JPS63221555A - Thin battery - Google Patents

Abstract

PURPOSE:To obtain a thin film battery having long term storage stability by forming an adhesive with specially treated modified polyolefin, powdery inorganic substance, and non-modified polyolefin resin. CONSTITUTION:An adhesive polyolefin component for sealant consists of modified polyolefin prepared by heating a polyolefin resin and an unsaturated resin having polar group under the existence of organic peroxide, powdery inorganic substance, and non-modified polyolefin resin. The composition of the component is 10-80 wt.% modified polyolefin, 5-50 wt.% powdery inorganic substance, and 10-80 wt.% non-modified polyolefin resin. By using this sealant having good adhesion, a thin film battery having long term storage stability can be obtained.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is a long-term battery that is characterized by sealing the periphery of an exterior plate that also serves as a current collector for both positive and negative electrodes with a sealing material that has improved adhesiveness. This invention relates to a thin battery with excellent storage stability.

[Technical background of the invention and its problems] Recently, as electronic devices have become smaller and thinner,
Even in batteries as their power source.

There is a strong demand for smaller and thinner devices. especially.

BACKGROUND ART So-called sheet batteries and paper batteries suitable for card-type electronic devices such as memory cards and IC cards have been put into practical use. In order to make these batteries thinner, the method of sealing the batteries has become a major technical issue.

For these thin batteries, a structure has been proposed in which the periphery of a flat exterior plate with both positive and negative electrodes, which also serves as a current collector, is sealed with a thermoadhesive resin.

This thermoadhesive resin is required to have the following properties. In other words, as the thickness of the positive and negative electrodes decreases, 1
There is a need for a sealing material that maintains sufficient insulation between the two electrodes, has good adhesion, does not leak electrolyte, and has excellent long-term storage stability. Furthermore, from the viewpoint of high energy density, lithium was used as the negative electrode active material, and a non-aqueous electrolyte in which an inorganic salt was dissolved in an organic solvent was used as the electrolyte. The development of so-called nonaqueous electrolyte lithium battery-based thin film batteries is actively underway. In that case, the sealing material must also have characteristics that prevent it from absorbing moisture that easily reacts with lithium from the outside, and that it is chemically stable to organic electrolytes and does not cause swelling.

Various polyolefin resins, fluorine resins, and modified products thereof have been proposed as heat-adhesive resins that satisfy these characteristics.
No. 8232, No. 460-14753, No. 60-1480
No. 50, No. 60-160559, No. 60-18535
No. 9, No. 60-185360, No. 60-220553
issue.

No. 61-68860, No. 61-185867.

No. 61-74256, No. 61-176054.

No. 61-185867 and the like are disclosed.

These methods utilize the fact that polyolefin resin is nonpolar and therefore has excellent chemical and electrical properties. However, polyolefin resins have poor adhesive properties, and therefore, the above-mentioned conventional technology proposes the use of modified products such as copolymers of ethylene and vinyl acetate, ionomer resins, or polyolefin resins grafted with unsaturated carboxylic acids. are doing.

However, it cannot be said that these modified products necessarily have sufficient adhesive properties to satisfy the above-mentioned required properties as a sealant, and batteries using these as a sealant have problems in long-term reliability. There is a need for a sealing material with even better adhesive properties.

Therefore, various improvement methods have been proposed in order to impart adhesive properties to polyolefin resins. As one of them,
The polyolefin resin is γ-methacryloyloxypropyltrimethoxysilane.

A method has been proposed for improving the adhesiveness of polyolefin resins by modifying them with a type of modifier selected from glycidyl methacrylate and an organic peroxide. however,
The improvement in adhesion of modified polyolefins obtained by this method is still not satisfactory.

Therefore, the object of the present invention is to improve the shortcomings of conventional thin film batteries. The object of the present invention is to provide a thin film battery with excellent long-term storage stability using a sealing material with excellent adhesiveness.

[Means to solve the problem]

The present invention has the following features: (1) A separator containing an electrolyte or a solid electrolyte diaphragm is formed between the positive electrode and the negative electrode inside the exterior plate consisting of a pair of opposing thin metal plates that also serve as current collectors, and the exterior plate 1. A thin battery whose periphery is sealed with a sealant, the sealant comprising each of the following components (a) to (c).

(a) is 10 to 80% by weight, (b) is 5 to 50% by weight,
An adhesive polyolefin composition characterized in that (c) is 10 to 80% by weight.

(a) Modified polyolefin obtained by heating a polyolefin resin and an unsaturated compound having a polar group in the presence of an organic peroxide (b) Powdered inorganic substance (c) Unmodified polyolefin resin (2) Polar 2. The thin battery according to claim 1, wherein the unsaturated compound having a group is an organic silane compound.

(3) The thin electronic IL according to claim 1, wherein the powdered inorganic substance is calcium carbonate.

(4) Claims characterized in that the polyolefin resin is a crystalline propylene polymer! The thin battery according to item 131.

The above objective has been achieved by providing the following.

Each component of the encapsulant composition used in the thin battery of the present invention will be explained in detail.

The modified polyolefin used in this invention is obtained by heating a polyolefin resin and an unsaturated compound having a polar group in the presence of an organic peroxide.

The polyolefin resin is a crystalline homopolymer of propylene, a copolymer with propylene, and the content thereof is about 3
Crystalline propylene polymers such as binary or more block or random copolymers with 0% by weight or less of other α-olefins (e.g., ethylene, butene, pentene, hexene, heptene, etc.) or with a density of 0.93 g /cm'' or more, and ethylene and copolymers with other α-olefins (furopylene, phthene, pentene, hexene, heptene, etc.) whose content in the copolymer is about 15i% or less. Examples of ethylene polymers include block or random copolymers of ethylene and propylene, and among these, random or block copolymers of ethylene and propylene with an ethylene content of 2 to 15% by weight, or copolymers of this type. It is preferable to mix up to 50% by weight of an ethylene polymer having a density of 0.93 g/cm' or more, particularly up to 25% of hair oil.

In addition, polyolefin resin melt flowray) (M
FR) is 0.01-20g710min, especially 0.5-l
Preferably, the amount is Og/lo. A stabilizer or the like may be added to the polyolefin resin.

In addition, examples of unsaturated compounds having a polar group (hereinafter sometimes simply referred to as a modifier) include vinyltriethoxysilane, methacryloyloxytrimethoxysilane, γ-methacryloyloxypropyltrimethoxysilane, methacryloyloxypropyltrimethoxysilane, and methacryloyloxypropyltrimethoxysilane. Acryloyloxycyclohexyltrimethoxy.

Organic silane compounds such as γ-methacryloyloxypropyltriacetyloxysilane, methacryloyloxytriethoxysilane, γ-methacryloyloxypropyltriethoxysilane, allyl glycidyl ether, 2-methyl-allyl glycidyl ether,
Sodium acrylate, sodium methacrylate, calcium acrylate, calcium methacrylate.

Magnesium acrylate, Magnesium methacrylate, Zinc acrylate, Zinc methacrylate, Aluminum acrylate, Aluminum methacrylate,
Metal chloride compounds of (meth)acrylic acid such as iron acrylate (■), iron (III) methacrylate, and triallyl cyanurate.

Tri(2-methylallyl) cyanurate.

1.3.5-) lya-acryloyl hexahydro-8-triazine, 1,3.5-1 ly-methacryloyl hexahydro-s-triazine, 4-7 acryloyloxyphenol, 4-(acryloyloxymethyl)phenol, 4-7 chloroyloxybenzyl alcohol,
Examples include 4-methacryloyloxyphenol, 4-methacryloyloxybenzyl alcohol, and 4-(methacryloyloxymethyl)benzyl alcohol.

Among these, organic silane compounds are preferred, and the modifiers marked with # may be used alone or in combination of two or more.

Furthermore, the organic peroxide mentioned above is preferably one having a 1-minute half-life temperature of about 160 to 280°C, such as 1, for example, tert-butylperoxyisopropyl carbonate. , ditert-butylshiba
Oxyphthalate.

tert-butylperoxyacetate-1., 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane,
2,5-dimethyl-2,5-di(tert-butylperoxy)hexyne-3, tert-butylperoxylaurate,
Tertiary butyl peroxybenzoate, methyl ethyl ketone peroxide, dicumyl peroxide, cyclohexanone peroxide, tertiary butyl cumyl peroxide, 2.5-dimethylhexane = 2.5-
Examples include oxide robber oxide. These organic peroxides may be used alone or in combination of two or more.

The blending ratio of the polyolefin resin, modifier, and organic peroxide varies depending on the desired MFR of the modified polyolefin, but generally, the modifier is o, oi, based on 100 parts by weight of the polyolefin resin. ~5 parts by weight,
Particularly preferred is a range of 0.1 to 3 parts by weight, and a range of 0.01 to 5 parts by weight, especially 0.1 to 2 parts by weight of the organic peroxide.

In addition, the blending ratio of the modifier and organic peroxide is as follows: modifier 1
00 parts by weight, the organic peroxide is preferably in the range of 5 to 80 parts by weight.

The modified polyolefin used in this invention is prepared by mixing a polyolefin resin, a modifier, and an organic peroxide by a method known per se, preferably by applying a known suitable mixing method under conditions that the organic peroxide does not decompose. A temperature at which the polyolefin resin, a modifier, and an organic peroxide are mixed and the resulting mixture is melted but not decomposed.

Preferably about 180-260'0, especially 220-2
It is obtained by heating to a temperature of 50°C and reacting. The simplest heat treatment operation is to melt and heat the mixture in an extruder at the above temperature for about 2 to 5 minutes.

The modified polyolefin obtained in the above manner is MF
Modified polyolefins having an R of 1 to 150 g/10 min, particularly preferably 10 to 50 g/10 min, are usually formed into pellets.

The inorganic substance used in this invention is calcium carbonate (
(heavy, light) and talc are preferably used. The inorganic substance has an average particle size of 0.05 to 1oIL, especially 0.5 to 5
g, a powder with a specific surface area of 0.1 to 100 square meters/g, particularly preferably 1 to 30 square meters/g,
Preferably, the inorganic substance is not surface-treated.

Furthermore, examples of the unmodified polyolefin resin used in this invention include the polyolefin resins described above. The MFR of unmodified polyolefin resin is o, i ~ 10g/1
0 min, especially 0.3 to 5 g/10 min is preferred, and the same type of olefin as used to obtain the modified polyolefin is preferably used for the olefin.

In particular, the above-mentioned crystalline propylene polymer is preferably used as the unmodified polyolefin resin.

Conventionally known additives (
Antioxidants, ultraviolet absorbers, etc.) may be added.

The powdered inorganic substance and modified polyolefin may each be used in the form of a master batch of unmodified polyolefin resin.

The adhesive polyolefin composition of the present invention comprises a modified polyolefin, a powdery inorganic substance, and an unmodified polyolefin resin, in which the proportions of each component in one composition are (a): 10 to 80% by weight of modified polyolefin; It can be obtained by mixing b): 5 to 50% by weight of a powdered inorganic substance, preferably 10 to 50% by weight, and (c): 10 to 80% by weight of an unmodified polyolefin resin. During mixing, various additives such as weathering (thermal) stabilizers, molding aids, etc. may be added.

The simplest mixing operation is to mix each of the above components at approximately 180-260%
C., particularly 220 to 250.degree. C., for about 1 to 10 minutes in an extruder.

Examples of the extruder include a single-screw or twin-screw extruder and a continuous mixer such as FCM.

The effect of the present invention is further improved by performing a degassing operation (venting) during melt-mixing. This is because there is moisture attached to the surface of the powdered inorganic substance.

The composition in this invention comprises (a), (b) and (c)
) by mixing each component in the specific proportions,
Compared to conventionally known polyolefin resin adhesives,
It has high adhesive strength to thin metal plates, exhibits extremely excellent properties as a sealing material, and can yield thin batteries with good long-term storage characteristics. If the blending ratio of each component in the composition is outside the above range, a composition with high adhesive strength cannot be obtained.

The method for obtaining a thin battery using the above composition as a sealing material is not particularly limited. For example, it may be formed into a sheet or film, and then used as a window frame sheet member with a positive electrode inside. l! A thin battery with excellent sealing performance can be obtained by sandwiching the solute diaphragm and the negative electrode between the peripheral edges of a pair of laminated thin metal exterior plates and bonding them under heat. Also,
The sheet or film can also be used as a three-layer sheet or a three-layer film in which the composition of the present invention is used as an adhesive layer and one layer of unmodified resin is provided in the middle.

[Example of the present invention] Next, examples and comparative examples will be shown.

In the following description, parts refer to weight fffl, and melt flow rate (MFR) was measured according to ASTM D 1 238. In addition, long-term storage stability was determined by a constant current discharge test at 200 lA after being left for 60 days after manufacture.

(Example 1) (Method for creating a sealing material sheet) Ethylene-propylene block copolymer (MFRI,
Og/10 min, ethylene content 8% by weight, melting temperature approx. 16
Ir as an antioxidant was added to 100 parts of powder of 0″C).
Zanox 1010 (Musashino Geigy) 0.1 part, Antiox S (NOF) 0.2 part, calcium stearate 0.05 part, γ-methacryloyloxypropyltrimethoxysilane as a modifier 0.5 part, and organic filtrate. 0.25 parts of tert-butylperoxybenzony (as the oxide) was mixed for 10 minutes using a Henschel mixer, and then mixed at 240°C for 2 minutes using a 50 mmφ-axial extruder (
Residence time) The mixture was melted and heated for reaction to obtain modified polypropylene pellets of approximately 2 mmφ x 3 mm and an MFR of 22 g/10 minutes.

This pellet and calcium carbonate (White SSB red,
Average particle size 1.25IL, specific surface area 1.85 square meters/g, Shiraishi calcium) (hereinafter abbreviated as Charcoal a) and ethylene-propylene block copolymer (MFRl,
0g710min, ethylene content 8% by weight, melting temperature 160
℃) (hereinafter sometimes abbreviated as Polypro A) (containing a known antioxidant, calcium stearate) are blended in the proportions shown in Table 1, mixed in a blender, and then - Thickness: 200 pm using a screw extruder
A sheet of adhesive polyolefin composition was obtained.

From this sheet, a circular sealing material sheet having an outer diameter of 40 mm x 40 mm and a width of 4 mm was created using a punching blade.

(Creation method of positive electrode mixture) Manganese dioxide 332.9 mg, acetylene black 6
2.4 mg of the mixture, methoxypolyethylene glycol monoacrylate (AM-90G manufactured by Shin Nakamura Chemical) 31
．． 4mg, polyethylene glycol dimethacrylate (
Lithium perchlorate was dissolved in dimethoxybolyethylene glycol (Asahi Denka LX'-521) (concentration 0, 75 mmol/f).
62.8 mg of the solution of L) and 0.067 mg of benzoyl peroxide were further mixed to prepare a positive electrode mixture.

(Creation method of positive electrode) - As a negative electrode current collector and exterior plate, the dimensions are 40 x 40 x 0.0
Place the above positive electrode mixture on a 5mm stainless steel foil in a size of 28x28.
It was applied uniformly to a size of mm.

This was pressure-molded and heated at 100°C for 3 hours to form a positive electrode plate (
A positive electrode laminate A consisting of a 300 parts (thickness of 300 parts m) and an exterior plate was prepared.

(Method for creating negative electrode and electrolyte diaphragm) As a negative electrode current collector and exterior plate, the dimensions are 40 x 40 x 0.0.
One dimension is 26 x 26 x 0.07 on 5 mm stainless steel foil.
A piece of lithium foil with a thickness of mm was crimped.

18.4 mg of AM-90G as an electrolyte composition
, 6.0 mg of 9G, lithium perchlorate LX-521
A solution (concentration 0, 75 mol/JL) dissolved in
A mixed solution containing 5.6 mg of 2,2-dimethoxyacetophenone and 0.1 mg of 2,2-dimethoxyacetophenone as a photosensitizer was prepared. Applying 8 ml of this electrolyte solution to the lithium metal disk,
Using a 250 W ultra-high pressure mercury lamp, irradiation was performed for 3 minutes at an illuminance of 5 mW/cm to form a cured film with a thickness of 50 JLm, thereby creating a laminate B of the current collector/exterior plate, the negative electrode, and the electrolyte partition 11Q.

(Battery assembly) The above laminates A and B were stacked, the annular sealing sheet was sandwiched between the outer periphery of the outer plate, and heat and pressure bonded (180°C, 3
K g/cm'', 3 minutes), and the thin battery ■ was assembled.

The results of the battery discharge test are shown in FIG. 1 below.

(Example 2) A thin battery (2) was assembled in the same manner as in Example 1, except that the components of the composition were blended in the proportions shown in Table 1.

(Example 3) Calcium carbonate (Whiten SB,
Average particle size 2.2IL, specific surface ml, 05rn'/g
, Shiraishi calcium) (hereinafter abbreviated as Charcoal b), and in place of polypro A, an ethylene-propylene block copolymer (MFRo, 35gyxo content, ethylene content 6) was used.
% by weight, melting temperature 158°C) (hereinafter abbreviated as Polypro B4), and except that each component was blended in the proportions shown in Table 1, the same procedure as in Example 1 was carried out to produce a thin battery. Assembled.

(Comparative Example 1) A thin battery (2) was assembled in the same manner as in Example 1, except that calcium carbonate was not blended and other components were blended in the proportions shown in Table 1.

(Comparative Example 2) Other components were added to the first layer without adding unmodified polypropylene.
A thin battery (2) was assembled in the same manner as in Example 1 except that the ingredients were mixed in the proportions shown in the table.

(Margin below) Table 1

[Brief explanation of the drawing]

FIG. 1 is a characteristic diagram showing the results of a battery discharge test of the thin battery according to the present invention, and ■ is a characteristic diagram showing the results of a battery discharge test of the thin battery according to the present invention.
indicates the thin battery according to Example 2, ■ indicates the thin battery according to Example 3, ■ indicates the thin battery according to Comparative Example 1, and ■ indicates Comparative Example 2.
of thin batteries. These are the results of a constant current discharge test of 200 pA.

Claims (4)

[Claims] (1) A separator containing an electrolyte or a solid electrolyte diaphragm is formed between the positive electrode and the negative electrode inside an exterior plate consisting of a pair of opposing thin metal plates that also serves as a current collector, and the periphery of the exterior plate is covered with a sealing material. A thin battery sealed with a thin battery, characterized in that the sealing material consists of each of the following components (a) to (c). (a) is 10 to 80% by weight, (b) is 5 to 50% by weight,
An adhesive polyolefin composition characterized in that (c) is 10 to 80% by weight. (a) Modified polyolefin obtained by heating a polyolefin resin and an unsaturated compound having a polar group in the presence of an organic peroxide (b) Powdered inorganic substance (c) Unmodified polyolefin resin (2) The thin battery according to claim 1, wherein the unsaturated compound having a polar group is an organic silane compound. (3) The thin battery according to claim 1, wherein the powdered inorganic substance is calcium carbonate. (4) The thin battery according to claim 1, wherein the polyolefin resin is a crystalline propylene polymer.