which the metal foil layer and the second substrate layer, and the second substrate layer and the thermal adhesive resin are laminated by sandwich lamination or extrusion coating. And the adhesive resin layer and / or the thermal adhesive resin layer is a sheet for a polymer battery case made of an acid-modified polyolefin resin, and the acid-modified polyolefin resin has a melting point of 100 ° C. or higher. Including.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a schematic cross-sectional view showing a configuration of an example of a battery case sheet of the present invention. FIG. 2 is a schematic cross-sectional view showing the configuration of another example of the battery case sheet of the present invention. 3A is a perspective view, and FIG. 3B is a cross-sectional view taken along the line XX, illustrating the polymer battery of the present invention.
As shown in FIG. 3, the polymer battery in the present invention is one in which the battery body of the electrode terminal T extended from the cell C is hermetically packaged by a case P. Since the electrode terminal T protrudes outside the case, a part of the electrode terminal T is bonded to the case inner surface resin at the seal portion of the case.
The battery case sheet having the above-described configuration is stacked so that the heat-adhesive resin layers are in contact with each other, heat-sealing the peripheral edge portion to form a bag-shaped battery case with one end opened, and the inside is positive and negative Stores battery components such as electrodes and electrolytes, extends the electrode terminals from the inside to the outside of the case, and heats the openings between the heat-adhesive resins in 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.
Therefore, in the heat-adhesive resin layer of the sheet, the electrode terminals formed of a conductive material such as a copper foil and an aluminum foil, which are the materials for forming the electrode terminals T, at the same time have heat-bonding properties to each other. Also, a resin having thermal adhesiveness is used.
[0007]
In the polymer battery case sheet, the laminate is composed of a metal foil layer and a heat-adhesive resin layer for barrier properties with an external base material layer. In order to prevent pinholes from being pierced and torn, second and third base material layers are further formed between the metal foil layer and the thermoadhesive 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 either the base material layer or the heat-adhesive resin layer is laminated on both sides thereof. The foil layer is protected and cracks and pinholes are prevented from being generated, so that 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, and the heat of the innermost layer. 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 non-conductive materials, the battery case sheet is non-conductive. Acts as a conductive sheet.
[0008]
Furthermore, as a result of various studies, the layer structure of the laminated body used for the battery case is that the surface side as the case is the first base material layer, the barrier layer is laminated, and the first layer is formed inside the barrier layer. By laminating the two base material layers, the barrier layer was sandwiched between the base material layers, and the battery was given resistance to impact or piercing received from the outside.
[0009]
Further, the case is molded (bag making) by heat fusion, and for this purpose, the innermost layer of the laminate is a heat-adhesive resin layer. The heat-adhesive resin layer is formed of an acid-modified polyolefin resin that can be heat-sealed 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 self-adhesiveness to each other, and at the same time has good thermal adhesion to metals such as copper and aluminum. Therefore, the bag-shaped battery case having one end opened can be favorably thermally bonded by heat sealing and sealed.
[0011]
When a generally used dry lamination method is used as a method of forming the laminate as described above, peeling may occur between the layers of the laminate used as the case due to changes over time such as storage. When the cause of the peeling was analyzed, the electrolyte of the polymer battery is a carbonate-based organic solvent. Therefore, the dry-lamination adhesive, which is a solvent-based adhesive, can be dissolved by the electrolyte during long-term storage. found. In other words, the electrolyte that is a constituent of the battery penetrates the resin layer of the case over time, reaches the adhesive interface where the adhesive is present, dissolves the adhesive, and the laminate is finally bonded. This is a phenomenon caused by delamination on the surface.
[0012]
In addition, the battery may be used or left in a high temperature state. If the battery case is not heat resistant, the heat seal part may be peeled off at a high temperature, and the electrolyte or the like may leak. For example, it is required to withstand even when an electronic device in which a battery is set is left in a vehicle (called a dashboard test). Specifically, it is required to hold for 5 hours in an environment of 100 ° C and not leak.
As a result of studying various laminate configurations and respective materials for the above problems, as a laminate configuration satisfying the 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]
The first base material layer is preferably a base material having a laminate structure, such as printing, lamination, etc., which has strength and good workability, and is used as a battery surface layer. Various characteristics including friction resistance are required.
In addition to polymer batteries, battery cases need 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, the 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 configuration of the present invention includes at least a barrier layer made of a metal foil and a base material layer and a thermoadhesive resin layer.
Bonding of the metal foil layer and the second base material layer is performed by sandwich lamination using an adhesive resin. Furthermore, in the above material structure, 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 higher.
[0014]
Hereinafter, the case for the polymer battery of the present invention will be described in detail.
In the present invention, in the construction of the laminate, when producing a laminate having a layer on the inner surface of the barrier layer, an adhesive layer of an organic solvent type is not included, and an adhesive resin is used for adhesion between the layers. They are used and laminated by a sandwich lamination method, and the innermost layer is formed by extrusion coating of a heat-adhesive resin.
However, in the lamination outside the metal foil layer, the lamination may be performed by the dry lamination method.
Thus, by not providing a solvent-based adhesive layer in the stack inside the metal foil layer, the electrolyte solution penetrates into the adhesive interface, thereby dissolving the adhesive layer and delamination between the layers of the laminate. There is no longer a risk 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 battery case sheet of the present invention uses a metal foil layer excellent in water vapor and other gas barrier properties in the middle as described above, and the first, second, and second excellent in various strengths and resistances on the outside or inside thereof. 3 substrate layers are appropriately laminated, and further, a thermoadhesive resin layer is laminated on the innermost layer.
[0016]
In said structure, aluminum foil, copper foil, etc. can be used suitably for the intermediate | middle metal foil layer which provides gas-barrier property. Among them, aluminum foil is most preferable because it is relatively inexpensive and has excellent workability such as bonding. The thickness of such a metal foil layer is suitably 5 to 25 μm.
[0017]
Examples of the first to third substrate layers include a biaxially stretched polyethylene terephthalate film (hereinafter referred to as PET film or PET), a biaxially stretched nylon film (hereinafter referred to as ON film or ON), and a polyethylene naphthalate film. Polyimide film, polycarbonate film, etc. can be used, but PET film and ON film are particularly suitable when considering various properties including durability and processability and economy.
Here, when comparing the properties of PET film and ON film, it is not a big difference, but PET film has low hygroscopicity, excellent rigidity, scratch resistance, heat resistance, etc., ON film has slightly high hygroscopicity, Excellent flexibility, piercing strength, bending strength, cold resistance, etc.
The thickness of the film used as such a base material layer is preferably 5 to 100 μm, and more preferably 12 to 30 μm.
[0018]
As described above, the innermost heat-adhesive resin layer has good heat-adhesiveness to the metal of the electrode terminal in addition to self-adhesiveness between the self-adhesive layers, In order to minimize penetration, it is preferable that the material itself has low hygroscopicity or low moisture adsorption property, and more preferably is stable without being swollen or eroded by the electrolytic solution.
[0019]
As such a heat-adhesive resin, for example, ethylene / vinyl acetate copolymer, ethylene-acrylic acid ester copolymer, ethylene-methacrylic acid ester copolymer, and a kind of the above-mentioned copolymer in polyethylene or polypropylene Alternatively, polyolefin resins such as blends of two or more types can be used, but acid-modified polyolefin resins such as ethylene-acrylic acid copolymers and ethylene-methacrylic acid copolymers are preferably used. Polymerized and modified polyolefin resin, polyethylene, polypropylene, copolymers of ethylene and propylene and other α-olefins, ethylene-vinyl acetate copolymer, ethylene-acrylic acid ester Copolymer, ethylene-methacrylate copolymer, Or, to these polyolefin-based resins such as terpolymers, unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, maleic anhydride, citraconic anhydride, itaconic acid, 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 higher among these resins, the heat resistance as a battery case is excellent. If the melting point of the acid-modified polyolefin 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 case seal and the electrolyte may leak out. is there.
[0020]
Among 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 thermal adhesiveness with the metal is insufficient, and when the content of the acid component exceeds 10% by weight, the film forming property is inferior.
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, a sandwich lamination method in which an adhesive resin is melt-extruded and pressure-bonded between two layers to be bonded together is used. to paste together.
The above-mentioned acid-modified polyolefin resin is also used as the adhesive resin.
Further, the innermost heat-adhesive resin layer is laminated by directly melt-extrusion-coating an acid-modified polyolefin resin on the second or third base material layer. In the formation of a laminate for a polymer battery case sheet according to the present invention, an acid-modified polyolefin resin is used as an adhesive resin for the lamination inside the metal foil layer without adopting a dry lamination method using an organic adhesive. However, a dry lamination method may be employed for lamination outside the metal foil layer.
[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. The same reference numerals are used for portions having the same names in different drawings.
[0023]
FIG. 1 and FIG. 2 are schematic cross-sectional views each showing a configuration of an example of a battery case sheet of the present invention.
The battery case sheet 10 shown in FIG. 1 is configured by laminating a first base material layer 1a, a metal foil layer 2, an adhesive resin layer, a second base material layer, and a thermal adhesive resin 3 in order from the outside. It is a thing.
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 acid components. 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, the PET film or the ON film, and has mechanical strength such as tensile strength, piercing strength, bending strength, In addition, surface scratch resistance, water resistance, chemical resistance, heat resistance, cold resistance, and other resistance are provided, and an intermediate metal foil layer (for example, an aluminum foil layer) provides an excellent barrier against water vapor and other gases. As described above, the innermost heat-adhesive resin layer 3 is excellent in that, for example, an acid-modified polyolefin resin having an acid component content of 0.01 to 10% by weight is used. Heat sealability is imparted.
As for the barrier property, for example, by using an aluminum foil having a thickness of 9 μm for the metal foil layer 2, a water vapor permeability of 0.01 g / (m ² · 24 hr (40 ° C., 90% RH) or less can be easily obtained. It is also easy to level up this.
[0025]
As typical examples of the laminated structure, the following structures can be given.
(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 (thickness 15 μm) / AL (thickness 9 μm) / acid-modified polyolefin resin (thickness 15 μm) / PET (thickness 12 μm) / acid-modified polyolefin resin (thickness 30 μm)
(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 resistances are improved by the additional lamination of the third base material layer 1b as compared with the battery case sheet 10 having the configuration shown in FIG. In addition, 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 the impact and friction from the outside, other physical and chemical effects, but also the internal The protective effect of the metal foil layer 2 is improved even for the same action from the above, and there is an effect that 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 The substrate layer 1c and the thermoadhesive resin layer 3 are laminated.
This configuration improves the performance of the second base material layer 1a inside the metal foil layer 2 as an intermediate layer with respect to the configuration of the battery case sheet 10 shown in FIG. 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 material layer 1a, the second base material layer 1b, and the third base material layer 1c.
In this case, the same kind of film may be laminated on all the base material layers. However, when a PET film is used for the first base material layer 1a, the second base material layer 1b or the third base material is used. For the material layer 1c, it is more preferable to laminate different types of films such as using an ON film from the viewpoint that both weak points can be complemented and the advantages can be combined.
[0029]
The configuration shown in FIG. 2 further improves the strength of the case by providing two base material layers inside the metal foil layer 2 as an intermediate layer, compared to the configuration of the battery case sheet 10 shown in FIG. It was made into the laminated body made. 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 either dry lamination method or sandwich lamination method, but from the metal foil layer Lamination on the inner side, that is, lamination of the metal foil layer and the second base material layer, the second base material layer and the third base material layer, etc., are all made by sandwich lamination using an adhesive resin. The thermal 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 acid-modified polyolefin resin.
The second substrate layer or the third substrate layer has a known surface such as corona treatment, flame treatment, plasma treatment, etc. on its surface in order to improve adhesion with the acid-modified polyolefin resin. Processing can be performed. In addition, in order to improve the adhesion between the heat-adhesive resin and the metal foil layer or the base material layer, it is possible to press and heat the laminate after heating (after heat).
[0030]
Therefore, as shown in FIG. 2, the first base material layer 1 a is laminated on the outside of the metal foil layer 2, and the second substrate is placed on the inside of the metal foil layer 2 via the adhesive resin layer 4. Through the material layer 1b and the adhesive resin layer 4, the third base material layer 1c and the thermal adhesive resin layer 3 as the innermost layer are provided by an extrusion coating method. For the lamination of the metal foil layer 2 and the second base material layer 1b and the lamination of the second base material layer 1b and the third base material layer 1c, the acid-modified polyolefin resin is adhesive. A sandwich lamination method using resin is used. The innermost heat-adhesive resin layer 3 is formed by an extrusion coating method. In this case, an ON film is desirable as the second and third base material layers.
[0031]
By adopting such a configuration, the battery case sheet of the present invention is improved in various mechanical strengths and resistances by the first, second, and possibly third base material layers 1a, 1b, and 1c, Both sides of the metal foil layer 2 are sandwiched between the first base material layer 1a and the second base material layer 1b, and further the third base material layer 1c is laminated on the inside thereof. In addition to improving the strength against piercing and the like, the metal foil layer is protected, and a more stable barrier property can be obtained as a battery sheet.
[0032]
In the battery case sheets 10 and 20 having the configuration shown in FIGS. 1 and 2, when characters, patterns, etc. are printed on the surface, the inner surface (lamination surface) of the outermost first base material layer is used. 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 above in detail, according to the present invention, it is lightweight, thin, flexible, and has various mechanical strength and heat resistance, as well as performance and workability such as water vapor and other gas barrier properties, and heat sealing properties. It is possible to provide a battery case sheet excellent in productivity with high productivity.
By using a laminate that does not use a solvent-based adhesive layer for lamination inside the metal layer, the battery was not peeled off by the electrolyte.
In addition, by using an acid-modified polyolefin resin having a melting point of 100 ° C. as the adhesive resin layer and the thermal adhesive resin layer, even if the battery is in a high temperature state, a peeling phenomenon occurs in the seal part of the battery case. The electrolyte no longer leaks out.
[Brief description of the drawings]
FIG. 1 is a schematic cross-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 a configuration of another example of the battery case sheet of the present invention.
3A is a perspective view, and FIG. 3B is a cross-sectional view taken along the line XX, showing the battery of the present invention.
[Explanation of symbols]
D Battery T Electrode terminal C Cell P Case 1a 1st base material layer 1b 2nd base material layer 1c 3rd base material layer 2 Metal foil layer 3 Thermal adhesive resin layer 4 Adhesive resin layer 5 Adhesive layer 6 Seal Part 10, 20 Battery case sheet

Claims (2)

Inside housing the constituent materials of the battery, a sheet for a battery case used to form a battery, in order from the outside, the first base layer, a metal foil layer, the adhesive resin layer, the second group wood layer, heat-adhesive resin layer is formed of a stack of configurations laminated, the metal foil layer and the second base layer, and the second base material layer and the thermally adhesive resin layer is a sandwich lamination or extrusion A laminated body laminated by a coating method, and the adhesive resin layer and / or the thermal adhesive resin layer is made of an acid-modified polyolefin resin ;
The first base layer and the second base layer are either a biaxially stretched polyethylene terephthalate film, a biaxially stretched nylon film, or a polyethylene naphthalate film, and the first base layer and the second base layer A sheet for a polymer battery case, wherein the base material layer is composed of different films .   The polymer battery case sheet according to claim 1, wherein the acid-modified polyolefin-based resin has a melting point of 100 ° C. or higher.

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