JPH0451941B2 - - Google Patents

Description

Detailed Description of the Invention [Industrial Technical Field] The present invention is a sealing material that has particularly excellent adhesion and bending properties, and is heat shock resistant, for sealing the peripheral edge of an exterior plate that also serves as a current collector for both positive and negative electrodes. The present invention relates to a thin battery with excellent long-term storage stability, which is characterized by being sealed with a sealing material having properties. [Technical background of the invention and its problems] Recently, as electronic devices have become smaller and thinner, batteries as a power source for these devices have also become smaller and thinner.
There is a strong demand for smaller size and thinner film. In particular, so-called sheet batteries and paper batteries, which are 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. These thin batteries. A structure has been proposed in which the periphery of a flat plate-shaped exterior plate for both positive and negative electrodes, which also serves as a current collector, is sealed with a thermal adhesive resin. This thermoadhesive resin is required to have the following properties. In other words, as the thickness of the positive and negative electrodes decreases, the insulation between the two electrodes is maintained sufficiently, and the sealing performance is good and there is no electrolyte leakage.
A sealing material with excellent long-term storage is required. Furthermore, from the viewpoint of high energy density, a so-called non-aqueous electrolyte lithium battery type thin-film battery has been developed, using lithium as the negative electrode active material and a non-aqueous electrolyte containing an inorganic salt dissolved in an organic solvent as the electrolyte. It is actively practiced. In this 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, fluorocarbon resins, and modified products thereof have been proposed as heat-adhesive resins that satisfy these characteristics. , 60
-148050, 60-160559, 60-185359,
60-185360, 60-220553, 61-68860
No. 61-185867, No. 61-74256, No. 61-
No. 176054 and No. 61-185867 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, these modified products do not necessarily have sufficient adhesion to satisfy the above-mentioned required properties as a sealing material, and batteries using these as a sealing material have problems with long-term reliability. ,
There is a need for a sealing material that has even better adhesion, bending properties, and heat shock resistance. Therefore, various improvement methods have been proposed in order to impart adhesive properties to polyolefin resins. One method is to improve the adhesiveness of polyolefin resin by modifying it with a type of modifier selected from γ-methacryloyloxypropyl trimexysilane, glycidyl methacrylate, etc. and an organic peroxide. Proposed.
However, the improvement in adhesion of modified polyolefins obtained by this method is still not satisfactory. In addition, thin batteries require good bending properties, and the sealing material must maintain adhesion to the exterior plate after a bending test and must not cause cracks. Modified polyolefins obtained by the conventional methods described above are insufficient in these properties. Therefore, an object of the present invention is to provide a sealing material that improves the shortcomings of conventional thin batteries, and that has particularly excellent adhesion and bending properties, and also provides long-term stability using a sealing material that also has heat shock resistance. Our goal is to provide an excellent thin battery. [Means for solving the problem] The present invention includes a separator containing an electrolyte or a solid electrolyte diaphragm between a positive electrode and a negative electrode inside an exterior plate consisting of a pair of opposing thin metal plates that also serves as a current collector. The battery is a thin battery in which the periphery of the exterior plate is sealed with a sealing material, and the sealing material contains at least three of the following components (a) to (e). The blending proportions are 10 to 95% by weight of (a), 0 to 85% by weight of (b), and 5 to 60% by weight of (c) in the total weight of the polymer, and (a) and (b) in the total composition weight. ) and (c) total 50-90
Weight%, (d) 5 to 50% by weight, (e) 0 to 45% by weight,
A thin battery characterized by using an adhesive polyolefin composition in which the total amount of (d) and (e) is 10 to 50% by weight. (a) Modified polyolefin obtained by grafting polyolefin with an organosilane compound having an ethylenically unsaturated bond (b) Unmodified polyolefin (c) Elastomer (d) Calcium carbonate (e) Inorganic substances other than calcium carbonate By providing this, the above objective has been achieved. Each component of the encapsulant composition used in the thin battery of the present invention will be explained in detail. The modified polyolefin (a) used in the present invention is obtained by grafting polyolefin with an organic silane compound having an ethylenically unsaturated bond or an unsaturated compound having a polar group, preferably in the presence of an organic peroxide. . Examples of the polyolefins include crystalline homopolymers of propylene, binary or more block or random copolymers of propylene and other α-olefins (e.g., ethylene, butene, pentene, hexene, heptene, etc.), and dienes. Ethylene polymers such as propylene polymers, ethylene homopolymers, binary or more block or random copolymers of ethylene and α-olefins (propylene, butene, pentene, hexene, heptene, etc.), and dienes. can be mentioned. Examples of the organic silane compound having an ethylenically unsaturated bond include vinyltriethoxysilane,
Methacryloyloxytrimethoxysilane, γ
-methacryloyloxypropyltrimethoxysilane, methacryloxycyclohexyltrimethoxysilane, γ-methacryloyloxypropyltriacetyloxysilane, methacryloyloxytriethoxysilane, γ-methacryloyloxypropyltriethoxysilane, and the like. In addition, as unsaturated compounds having polar groups,
Allyl glycidyl ether, 2-methyl-allyl glycidyl ether, sodium acrylate, sodium methacrylate, calcium acrylate, calcium methacrylate, magnesium acrylate, magnesium methacrylate, zinc acrylate, zinc methacrylate, acrylic acid Metal salt compounds of (meth)acrylic acid such as aluminum, aluminum methacrylate, iron acrylate (), iron methacrylate (), triallyl cyanurate, tri(2-methylallyl) cyanurate, 1,3,5- triacryloylhexahydro-s-triazine, 1,3,5-trimethacryloylhexahydro-s-triazine, 4-
Examples include acryloyloxyphenol, 4-(acryloyloxymethyl)phenol, 4-acryloyloxybenzyl alcohol, 4-methacryloyloxyphenol, 4-methacryloyloxybenzyl alcohol, 4-(methacryloyloxymethyl)benzyl alcohol, and the like. Among these, organic silane compounds are preferred. The above-mentioned modifier (organosilane compound or unsaturated compound having a polar group) may be used alone or in combination of two or more. Further, as the above-mentioned organic peroxide, it is preferable to use one having a half-life temperature of about 160 to 260°C, such as tert-butylperoxyisopropyl carbonate, di-tert-butylperoxyisopropyl carbonate, etc. Butyl diperoxyphthalate, tert-butyl peroxyacetate, 2,5-dimethyl-2,
5-di(tert-butylperoxy)hexane, 2,
5-dimethyl-2,5-di(tert-butylperoxy)hexyne-3, tert-butyl peroxylaurate, tert-butyl peroxymale acid, tert-butyl peroxybenzoate, methyl ethyl ketone peroxide, dichloromethane Mil peroxide, cyclohexanone peroxide, tert-butyl cumyl peroxide, 2,5-dimethylhexane-2,5-dihalide droproxide, and the like. These organic peroxides are 1
Only the seeds may be used, or two or more types may be used in combination. The blending ratio of the above-mentioned polyolefin resin, modifier, and organic peroxide varies depending on the desired MFR (melt flow rate index) of the modified polyolefin, but in general, it is added to 100 parts by weight of the polyolefin resin. On the other hand, the modifier is 0.01~5
Parts by weight, especially 0.1 to 3 parts by weight, of organic peroxide
A range of 0.01 to 5 parts by weight, particularly 0.1 to 2 parts by weight is preferred. In addition, the blending ratio of the modifier and organic peroxide is
5 to 80 parts of organic peroxide per 100 parts by weight of modifier
Parts by weight ranges are preferred. The modified polyolefin used in the present invention is prepared by mixing a polyolefin resin, a modifier, and an organic peroxide by a method known per se, preferably under conditions that do not decompose the organic peroxide. The polyolefin resin, the modifier and the organic peroxide are mixed by applying the direction, and the resulting mixture is heated to a temperature at which the polyolefin resin melts but does not decompose, preferably about 180-260°C, especially 220-250°C. It is obtained by heating to a certain temperature and causing a graft reaction. 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. Further, the graft reaction may be carried out in an organic solvent. Furthermore, examples of the unmodified polyolefin resin (b) used in this invention include the polyolefin resins described above. In particular, the same type as that used to obtain the modified polyolefin is preferably used. 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 blended with the unmodified polyolefin resin. calcium carbonate, inorganic matter,
Each modified polyolefin may be used in the form of a masterbatch of unmodified polyolefin resin. The elastomer (c) used in the present invention includes:
A polymer having a lower tensile modulus (ASTMD-882-73) at room temperature than modified or unmodified polyolefin polymers is used. Specifically, various polyethylenes, ethylene/propylene, ethylene/propylene/diene, ethylene/acrylic acid, ethylene/butene, ethylene/ethyl acrylate, ionomers, ethylene vinyl acetate, styrene/butadiene copolymers, and liquid rubbers. , and derivatives such as unsaturated acids, acid esters, metal salts, imides, amides, and unsaturated silane compounds that are addition-modified or partially crosslinked can also be used. Among these, ethylene/propylene/(diene) rubber or modified products thereof are preferred for crystalline polypropylene. In addition, when using this unmodified elastomer, polyamide, polyester ether amide, polyester amide, polyether amide, etc. which are compatible with this elastomer can be used. Calcium carbonate (heavy, light) used in the present invention
(d) is preferably a powder having an average particle diameter of 0.05 to 10 μm, particularly 0.5 to 5 μm, and a specific surface area of 0.1 to 100 m ² /g, especially 1 to 30 m ² /g. Preferably, calcium carbonate is not surface-treated. Inorganic substances (e) other than calcium carbonate used in the present invention include metals such as talc, mica, carbon black, metal powder, carbon fiber, silicon oxide, silicon carbonates, hydroxides, oxides, etc. It also includes processed and transformed fibrous materials. These inorganic substances are not effective in improving adhesion but are effective in damping vibration. In the adhesive polyolefin composition of the present invention, the blending ratio of each of the above components is (a): 10 to 95% by weight of modified polyolefin, (b): 0 to 85% by weight of unmodified polyolefin, preferably 10% by weight of unmodified polyolefin. -85% by weight, (c): 5-60% by weight of elastomer, 50-90% by weight of the total of (a), (b) and (c) in the total composition weight, (d): 5-90% by weight of calcium carbonate. 50% by weight, (e): 0 to 45% by weight of inorganic substances excluding calcium carbonate, the total of (d) and (e) is 10
It can be obtained by mixing so that the amount becomes ~50% by weight. If the ratio of each component is outside the above range, the adhesiveness, heat resistance, or vibration damping properties of the resulting composition will decrease. If the ratio of (a) is outside the above range, the adhesion will decrease,
If the proportion of (b) is more than 85% by weight, the adhesion will decrease,
If the proportion of (c) is less than 5% by weight, the composition will become hard and the heat shockability and adhesiveness will decrease.
Moreover, if it is more than 60% by weight, the composition becomes soft and adhesiveness and heat resistance decrease. The proportion of (d) is 5% by weight
If the amount is less, adhesiveness and strength will decrease. Also,
If it is more than 50% by weight, it will have the disadvantage of becoming brittle. The adhesive polyolefin composition of the present invention may contain various additives, such as weathering (thermal) stabilizers, molding aids, etc., at the time of mixing each component. The simplest mixing operation is to melt-mix the above-mentioned components in an extruder at a temperature of about 180 to 260°C, particularly 220 to 250°C, for about 1 to 10 minutes. 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 deaeration operation (venting) during melt-mixing. This is because there is moisture attached to the surface of the powdered inorganic substance. By mixing each of the components (a) to (e) in the above-mentioned specific ratios, the composition of the present invention has a greater adhesive strength for thin metal sheets than conventionally known polyolefin resin-based adhesives. It has adhesive strength and exhibits extremely excellent properties as a sealing material, making it possible to obtain a thin battery with good long-term storage characteristics. If the blending ratio of each component in the composition is outside the above range, it will not be possible to obtain a composition that has adhesive properties, bending properties, and heat shock resistance. There are no particular limitations on the method for obtaining a thin battery using the above composition as a sealing material. A thin battery with excellent sealing performance can be obtained by sandwiching the laminate between the peripheral edges of a pair of laminated thin metal exterior plates and bonding them under heat. Further, the sheet or film described above 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 an intermediate layer made of an unmodified resin is provided in the middle. [Examples of the present invention] Next, Examples and Comparative Examples will be shown. In the following description, parts indicate parts by weight, and melt flow rate (MFR) was measured according to ASTM D1238. In addition, long-term storage stability was determined by a constant current discharge test at 200 μA after being left for 60 days after manufacture. The bending property test was conducted according to the IC card bending strength measurement method (DP7816/1). That is, the movable part was repeatedly moved left and right so that the amount of deflection as shown in FIG. 1 was 0 to 3 mm. The adhesive compositions of Examples and Comparative Examples are collectively shown in Table 1. [Example 1] (Method for creating a sealant sheet) Ethylene-propylene block copolymer (MER, 1.0 g/10 min, ethylene content 3% by weight,
Irganox 1010 as an antioxidant is added to 100 parts of powder with a melting temperature of approximately 160℃ and a tensile modulus of 14200Kg/ ^m2 ).
(Musashino Geigy) 0.1 part and Antiox S
(NOF) 0.2 parts, calcium stearate 0.05
1 part, 0.5 parts of γ-methacryloyloxypropyltrimethoxysilane as a modifier and tert-butyl peroxybenzoate as an organic peroxide.
Mix 0.25 parts with a Henschel mixer for 10 minutes, melt and heat at 240°C for 2 minutes (residence time) in a 50 mmφ single screw extruder to react, and make a modified polypropylene of about 2 mmφ x 3 mm with an MFR of 22 g/10 minutes. Got pellets. This pellet and calcium carbonate (White SSB red, average particle size 1.25μ, specific surface area
Pellets ( ^{known oxidation} inhibitor,
(contains calcium stearate) and ethylene-propylene copolymer rubber (Japan Synthetic Rubber)
Co., Ltd., EP-02P, tensile modulus 80Kg/cm ² ]
After blending in the proportions shown in the table and mixing in a blender, they were melt-kneaded for 2 minutes at 250°C in a 50 mmφ vented single screw extruder to obtain adhesive polyolefin composition pellets of approximately 2 mmφ×3 mm. An adhesive polyolefin sheet was prepared from this. From this sheet, with a punch blade, the outer diameter is 40 x 40 mm.
A circular sealant sheet with a width of 4 mm was prepared. (Creation method of positive electrode mixture) Manganese dioxide 332.9 mg, acetylene black
Methoxypolyethylene glycol monoacrylate (AM-
90G) 31.4mg, polyethylene glycol dimethacrylate (Shin Nakamura Chemical 9G) 10.7mg, dimethoxypolyethylene glycol (Asahi Denka LX-521)
Lithium perchlorate was dissolved in (concentration 0.75 m
mol/) solution and 0.067 mg of benzoyl peroxide were further mixed to prepare a positive electrode mixture. (Creation method of positive electrode) As a positive electrode current collector and exterior plate, the dimensions are 40 x 40 x
Spread the above positive electrode mixture 28x on 0.05mm stainless steel foil.
It was applied uniformly to a size of 28 mm. This was pressure-molded and heated at 100° C. for 3 hours to create a positive electrode laminate A consisting of a positive electrode plate (300 μm thick) and an exterior plate. (Method for creating negative electrode and electrolyte diaphragm) As a negative electrode current collector and exterior plate, the dimensions are 40 x 40 x
Dimensions are 26 x 26 x 0.07 mm on 0.05 mm stainless steel foil.
lithium foil was crimped. As a composition for electrolyte, 18.4 mg of AM-90G,
6.0 mg of 9G, 25.6 mg of a solution (concentration 0.75 mol/) of lithium perchlorate dissolved in LX-521, and
A mixed solution containing 0.1 mg of 2,2-dimethoxyacetophenone as a photosensitizer was prepared. This electrolyte solution
8 μm was applied to the lithium metal disk and irradiated for 3 minutes at an illumination intensity of 5 mW/cm using a 250 W ultra-high pressure mercury lamp to form a cured film with a thickness of 50 μm.
A laminate B including a current collector/exterior plate, a negative electrode, and an electrolyte diaphragm was created. (Assembling the battery) The above laminates A and B are stacked, the annular sealing sheet is sandwiched between the outer periphery of the outer plate, and heat and pressure bonded (180°C, 3Kg/cm ² , 3 minutes) to form a thin battery. assembled. The results of the battery discharge test are shown in FIG. 2 below. In addition, regarding the battery, bending test
Even after 5,000 cycles, no abnormality was observed in the sealing part or electrical properties. [Example 2] Polyethylene was used instead of EPR in Example 1 [manufactured by Ube Industries, Ltd., F222, tensile modulus 1200 Kg/cm ² ]
A thin battery was assembled in the same manner as in Example 1 except that (PE) was used. Note that the bending test results for the battery were the same as in Example 1. [Example 3] A thin battery was assembled in the same manner as in Example 2, except that unmodified polypropylene was not used and talc was used as the inorganic substance. Note that the bending test results for the battery were the same as in Example 1. [Example 4] Ethylene/propylene/diene copolymer [manufactured by Japan Synthetic Rubber Co., Ltd.] was used instead of EPR in Example 1.
A thin battery was assembled in the same manner as in Example 2, except that EP57P with a tensile modulus of elasticity of 80 Kg/cm ² (EPDM) was used. Note that the bending test results for the battery were the same as in Example 1. [Comparative Example 1] A thin battery was assembled in the same manner as in Example 1, except that unmodified polypropylene was used instead of modified polypropylene. When the battery was subjected to a bending test, peeling was observed at the sealing part after 1200 cycles. 【table】

[Brief explanation of the drawing]

FIG. 1 shows a method for testing bending characteristics in the present invention. FIG. 2 is a characteristic diagram showing the results of a battery discharge test of the thin battery according to the present invention, where is the thin battery according to Example 1, is the thin battery according to Example 2, and is the thin battery according to Example 3. 200 μA constant current discharge test results for the thin battery according to Example 4 and the thin battery according to Comparative Example 1, respectively.

Claims (1)

[Claims] 1. A separator containing an electrolyte or a solid electrolyte diaphragm is formed between a positive electrode and a negative electrode inside an exterior plate consisting of a pair of opposing thin metal plates that also serves as a current collector, and A thin battery whose periphery is sealed with a sealing material, the sealing material containing at least three of the following components (a) to (e),
The blending ratio of each component is 10 to 95 (a) in the polymer weight.
% by weight, (b) is 0 to 85% by weight, (c) is 5 to 60% by weight, and the total of (a), (b), and (c) in the total composition weight is 50 to 85% by weight.
Use an adhesive polyolefin composition in which (d) is 5 to 50 weight %, (e) is 0 to 45 weight %, and the total of (d) and (e) is 10 to 50 weight %. A thin battery featuring (a) Modified polyolefin obtained by grafting polyolefin with an organosilane compound having an ethylenically unsaturated bond (b) Unmodified polyolefin (c) Elastomer (d) Calcium carbonate (e) Inorganic substances other than calcium carbonate