JP2004095333A - Laminate film for battery and non-aqueous electrolyte secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress deformation such as the swelling of a battery even if gas is generated inside the battery. <P>SOLUTION: This laminate film 2 encloses and houses the element battery 1 and comprises a metal film 23 and a plastic film 21 laminated on the metal film 23, and at least one layer of a reinforcement film 22 made of a fiber reinforced composite material is laminated together with the metal film 23 and the plastic film 21. The reinforcement film 22 is laminated between the metal film 23 and the plastic film 21. <P>COPYRIGHT: (C)2004,JPO

Description

【００４５】
表１の結果から、繊維強化複合材料を設けたラミネートフィルム２を用いた実施例１〜５の非水電解質二次電池では、比較例１の電池と比べて膨れ量が格段に抑えられることがわかり、比較例１の電池と比べて容量維持率が改善されていることがわかる。
【００４６】
以上、本発明を若干の実施例により詳細に説明したが、本発明は上記実施例に限定されるものではなく、本発明の要旨を逸脱することなく種々の変形が可能である。
例えば、上記実施例５では、カーボン繊維／エポキシ樹脂の組み合わせによる繊維強化複合材料（ＣＦＲＰ）から成る補強膜２２を２層設けるようにしたが、いずれか一方の補強膜２２をガラス繊維／不飽和ポリエステルの組み合わせによる繊維強化複合材料から成るものとしたり、アラミド繊維強化複合材料から成るものとしたりすることも可能である。
また、上記実施例１〜５では、いずれも繊維強化複合材料に繊維径７μｍのものを用いているが、繊維径はこれに限定されるものではない。
【００４７】
【発明の効果】
以上説明したように、本発明によれば、ラミネートフィルムを構成する金属薄膜及びプラスチックフィルムとともに繊維強化複合材料から成る補強膜を積層するようにしたため、電池特性劣化の小さい非水電解質二次電池を提供することが可能となる。
【図面の簡単な説明】
【図１】非水電解質二次電池を示す分解斜視説明図である。
【図２】図１に示した非水電解質二次電池を組み立てた状態の斜視説明図である。
【図３】本発明のラミネートフィルムの一実施例を示す図２の封止部分の断面説明図である。
【図４】本発明のラミネートフィルムの他の実施例を示す図２の封止部分の断面説明図である。
【図５】従来のラミネートフィルムを示す図２の封止部分相当位置での断面説明図である。
【符号の説明】
１　素電池
２　ラミネートフィルム
２１　プラスチックフィルム
２２　補強膜
２３　アルミニウム薄膜（金属薄膜）[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a laminated film for a battery and a non-aqueous electrolyte secondary battery. More specifically, the present invention relates to a laminated film for a battery and a non-aqueous electrolyte secondary battery capable of suppressing deformation of the battery by laminating a reinforcing film made of a fiber-reinforced composite material together with a metal thin film and a plastic film.
[0002]
[Prior art]
2. Description of the Related Art In recent years, cordless and portable electronic devices such as mobile phones and notebook personal computers have been developed, and thin, small, and lightweight portable electronic devices have been developed one after another. In addition, the diversification of these devices has led to an increase in the amount of power consumption, and accordingly, there has been an increasing demand for higher capacity for batteries, particularly secondary batteries, which are energy sources for each electronic device.
[0003]
Conventionally used secondary batteries include lead-acid batteries and nickel-cadmium batteries, while nickel-metal hydride batteries and lithium-ion batteries have already been put into practical use as new secondary batteries. Since all the secondary batteries use a liquid as an electrolyte, there is a fear of liquid leakage.
[0004]
Therefore, a polymer lithium ion battery using a polymer gel swollen by an electrolytic solution as an electrolyte has been developed to eliminate such a concern. With the development of the polymer lithium ion battery, there is no fear of liquid leakage, and as a result, a thin, small, and lightweight secondary battery having a high energy density can be realized.
[0005]
Explaining the polymer lithium ion battery, for example, an active material composed of LiCoO ₂ and graphite is laminated on a positive electrode current collector made of an aluminum thin plate, and carbon, coke is produced on a negative electrode current collector made of a copper thin plate. , Graphite and the like are laminated, and these form an electrode. A thin-film separator made of polypropylene or polyethylene having pores is sandwiched between the two current collectors. Polyacrylonitrile (PAN), polyethylene oxide (PEO), It has a sandwich structure filled with a polymer gel electrolyte such as polyvinylidene fluoride (PVDF).
[0006]
A unit cell (unit cell) having such a sandwich structure is packaged with a laminated film as a container for enclosing, and a conventional laminated film 50 is made of, for example, an aluminum foil as shown in FIG. The structure is such that plastic films 51 and 53 are adhered to a metal thin film 52 as described above. Nylon, polyethylene, polypropylene, polyethylene terephthalate, or the like is used for one plastic film 51, and the other plastic film (heat-sealing resin layer) 53 is used for sealing by heat-sealing when a unit cell is packaged. For the purpose, polyolefin-based resins such as polyethylene, polypropylene, modified polyethylene, and modified polypropylene are used.
[0007]
[Problems to be solved by the invention]
However, as described above, when an aluminum laminate film is used for the exterior of a polymer lithium-ion battery, the battery can be made smaller, lighter, and thinner, but the strength is lower than that of a conventional metal container (battery can). In addition, when gas is generated inside the battery, even if the internal pressure is slightly increased, the battery swells, and not only does the battery performance deteriorate, but also there is no risk of damaging the outer container. There is a problem that it cannot be said, and solving this problem has been a conventional problem.
[0008]
The present invention has been made by paying attention to the conventional problems described above, and even if gas is generated inside the battery, a battery laminate film that can reduce deformation such as battery swelling and the like. It is intended to provide a non-aqueous electrolyte secondary battery.
[0009]
[Means for Solving the Problems]
The present inventors have conducted intensive studies to achieve the above object, and as a result, have found that the above object can be achieved by laminating a reinforcing film made of a fiber-reinforced composite material together with a metal thin film and a plastic film constituting a laminate film. The invention has been completed.
[0010]
That is, the laminated film for a battery of the present invention includes a metal thin film and a plastic film laminated on the metal thin film, and a reinforcing film made of a fiber-reinforced composite material is laminated at least one layer together with the metal thin film and the plastic film. There is a feature.
[0011]
On the other hand, the non-aqueous electrolyte secondary battery of the present invention includes a unit cell, a metal thin film and a laminate film containing the unit cell including a plastic film laminated on the metal thin film, and the laminate film includes: A reinforcing film made of a fiber reinforced composite material laminated at least one layer together with a metal thin film and a plastic film is provided.
[0012]
In the present invention, since the reinforcing film made of the fiber reinforced composite material is laminated together with the metal thin film and the plastic film constituting the laminate film, even if gas is generated due to various factors, the swelling of the battery is significantly suppressed. It becomes.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a nonaqueous electrolyte secondary battery to which the present invention is applied will be described in detail with reference to the drawings.
The non-aqueous electrolyte secondary battery of the present invention is typically a solid electrolyte battery or a gel electrolyte battery, in which a solid electrolyte or a gel electrolyte is provided between the positive electrode active material layer and the negative electrode active material layer. A unit cell is formed, and as shown in FIGS. 1 and 2, in a state where the unit cell 1 is wrapped with a laminate film 2, the periphery of the film is sealed by heat welding.
[0014]
The unit cell 1 is provided with a negative terminal lead 3 electrically connected to a negative electrode constituting the unit cell 1 and a positive terminal lead 4 electrically connected to a positive electrode. The terminal lead 3 and the positive terminal lead 4 are both drawn out of the laminate film 2.
[0015]
As described above, a conventional laminated film has, for example, a structure in which a plastic film is laminated with a metal thin film interposed therebetween.In the present invention, in order to increase mechanical strength, a part of the laminated film is used. A fiber reinforced composite (FRP) reinforced membrane is provided. However, the position of the reinforcing film is not limited.
For the reinforcing film, a fiber reinforced composite material (GFRP) using a combination of glass fiber / unsaturated polyester, a fiber reinforced composite material (CFRP) using a combination of carbon fiber / epoxy resin, an aramid fiber reinforced composite material (AFRP), and the like are used. be able to.
[0016]
Here, when a solid electrolyte battery or a gel electrolyte battery is considered as the non-aqueous electrolyte secondary battery, the polymer materials used for the polymer solid electrolyte include silicon gel, acrylic gel, acrylonitrile gel, and polyphosphazene modified polymer. , Polyethylene oxide, polypropylene oxide, and their composite polymers, crosslinked polymers, modified polymers and the like, and fluorine-based polymers such as poly (vinylidene fluoride), poly (vinylidene fluoride-co-hexafluoropropylene), poly ( Various types of vinylidene fluorolide-co-tetrafluoroethylene), poly (vinylidene fluorolide-co-trifluoroethylene), and the like, and mixtures thereof can be used, but of course, the present invention is not limited thereto.
[0017]
In addition, the solid electrolyte or the gel electrolyte laminated on the positive electrode active material layer or the negative electrode active material layer is a solution comprising a polymer compound, an electrolyte salt, and a solvent (and a plasticizer in the case of a gel electrolyte). Alternatively, it is obtained by impregnating the negative electrode active material layer, removing the solvent, and solidifying. A part of the solid electrolyte or the gel electrolyte laminated on the positive electrode active material layer or the negative electrode active material layer is impregnated into the positive electrode active material layer or the negative electrode active material layer to be solidified. In the case of a crosslinked system, it is then solidified by crosslinking with light or heat.
[0018]
Further, the gel electrolyte is composed of a plasticizer containing a lithium salt and 2 to 30% by mass of a matrix polymer. In this case, esters, ethers, carbonates and the like can be used alone or as one component of a plasticizer.
[0019]
In preparing the gel electrolyte, various polymers used to form the gel electrolyte can be used as the matrix polymer for gelling the carbonates. From the viewpoint of properties, it is desirable to use a fluorine-based polymer such as poly (vinylidene fluoride) or poly (vinylidene fluoride-co-hexafluoropropylene).
[0020]
The polymer solid electrolyte is composed of a lithium salt and a polymer compound that dissolves the lithium salt. Examples of the polymer compound include ether polymers such as poly (ethylene oxide) and cross-linked products, poly (methacrylate) ester-based, and acrylate-based polymers. , A fluorine-based polymer such as poly (vinylidene fluoride) or poly (vinylidene fluoride-co-hexafluoropropylene) or the like can be used alone or as a mixture. It is desirable to use a fluoropolymer such as (vinylidene fluoride) or poly (vinylidene fluoride-co-hexafluoropropylene).
[0021]
As the lithium salt to be contained in such a gel electrolyte or a solid polymer electrolyte, a lithium salt used in a usual battery electrolyte can be used. Examples of the lithium compound (salt) include the following. However, the present invention is not limited to these.
[0022]
That is, lithium chloride, lithium bromide, lithium iodide, lithium chlorate, lithium perchlorate, lithium bromate, lithium iodate, lithium nitrate, lithium tetrafluoroborate, lithium hexafluorophosphate, lithium acetate, bis (trifluoro) Lome chest Gandolfo sulfonyl), lithium _{imide, LiAsF 6, LiCF 3 SO 3} , LiC (SO 2 CF 3) 3, can be mentioned LiAlCl 4, LiSiF _6, and the like.
[0023]
These lithium compounds may be used alone or in combination of two or more, but it is preferable to use LiPF ₆ , LiAsF ₆ , and LiBF ₄ from the viewpoint of oxidation stability.
[0024]
The lithium salt can be carried out by dissolving the lithium salt in a plasticizer at a concentration of 0.1 to 3.0 mol / l in the case of a gel electrolyte, and preferably at a concentration of 0.5 to 2.0 mol / l. Perform by dissolving.
[0025]
The non-aqueous electrolyte secondary battery of the present invention can be configured in the same manner as a conventional lithium ion battery except that the above-mentioned gel electrolyte or solid electrolyte is used.
That is, as a negative electrode material for forming a lithium ion battery, a material that can be doped and dedoped with lithium ions, for example, a non-graphitizable carbon-based material or a carbon material of a graphite-based material can be used. More specifically, pyrolytic carbons, cokes (pitch coke, needle coke, petroleum coke), graphites, glassy carbons, and organic polymer compound fired bodies (phenolic resin, furan resin, etc.) at an appropriate temperature Carbon materials such as carbonized by firing), carbon fiber, activated carbon and the like can be used.
[0026]
In addition to the above-mentioned materials, as a material that can be doped and de-doped with lithium ions, a polymer such as polyacetylene or polypyrrole or an oxide such as SnO ₂ can be used. At the time of formation, a known binder or the like can be added.
[0027]
On the other hand, the positive electrode can be configured using a metal oxide, a metal sulfide, or a specific polymer as the positive electrode active material, depending on the type of the intended battery. For example, when a lithium ion battery is configured, as a positive electrode active material, a metal sulfide or oxide containing no lithium, such as TiS ₂ , MoS ₂ , NbSe ₂ , V ₂ O ₅ , or Li _x MO ₂ (where M represents one or more transition metals, and x varies depending on the charge / discharge state of the battery, and is usually 0.05 to 1.10.
[0028]
It is preferable to use Co, Ni, Mn, or the like as the transition metal M constituting the lithium composite oxide. Specific examples of such a lithium composite oxide include LiCoO ₂ , LiNiO ₂ , and LiNi _y Co _{1−. y} O ₂ (where 0 <y <1), LiMn ₂ O _{4, and the} like can be given.
These lithium composite oxides can generate a high voltage, and become a positive electrode active material with particularly excellent energy density. For the positive electrode, a plurality of types of the positive electrode active materials may be used in combination.When forming the positive electrode using the positive electrode active material, a known conductive agent or a binder may be added. Can be.
[0029]
【Example】
Hereinafter, the present invention will be described in more detail with reference to the drawings by using some examples and comparative examples.
[0030]
(Example 1)
The non-aqueous electrolyte secondary battery of this example was manufactured in the following manner.
First, a negative electrode was manufactured as follows.
90 parts by weight of the pulverized graphite carbon material powder and 10 parts by weight of poly (vinylidenefluoride-co-hexafluoropropylene) as a binder were mixed to prepare a negative electrode mixture, and the negative electrode mixture was further dissolved in a solvent. Was dispersed in N-methyl-2-pyrrolidone to obtain a slurry.
Next, using a strip-shaped copper foil having a thickness of 10 μm as the negative electrode current collector, the negative electrode mixture slurry was uniformly applied to one surface of the negative electrode current collector, dried, and then compression-molded by a roll press machine. It was prepared by cutting out to 52 mm × 320 mm.
[0031]
On the other hand, the positive electrode was produced as follows.
0.5 mol of lithium carbonate and 1 mol of cobalt carbonate were mixed and calcined in air at 900 ° C. for 5 hours to obtain a positive electrode active material (LiCoO ₂ ).
A mixture of 91 parts by weight of LiCoO ₂ as a cathode active material thus obtained, 6 parts by weight of graphite as a conductive agent, and 10 parts by weight of poly (vinylidenefluoride-co-hexafluoropropylene) as a binder was mixed. To prepare a positive electrode mixture, and this positive electrode mixture was dispersed in N-methyl-2-pyrrolidone to form a slurry.
Next, a 20 μm-thick strip-shaped aluminum foil was used as the positive electrode current collector, and the positive electrode mixture slurry was uniformly applied to one surface of the positive electrode current collector and dried, followed by compression molding with a roll press machine. It was prepared by cutting out to 50 mm × 300 mm.
[0032]
Further, a gel electrolyte was prepared as follows.
A plasticizer consisting of 42.5 parts by weight of ethylene carbonate (EC), 42.5 parts by weight of propylene carbonate (PC), and 15 parts by weight of LiPF ₆ was added to a poly (vinylidene fluoride-co-copolymer having a weight average molecular weight Mw of 600,000). A mixture of 10 parts by weight of hexafluoropropylene) and 60 parts by weight of dimethyl carbonate mixed and dissolved is uniformly applied and impregnated on the negative electrode and the positive electrode, and left at room temperature for 8 hours to vaporize dimethyl carbonate. And removed to obtain a gel electrolyte.
[0033]
Next, the positive electrode and the negative electrode, on which a gel electrolyte was formed by applying a gel electrolyte to volatilize the solvent to form a gel electrolyte membrane, were flatly wound so as to be aligned with each other, thereby producing a battery element having a capacity of 2 Wh.
[0034]
As shown in FIGS. 1 and 2, the non-aqueous electrolyte secondary battery is manufactured by sealing the periphery of the battery element 1 by heat welding while wrapping the battery element 1 with a laminate film 2. In this case, the laminated sheet 2 having a size of 7 × 4 cm was folded substantially at the center in the longitudinal direction, and three sides were decompressed and sealed, and the battery element 1 was sealed in the thus formed element container portion 1 a having a size of 4 cm square. . That is, the seal length on one side is 4 cm, the number of sides is 3, and the total seal length is 12 cm. The sealing conditions were 200 ° C., 5 seconds, width 5 mm, and sealing was performed so that the distance between the metal foils was 200 μm or less.
[0035]
The negative electrode terminal lead 3 electrically connected to the negative electrode of the unit cell 1 and the positive electrode terminal lead 4 electrically connected to the positive electrode are both drawn out of the laminate film 2.
[0036]
As shown in FIG. 3, the laminate sheet 2 has a structure in which a plastic film 21, a reinforcing film 22, an aluminum thin film (metal thin film) 23, and a heat sealing resin 24 are sequentially laminated from the outside (upper side in the figure). In the embodiment, the reinforcing film 22 is disposed between the plastic film 21 and the aluminum thin film 23, that is, at the position (1) in the figure.
A stretched nylon film is used for the outer plastic film 21 (a film made of polyethylene, polypropylene, polyethylene terephthalate, or the like can also be used). On the other hand, a heat-sealing resin positioned inside to seal by heat-sealing is used. For 24, a high-density polyethylene having a thickness of 100 μm was used. Further, for the reinforcing film 22, a fiber reinforced composite material (CFRP) having a fiber diameter of 7 μm by a combination of carbon fiber / epoxy resin was used.
[0037]
Note that a resin piece is applied to a portion of the electrode terminal that intersects with the heat-sealing resin 24, thereby avoiding a short circuit due to burrs and the like, and improving the adhesiveness between the terminal and the laminate film 2.
[0038]
(Example 2)
As the laminate sheet 2, a plastic film 21, an aluminum thin film (metal thin film) 23, a reinforcing film 22 made of a fiber reinforced composite material (CFRP) having a fiber diameter of 7 μm by a combination of carbon fiber / epoxy resin, and a heat sealing resin 24 are placed outside ( The one having a structure laminated in order from the upper side in the drawing), that is, a structure having the reinforcing film 22 disposed at the position (2) in the drawing between the aluminum thin film 23 and the heat sealing resin 24 was used. Except for this, a battery was fabricated in the same manner as in Example 1.
[0039]
(Example 3)
As the laminate sheet 2, a sheet having a structure having a reinforcing film 22 made of a fiber reinforced composite material (GFRP) having a fiber diameter of 7 μm and made of a combination of glass fiber and unsaturated polyester was used. ▼ position). Except for this, a battery was fabricated in the same manner as in Example 1.
[0040]
(Example 4)
As the laminate sheet 2, a sheet having a structure having a reinforcing film 22 made of an aramid fiber reinforced composite material (AFRP) having a fiber diameter of 7 μm was used (the location of the reinforcing film 22 is indicated by (1) in the figure). Except for this, a battery was fabricated in the same manner as in Example 1.
[0041]
(Example 5)
As shown in FIG. 4, as the laminate sheet 2, the FRP layer is further increased, a plastic film 21, a reinforcing film 22 made of a fiber reinforced composite material (CFRP) having a fiber diameter of 7 μm by a combination of carbon fiber / epoxy resin, and an aluminum thin film A structure in which a (metal thin film) 23, a reinforcing film 22 made of a fiber reinforced composite material (CFRP) having a fiber diameter of 7 μm by a combination of carbon fiber and epoxy resin, and a heat sealing resin 24 are sequentially laminated from the outside (upper side in the figure). (The location of the reinforcing film 22 is indicated by (1) and (3) in the figure). Except for this, a battery was fabricated in the same manner as in Example 1.
[0042]
(Comparative Example 1)
A laminated film (without CFRP) in which a plastic film, an aluminum thin film, and a heat sealing resin were sequentially laminated from the outside was used (see FIG. 5). Except for this, a battery was fabricated in the same manner as in Example 1.
[0043]
Each of the fabricated batteries of Examples 1 to 5 and Comparative Example 1 was charged at 4.2 V and stored in an oven set at an internal temperature of 60 ° C. for 3 months in order to make the batteries easily swell at an accelerated rate. The swelling after storage (increment from the battery thickness before storage) was measured, and 1C cycles were performed after storage, and the capacity retention rate after 10 cycles (discharge capacity after 10 cycles after storage / discharge capacity before storage (1C) During discharge)) was measured.
Table 1 shows the evaluation results of the batteries of Examples 1 to 5 and Comparative Example 1.
[0044]
[Table 1]

[0045]
From the results in Table 1, it can be seen that in the nonaqueous electrolyte secondary batteries of Examples 1 to 5 using the laminated film 2 provided with the fiber-reinforced composite material, the amount of swelling is significantly reduced as compared with the battery of Comparative Example 1. It can be seen that the capacity retention ratio is improved compared to the battery of Comparative Example 1.
[0046]
As described above, the present invention has been described in detail with some embodiments. However, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the gist of the present invention.
For example, in the fifth embodiment, two reinforcing films 22 made of a fiber reinforced composite material (CFRP) made of a combination of carbon fiber / epoxy resin are provided, but one of the reinforcing films 22 is made of glass fiber / unsaturated. It is also possible to use a fiber-reinforced composite material made of a combination of polyesters or an aramid fiber-reinforced composite material.
In Examples 1 to 5, the fiber reinforced composite material has a fiber diameter of 7 μm, but the fiber diameter is not limited to this.
[0047]
【The invention's effect】
As described above, according to the present invention, since a reinforcing film made of a fiber-reinforced composite material is laminated together with a metal thin film and a plastic film constituting a laminate film, a non-aqueous electrolyte secondary battery with small deterioration in battery characteristics is provided. Can be provided.
[Brief description of the drawings]
FIG. 1 is an exploded perspective view showing a non-aqueous electrolyte secondary battery.
FIG. 2 is a perspective explanatory view showing a state where the nonaqueous electrolyte secondary battery shown in FIG. 1 is assembled.
FIG. 3 is an explanatory cross-sectional view of a sealing portion of FIG. 2 showing one embodiment of the laminate film of the present invention.
FIG. 4 is an explanatory sectional view of a sealing portion of FIG. 2 showing another embodiment of the laminated film of the present invention.
FIG. 5 is an explanatory cross-sectional view showing a conventional laminated film at a position corresponding to a sealing portion in FIG. 2;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Unit cell 2 Laminate film 21 Plastic film 22 Reinforcement film 23 Aluminum thin film (metal thin film)

Claims (4)

A laminate film that wraps and accommodates the unit cells,
A metal thin film,
In a laminated film for a battery comprising a plastic film laminated on the metal thin film,
A laminated film for batteries, wherein a reinforcing film made of a fiber-reinforced composite material is laminated at least one layer together with the metal thin film and the plastic film. The laminated film for a battery according to claim 1, wherein the reinforcing film made of the fiber-reinforced composite material is laminated between the metal thin film and the plastic film. Unit cells,
A non-aqueous electrolyte secondary battery including a metal thin film and a laminate film that wraps and accommodates the unit cell including the plastic film laminated on the metal thin film,
A non-aqueous electrolyte secondary battery, wherein a reinforcing film made of a fiber-reinforced composite material laminated at least one layer with a metal thin film and a plastic film is provided on the laminate film. The non-aqueous electrolyte secondary battery according to claim 3, wherein a reinforcing film made of a fiber-reinforced composite material provided on the laminate film is laminated between the metal thin film and a plastic film.

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