JPH10261386A - Battery case and battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce short-circuiting between electrode terminals in an electrode terminal sealing part to improve reliability and stability in manufacturing a battery, by adopting the thermoplastic resin layer of a polymer laminated body, composed of at least an aluminum layer/an insulator layer/thermoplastic resin layer, as the inner surface of a sheathing body. SOLUTION: The case is constituted of a polymer laminated body, having an insulator layer having a melting point higher than that of the thermoplastic resin, between an aluminum layer and a thermoplastic resin layer such as heat sealable polyethylene or an ionomer resin, etc. The insulator layer is composed of a thermoplastic resin, a thermosetting resin, an insulating ceramics, or a ceramic particle dispersing element, etc., having a give melting point and electric conductivity; and is considering adhesion too. A protective layer can be provided on the surface of an aluminum layer which is a water permeable barrier layer. The case of the polymer laminated body, having the thermoplastic resin layer as an inner surface, has an unit cell in the inside, and seals an electrode terminal connecting the sheathing body inside and outside. Therefore, short-circuiting between an electrode terminal and the aluminum layer can be eliminated when the sheathing body is sealed by a heat fusion.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a package for a non-aqueous battery and a non-aqueous battery using the package.

[0002]

2. Description of the Related Art Non-aqueous batteries such as lithium batteries and lithium ion batteries are used as power sources for portable devices such as personal computers, mobile phones, and video cameras, and their capacity and weight have been reduced. These batteries use an electrolytic solution as an ion transfer medium between the electrodes, and a metal can is used for a package to prevent liquid leakage. However, the weight of the metal can makes the whole battery heavy, making it difficult to reduce the weight. In order to reduce the package weight, a film battery and a manufacturing method using a polymer laminated sheet as an exterior material have been proposed (Japanese Patent Application Laid-Open Nos. 60-449568 and 60-6544).
No. 2).

On the other hand, in a battery using a polymer solid electrolyte as an ion transfer medium, a laminate in which a sheet-like electrode and a polymer solid electrolyte are laminated, or a polymer solid electrolyte layer is formed by applying a polymer solid electrolyte layer on the electrode surface. The laminated pair can be manufactured by processing into a predetermined shape. As described above, since a method such as sheet lamination or coating can be adopted, it is expected that the production process is excellent in mass productivity. Further, since the liquid leakage which can occur in the conventional electrolyte battery does not substantially occur, the production process can be easily controlled, and a higher voltage is expected by the series connection lamination of the electrode / polymer solid electrolyte / electrode laminate. I have.

Conventionally, a polymer sheet / aluminum sheet laminate capable of being heat-sealed has been used for the package of this solid electrolyte battery. In order to constitute a battery, an electrode for extracting a current from the electrode to the outside is used. It is necessary to enclose the terminals in a package. In the sealing of the electrode terminals, the aluminum layer of the polymer sheet / aluminum sheet laminate sometimes comes into contact with the electrode terminals at the time of fusion, resulting in a problem that the performance of the battery is reduced and the battery cannot be operated.

[0005]

DISCLOSURE OF THE INVENTION The present invention provides a light-weight, low-water-permeability, low-short circuit between electrode terminals, and excellent battery performance for use in batteries such as lithium batteries and lithium-ion batteries. It is an object of the present invention to provide an exterior body capable of performing the above-mentioned operations, and to provide a lightweight battery excellent in battery performance and packaged with the exterior body.

[0006]

Means for Solving the Problems The present inventors have studied in view of the above problems, and as a result, have found that an aluminum layer and a thermoplastic resin layer used for a battery package material are fused to an aluminum layer. By introducing a polymer layer having a melting point higher than the melting point of the thermoplastic resin layer between the layers of the thermoplastic resin layer, the battery using this package material has reduced electrode terminal short-circuiting property and has a low battery performance. And found that the present invention was completed.

That is, the present invention provides (1) a polymer laminate having at least the structure of aluminum layer / insulator layer / thermoplastic resin layer, wherein the thermoplastic resin layer of the polymer laminate is formed on the inner surface of the exterior body. And (2) a battery sealed with the battery exterior of (1).

Hereinafter, the present invention will be described in detail. The exterior body material of the present invention has a structure in which a thermoplastic resin sheet and an aluminum sheet are laminated, and the exterior body can be sealed by fusing the thermoplastic polymer layer having the laminated structure. Things. Further, the aluminum layer having the laminated structure functions as a water-permeable barrier layer to prevent water from entering the exterior from the exterior.

The outer package of the present invention is formed of a polymer laminate, and the polymer laminate has a higher melting point between the aluminum layer and the thermoplastic resin layer which can be fused than the polymer constituting the thermoplastic resin layer. It is necessary to have at least a laminate structure having an insulator layer. The battery of the present invention, which is sealed with the package, has a structure in which a unit cell is disposed inside, and electrode terminals for connecting the inside and outside of the package are sealed with the package. In the conventional exterior body, there is a problem that a short circuit may occur between the electrode terminal and the aluminum layer when the exterior body is sealed by heat sealing in the electrode terminal sealing portion.

According to the present invention, an insulator layer is arranged between an aluminum layer of a polymer laminate forming an exterior body and a thermoplastic resin layer which can be heat-sealed, and the exterior body is formed so that the thermoplastic resin layer becomes an inner surface. By manufacturing, the short circuit between the electrode terminals, which has been a problem in the past, is greatly reduced, and the reliability and stability of the battery performance are greatly improved. The substance constituting the insulator layer in the outer package of the present invention needs to have a melting point higher than the melting point of the polymer of the thermoplastic resin layer or a substance that does not cause heat flow, and further, has an electric conductivity of 10 ^−8.
S / cm or less, preferably 10 ^-9 S / cm or less is required. It is preferable that the melting point of the substance forming the insulator layer is higher than the melting point of the thermoplastic resin forming the thermoplastic resin layer by 20 ° C. or more, preferably 30 ° C. or more. Therefore, the outer package can be formed by forming a thermoplastic resin, a thermosetting resin, an insulating ceramic, a ceramic particle dispersion, or the like having a higher melting point than the fusion layer polymer into a layer, and the thermoplastic resin that can be thermally fused is formed. The material can be selected in consideration of the melting point of the resin layer polymer, the adhesion to the thermoplastic resin layer, and the adhesion to the aluminum layer.

As the material of the thermoplastic resin layer capable of being heat-fused of the outer package of the present invention, aliphatic polyamide such as polyethylene, polypropylene, nylon, ionomer resin, polyester, nylon, aromatic polyamide, vinylidene fluoride, etc. Polymer, vinylidene chloride polymer,
Polymers such as polyphenylene oxide can be used. Of these thermoplastic resins, polyethylene and ionomer resins have high electrode terminal adhesion and sealing properties and are preferred as the outer package. Further, in order to improve the adhesiveness of the laminated layers and the adhesiveness to the electrode terminals, the surface of the thermoplastic resin layer which can be thermally fused can be subjected to oxidation treatment, coating, or the like.

Specific examples of the laminated structure of the outer package of the present invention include aluminum / polyethylene terephthalate / polyethylene, aluminum / polypropylene / polyethylene, and aluminum / nylon / ionomer resin. A protective layer such as a polymer layer of polyethylene terephthalate, nylon or the like may be further provided on the surface of the aluminum layer of the polymer laminate constituting the outer package of the present invention. Aluminum layer / insulator layer /
A structure in which a unit laminate of a thermoplastic resin layer is further laminated may be used. Further, a polymer laminate obtained by removing a part of the aluminum layer of the polymer laminate,
It can be used as a polymer laminate for an exterior body of the present invention, and the electrode terminal portion is sealed at a portion not including the aluminum layer.

The aluminum used in the present invention is preferably metallic aluminum or an aluminum alloy because of its light weight and excellent workability. If necessary, a substitute metal can be used.
In the present invention, as a lamination method, a method of laminating sheets by heat lamination and fusion, a method of casting or extruding a polymer melt on a substrate, a method of casting a polymer solution or a polymer precursor in a liquid state are possible. . This laminate structure can be formed in consideration of the water-permeable barrier properties required for the package, the sealing method, and the adhesion of the electrode terminals.

The aluminum layer of the polymer laminate of the present invention is formed by a method of laminating a thermoplastic polymer sheet in the form of a sheet, a vapor deposition method or the like. Examples of the method for sealing the battery outer package of the present invention include heat sealing, impulse sealing, a method using frictional heat such as spin welding, laser, infrared radiation, external heating such as hot jet, high frequency sealing, and internal heating such as ultrasonic sealing. Can be used. Which sealing method to use may be determined in consideration of the type and structure of the polymer laminate material constituting the outer package. Further, the package can be formed by bonding the polymer laminate materials with an adhesive, a pressure-sensitive adhesive or the like.

The water permeability of the battery casing of the present invention is 1
g / m ² · 24 hr or less. This water permeability is preferably low for a non-aqueous battery, preferably 0.2 g / m ^2.
・ 24 hr or less, more preferably 0.1 g / m ²・ 2
It is 4 hours or less. A battery using a package material having a water permeability of more than 1 g / m ² · 24 hr is not preferable because the battery structural elements inside the package are deteriorated by water absorption and the battery capacity is reduced. In addition, the internal electrolyte material is decomposed due to the water absorption, which may cause gas generation, which is not preferable. The amount of water permeation can be determined by enclosing a water-absorbing material such as anhydrous calcium chloride inside the package, keeping the package in a predetermined atmosphere, and measuring the weight increase.

In the present invention, the unit cell disposed inside the outer package is a non-aqueous battery and is a non-aqueous organic solvent or non-solvent battery. Examples of this battery include batteries such as lithium batteries, lithium ion batteries, sodium batteries, and air batteries, and electrochemical devices such as electric double layer capacitors and electrochromic devices. In the present invention, these are collectively referred to as batteries.

For example, as a unit cell, a battery can be constituted by various electrode materials as a primary battery and a secondary battery. For example, lithium, as an electrode material used for a lithium ion battery, as a positive electrode material lithium cobaltate, lithium nickelate, lithium manganate, and the like,
As the negative electrode material, a carbon material such as graphite or coke, a lithium metal, or a material capable of forming an alloy with lithium or an intermetallic compound can be used. Usually, a form in which these electrode materials are applied together with a binder in a powder form, or a continuous form produced by a method such as sintering, rolling, vapor deposition, or sputtering can be used. A current collector may be provided on this electrode.

As a medium for transferring ions between electrodes, a material obtained by impregnating a non-aqueous solvent-based electrolyte solution into a porous sheet;
A swollen material, an ion-coordinating polymer, a material containing a movable ion in a ceramic material, or the like can be used. As a configuration of the unit cell, an element structure including a positive electrode / an ion transfer medium / anode and a structure in which the element structures are stacked in series or in parallel can be used. Further, an electrode terminal for extracting a current from the electrode is connected to the electrode to form a battery structure. As the shape of the unit cell, a sheet shape, a rectangular parallelepiped shape, a roll shape, or the like can be used. As described above, the battery component, structure, and form of the present invention can be selected from various types according to the application to be used. The structure of the exterior material can be designed in accordance with the structure of these unit cells, and the unit cells are arranged inside the outer case, and the electrode terminals are sealed inside and outside the outer case to form a battery. It can be.

As described above, the battery of the present invention is industrially preferable because it is lightweight, has excellent battery performance stability and safety, and can reduce the failure rate in production. Hereinafter, the battery of the present invention will be described based on examples.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION

<Preparation of lithium-ion secondary battery> A slurry in which needle coke was used as a negative electrode active material, polyvinylidene fluoride was used as a binder (the amount of binder was 7% by weight of the active material) and dispersed in an N-methylpyrrolidone solvent was applied on a metal copper sheet, After drying to form a coating film, the film was heated and pressed at a temperature of 110 ° C. to obtain an electrode thickness of 133 μm. In addition, lithium cobalt oxide is used as a positive electrode active material, polyvinylidene fluoride is used as a binder (the amount of the binder is 10% by weight of the positive electrode active material), and carbon black (3% by weight of the positive electrode active material) is used as a conductive aid on an aluminum sheet in the same manner as the negative electrode. And heated and pressed to prepare a positive electrode sheet (film thickness 110 μm).
After cutting the electrode sheet into a predetermined shape, a metal aluminum sheet strip and a metal copper sheet strip were ultrasonically welded to the current collector exposed surface (opposite to the electrode application surface) as positive and negative electrode terminals, respectively. A poly (vinylidene fluoride-hexafluoropropylene) copolymer (hexafluoropropylene 3% by weight) was heated and extruded at a temperature of 190 ° C. to produce a 50 μm-thick polymer sheet. An electron beam (irradiation amount: 15 Mrad) was applied to the polymer sheet to crosslink the polymer. The sheet is made of Freon HFC134
After heat impregnation with a, the mixture was introduced into a heating furnace and foamed and stretched to prepare a foam sheet (foaming ratio 4 times, film thickness 70 μm). Then, the foamed sheet was subjected to an electrolytic solution (ethylene carbonate (EC) / propylene carbonate (PC) / γ-
Lithium in a mixed solvent of butyl lactone (BL) = 1/2
(A solution in which BF ₄ was dissolved at 1.5 mol / liter) and heated at 90 ° C. for 3 hours to prepare a hybrid electrolyte impregnated with the electrolyte. Next, a positive electrode sheet, a hybrid electrolyte, and a negative electrode sheet having a predetermined shape were laminated and heated and pressed to prepare a laminate (thickness of the laminate was 3).
40 μm). The charge / discharge characteristics of the battery were evaluated at 4.2 V after a constant current (current density of 1 mA / cm ² ) at a temperature of 25 ° C.
2.7V cut constant current (current density 1)
mA / cm ² ).

[0021]

Example 1 Oriented nylon sheet (film thickness 12 μm), aluminum foil (7 μm), polypropylene sheet (film thickness 15 μm), polyethylene sheet (film thickness 50 μm)
m) were sequentially laminated to prepare a polymer laminate sheet.
The polymer laminate sheet is cut and heat-sealed so that the polyethylene layer becomes the inner surface, and a 10 cm square envelope (exterior body)
Was prepared. 9cm square electrode sheet and 95mm
A battery laminate in which corner hybrid electrolyte sheets were laminated was put in, and the strip electrode terminals of each of the positive and negative electrodes having a width of 10 mm protruded outside the envelope. In the heat sealing of the sealing portion, heat sealing was performed while applying a pressure of about 1 kg / cm ² using a sealer heated at 130 ° C. Thus, five batteries were produced. As a result of charging and discharging the batteries, no short circuit between the electrode terminals was observed in any of the five batteries, and charging and discharging were possible. The initial discharge amount was 251 mAh on average, and charging and discharging were possible repeatedly. This battery was left in a charged state for one month (4
(0 ° C., humidity 90%), the discharge amount was 236 mAh on average. In addition, anhydrous calcium chloride was sealed in an envelope separately prepared, and left for one month in an atmosphere of 40 C and a humidity of 90% to evaluate weight increase. As a result, 0.02 g / m ² · 24 h
r or less.

[0022]

Comparative Example 1 A polymer laminate sheet was prepared by sequentially laminating an oriented nylon sheet (12 μm in thickness), an aluminum foil (7 μm), and a polyethylene sheet (50 μm in thickness). A battery was produced using an envelope obtained by processing the polymer laminate sheet in the same manner as in Example 1. 5 in the same operation
Batteries were produced. As a result of the same evaluation as in Example 1, short-circuiting between the electrodes was observed in two of the five batteries. The initial charge amount is 146 mAh on average for 5 batteries, and the charge state is
The amount of discharge (average of five batteries) after standing for a month was 120 mAh.

[0023]

Example 2 A polymer laminate sheet was prepared by sequentially laminating a polyethylene terephthalate sheet (thickness: 12 μm), an aluminum foil (thickness: 7 μm), a polyethylene terephthalate sheet (thickness: 12 μm), and a polyethylene sheet (thickness: 50 μm). The polymer laminate sheet was heat-sealed so that the polyethylene layer was on the inner surface to prepare an envelope (exterior body), and 10 battery laminates in which a 50 mm square positive electrode and a negative electrode were laminated with a 55 mm square hybrid electrolyte were laminated. The stacked body was placed in an envelope and then heat-sealed to produce a battery. The heat sealing conditions were the same as in Example 1, and the heating temperature of the heat sealer was 130 ° C.
The test was performed at kg / cm ² . The same operation was repeated to produce five batteries. The initial discharge amount (average of 5 cells) of this battery was 758 mAh, and after leaving the battery in a charged state for one month in an atmosphere of 40 ° C. and 90%, the evaluated discharge amount (average of 5 cells) was 716 mAh. No deformation of the battery structure due to this standing was observed. Also, anhydrous calcium chloride was sealed in a separately prepared envelope, and left for one month in an atmosphere of 40 ° C. and 90% humidity to evaluate the weight increase.
m ² · 24 hr or less.

[0024]

Comparative Example 2 A polymer laminate sheet was prepared by sequentially laminating a polyethylene terephthalate sheet (film thickness 12 μm), an aluminum foil (film thickness 7 μm), and a polyethylene sheet (film thickness 50 μm). A battery was produced using an envelope (outer body) obtained by processing the polymer laminate sheet in the same manner as in Example 2 (five batteries). As a result of performing the same evaluation as in Example 2, short-circuit between the electrodes was observed in one of the five batteries, the initial charge amount (average of five cells) was 604 mAh, and the discharge amount (5 Average) was 92 mAh.

[0025]

According to the battery outer package of the present invention, the short circuit between the electrode terminals of the electrode terminal sealing portion of the battery using the same is greatly reduced, and the reliability and stability of the battery production are greatly improved. It is very useful industrially because it enables it.

Claims (2)

[Claims] At least an aluminum layer / insulator layer /
An outer package for a battery, formed from a polymer laminate material having a configuration of a thermoplastic resin layer, wherein the thermoplastic resin layer of the polymer laminate material is formed to be an inner surface of the outer package. 2. A battery sealed with the battery casing according to claim 1.