JPH1055789A - Sealant for organic electrolyte battery, composition containing the same, and battery using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a battery with its superior sealing property at high temperature and superior operability by employing a sealant for organic electrolyte mainly containing dien rubber of which average molecule weight is a value with a specific range. SOLUTION: A specified amount of sealant composition is fed and applied onto a metal container surface and/or insulation material gasket surface by a metering pump such as fixed quantity dispenser air-driven, roller pump, and gear pump. Then, these applied materials are naturally dried so that the sealing compound is maintained to be horizontal without being one-sided, an organic solvent is removed, and dien rubber film is formed. It is possible to apply a small amount of this composition by employing a brush without limitation to a method using the metering pump. the thickness of the sealant layer can be arbitrarily selected according to size of the metal container and insulation gasket, and the size is usually 0.1 to 1,000 micrometers. Thus, a sealant for organic electrolyte battery with its superior sealing property at high temperature can be obtained in particular.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sealant which is used in an organic electrolyte battery and has a particularly excellent sealing property at a high temperature.

[0002]

2. Description of the Related Art The size and weight of acid / lead batteries and nickel / cadmium batteries which have been widely used as secondary batteries until now have become smaller as electric appliances have been miniaturized. In recent years, it has been proposed to use an organic electrolyte battery that is small, lightweight, capable of high output and high energy density as a secondary battery, and lithium secondary batteries or lithium ion secondary batteries are currently the mainstream. Has become. In this organic electrolyte battery, the power generating element is housed in a metal container and sealed. The power generating element is an electrolytic solution composed of a supporting electrolyte and an organic electrolytic solution solvent, active materials for a positive electrode and a negative electrode, a separator, and the like. The supporting electrolyte constituting the electrolytic solution is, for example, LiPF ₆ , LiBF ₄ , LiC
Water reacts with hydrolysable compounds such as lithium compounds such as lO ₄ is used. As the organic electrolyte solvent, for example, flammable organic compounds such as propylene carbonate, ethylene carbonate, and diethyl carbonate are used. When water enters such a battery, battery performance such as cycle characteristics is significantly deteriorated. This prevents water from entering the battery,
In addition, it is necessary to prevent electrolyte leakage, and these batteries are required to have high hermeticity. By the way, an organic electrolyte battery has its power generating element housed in a metal container for hermetic sealing, but it is necessary to insulate between a positive electrode terminal and a negative electrode terminal in order to prevent a short circuit between the positive electrode and the negative electrode. Usually, a gasket made of an insulating material is used in an opening of a metal container containing a power generation element for insulation and sealing between the positive and negative electrodes. It is known that a resin insulating gasket is used as an insulating material (Japanese Patent Publication No. 57-45028).
JP, JP-A-59-205153, and the like. As resin materials, polyethylene (JP-A-59-205153, etc.), fluororesin (JP-A-59-205152, etc.), an elastic modulus of 12,
Polyolefin resins of 000 to 18,000 Kg / cm ² (JP-A-7-130341 and the like) are known.

In order to further enhance the sealing by such an insulating gasket, it has been proposed to use an insulating gasket and a sealant together (Japanese Patent Application Laid-Open No. 55-030148).
JP, JP-A-55-016352, JP-A-59-016352
-11565 publication). The sealing agent is applied to an insulating gasket or a metal container, and the insulating gasket is mounted on the metal container, thereby enhancing the sealing between the insulating gasket and the metal container. As such a sealant,
Pitch-based materials such as coal tar and asphalt, and materials obtained by adding a polymer to a pitch-based material as a modifier (JP-A-56-032671, JP-A-58-010365)
JP, JP-A-59-091660, JP-A-6-09660
No. 124694, JP-A-6-005270 and the like. In addition to pitch-based materials, butyl rubber (JP-A-55-03148) and polyolefin-based adhesives (JP-A-56-032672). Publication), polyvinylidene fluoride resin (Japanese Patent Laid-Open No. 1404/1990)
No. 69, etc.) have been proposed. However, these sealants are apt to deteriorate under high temperature conditions, and batteries that are to be mounted more widely in electric appliances and the like are required to have higher temperature stability.

[0004]

Based on such prior art, the present inventors have conducted intensive studies to obtain a sealant for an organic electrolyte battery which is stable even at high temperatures. The inventors have found that the present invention has excellent sealing properties and excellent operability, and has completed the present invention.

[0005]

According to the present invention, the weight average molecular weight is from 10,000 to 1,500,000.
The present invention provides a sealant for an organic electrolyte battery containing a diene rubber of 0 as a main component, and the sealant has 5 to 15 carbon atoms.
And a sealing agent composition dissolved in an organic solvent of (a), wherein the sealing agent is provided between an insulating gasket and a metal container attached to an opening of a metal container (hereinafter, simply referred to as a metal container) housing a power generation element. The present invention provides an organic electrolyte battery used between the insulating gasket and the sealing body.

Hereinafter, the present invention will be described in detail. (Sealant) The sealant of the present invention has a weight average molecular weight of 1
000 to 1,500,000, preferably 20,000
00 to 800,000, more preferably 50,000 to
It has 700,000 diene rubber as a main component. When the weight average molecular weight exceeds 1,500,000,
When a diene rubber is dissolved in an organic solvent to form a sealant composition, the viscosity becomes too high, and it becomes difficult to control the thickness of the sealant layer when applied to an insulating gasket. If it is less than 10,000, the strength as a sealant is weak, and when the insulating gasket is mounted, a crack is formed in the sealant layer, and the sealing effect is deteriorated. If the content of the cis body is less than 30%, it is necessary to pay attention to the fact that the rebound resilience is reduced, and the insulating gasket may be deformed and cracked when the gasket is attached. The diene rubber as a main component of the sealant of the present invention is a homopolymer of a diene monomer, a copolymer of two or more diene monomers, or a copolymer of a diene monomer and a non-polar polymerizable monomer. However, in a copolymer of a diene monomer and a non-polar polymerizable monomer, the proportion of the non-polar polymerizable monomer is usually 300% by weight or less, preferably not more than 300% by weight based on the total amount of the diene monomer. Used at 100% by weight or less. Examples of the diene monomer which is a raw material of the diene rubber include butadiene, isoprene, piperylene, and 1,3-pentadiene, and specific examples of the nonpolar polymerizable monomer include styrene, ethylene, propylene, and isobutylene. You. These monomers are reacted by a conventional method, for example, solution polymerization, coordination polymerization, emulsion polymerization, or the like, to obtain a diene rubber which is a main component of the sealant in the present invention. However, with respect to rubber obtained by using soap or the like as an emulsifier in emulsion polymerization, it is preferable that these are removed by washing. Such diene rubbers include butadiene rubber, isoprene rubber, piperylene rubber, 1,3-
Examples include pentadiene rubber, butadiene-isoprene rubber, styrene-butadiene rubber, isobutylene-isoprene rubber, and ethylene-propylene-diene monomer (such as butadiene) rubber. The cis-form content of the diene rubber is preferably 30% or more, more preferably 50% or more.
% Or more, more preferably 80% or more. A higher cis content is preferred because a sealant having good sealing properties tends to be obtained. Also, since the sealant of the present invention is often in contact with the electrolyte,
As a property of the sealant, resistance to insolubility / inactivity in the electrolyte and swelling is required. Further, the sealant of the present invention
Additives commonly used in rubber, such as an antioxidant, an ultraviolet absorber, and a coloring agent, which do not deteriorate the performance of the insulating gasket and do not react with or dissolve in the electrolytic solution, can be added.

(Sealant composition) The sealant composition of the present invention is obtained by dissolving the above-mentioned diene rubber in an organic solvent. This composition is applied to a metal container or an insulating gasket and dried. It becomes a seal that enhances the sealing performance with the metal container. The organic solvent used here is preferably an organic solvent having usually 5 to 15 carbon atoms, in which the above-mentioned diene rubber can be dissolved, and more preferably a hydrocarbon solvent having 6 to 12 carbon atoms, a nitrogen-containing organic solvent, or a nitrogen-containing organic solvent. Preferred examples thereof include an oxygen-based organic solvent, particularly an aromatic hydrocarbon-based solvent such as benzene, toluene, and xylene, and a saturated hydrocarbon-based solvent such as n-hexane, cyclohexane, methylcyclohexane, and ethylcyclohexane. Organic solvents having 5 or less carbon atoms, particularly 1 to 2 carbon atoms, such as carbon tetrachloride, are not preferred. The ratio of the diene rubber in the sealant composition of the present invention is from 1% by weight to 50% by weight, preferably from 2% by weight to 40% by weight, more preferably from 5% by weight to the organic solvent.
30% by weight. If the concentration of the diene rubber exceeds 50% by weight, the viscosity of the composition tends to be high, and the applicability tends to decrease. Conversely, when the concentration is less than 1% by weight, the amount of the solvent in the composition is too large, and the sealability tends to be poor. Further, an additive such as a coloring agent can be added to the sealant composition of the present invention as needed. It is desirable that the colorant that can be added does not react with the electrolytic solution and does not dissolve in the electrolytic solution, and examples thereof include various organic and inorganic pigments. Among them, carbon black, especially furnace black, channel black, etc.
Carbon black of 1 μm or less is preferred. When such a coloring agent is added, it is necessary to dissolve or disperse it sufficiently uniformly in the composition, and when using a granulated or aggregated one, a ball mill, sand mill, ultrasonic wave, etc. It is good to disperse with. The amount of such an additive such as a coloring agent may be any amount as necessary, but is usually 0.01 to 20% by weight, preferably 0.01 to 5% by weight based on the diene rubber. %, More preferably from 0.02% to 3% by weight. If the amount of the additive exceeds 20% by weight, the flexibility of the sealant is reduced, which may cause cracking.

(Organic Electrolyte Battery) The organic electrolyte battery of the present invention may be any organic electrolyte battery provided with the above-described sealant layer of the present invention between a metal container and an insulating gasket. The material of the metal container, the power generation element, and the insulating gasket may be those commonly used. In this organic electrolyte battery, the power generating element is housed in a metal container and sealed. The power generating element is an electrolytic solution composed of a supporting electrolyte and an organic electrolytic solution solvent, active materials for a positive electrode and a negative electrode, a separator, and the like. The supporting electrolyte constituting the electrolytic solution is, for example, LiPF ₆ , LiBF ₄ , LiClO
Compounds that readily react with water and hydrolyze, such as lithium compounds such as ₄ , are used. As the organic electrolyte solvent, for example, flammable organic compounds such as propylene carbonate, ethylene carbonate, and diethyl carbonate are used. As an insulating gasket, polyethylene, which is generally said to have high electrolyte resistance,
It is preferable to use polyolefin resins such as polypropylene and ethylene copolymerized polypropylene, and particularly ethylene copolymerized polypropylene because of its good balance between strength and elastic modulus. Furthermore, polyolefin resin is JIS K7
The heat distortion temperature measured by 207 is 90-200 ° C.,
Preferably 90 to 150 ° C, more preferably 95 to 13
It is good to use what is 0 degreeC. If the temperature is higher than 200 ° C., the flexural modulus at room temperature is too high, and deformation at the time of mounting the insulating gasket occurs, which may cause a crack or a crack.
At a temperature lower than 0 ° C., the resistance of the insulating gasket at a high temperature is inferior, and the sealing performance is reduced. The sealant layer of the organic electrolyte battery of the present invention may be formed, for example, by the following procedure. That is, the sealant composition of the present invention is applied to the surface of a metal container and / or
Alternatively, a predetermined amount of liquid is fed to the surface of the insulating gasket by a fixed amount pump such as an air-driven fixed amount dispenser, a roller pump, and a gear pump, and applied. After the application, the applied material is naturally dried while keeping the sealing agent composition horizontal so that the organic solvent is removed to form a thin layer of diene rubber. However, the application is not limited to a method using a metering pump, and a small amount can be manually applied using a brush. Also, it is needless to say that the drying can be performed in a shorter time by forcibly drying by the heating device, and the process can be a more industrially suitable process. The thickness of the sealant layer provided by such a method may be arbitrarily selected depending on the size of the metal container and the insulating gasket, and is usually 0.1 μm to 1000 μm. If the thickness of the layer is insufficient, problems such as leakage of electrolyte solution and intrusion of moisture may occur, or the layer may be cut off. Conversely, if the layer is too thick, layer formation may be difficult.

[0009]

According to the present invention, a sealant for an organic electrolyte battery having particularly excellent sealing properties at high temperatures can be obtained, and a battery using the sealant is useful as a battery that can be used in a wide range of environments.

[0010]

The present invention will be described more specifically below with reference to examples. Parts and% in each example are based on weight unless otherwise specified. In addition, the weight average molecular weight (hereinafter, referred to as
Mw) is a value measured by gel permeation chromatography using tetrahydrofuran as a solvent. Example 1 5000 g of toluene and 810 g of butadiene were added to a 10-liter autoclave equipped with a stirrer, and the mixture was sufficiently stirred.
7 mol and 0.6 mmol of chromium chloride / pyridine complex were added, and polymerization was carried out at 60 ° C. with stirring for 3 hours. afterwards,
The polymerization was terminated by adding 100 ml of methanol. After termination of the polymerization, the mixture was cooled to room temperature, and then the polymerization liquid was taken out. After the obtained polymerization liquid was subjected to steam coagulation, it was vacuum-dried at 60 ° C. for 48 hours to obtain 780 g of a solid polymer. The Mw of the obtained polymer was 390,000. In addition, ¹³ C-
From the result of NMR spectrum, the cis-form content of this polymer was 94%. This polymer was dissolved in ethylcyclohexane to prepare a sealing composition having a concentration of 10% by weight. Thereafter, using a fixed amount dispenser, a coating material was applied to the surface of the insulating gasket made of polypropylene using a constant-rate dispenser so that the thickness of the sealing material layer after drying became 15 μm, followed by drying to form a sealing material layer.

Separately, a negative electrode was prepared by kneading MCF, which is a fibrous graphite, with a binder using water as a solvent, applying a paste to a copper foil, followed by drying and pressing. The positive electrode was prepared by kneading a paste of LiCoO ₂ together with a binder, applying it to an aluminum foil, drying and pressing. These were wound together with a polyethylene porous separator to form an electrode group. Next, the electrode group was set to an inner diameter of 16
It was inserted into a nickel-plated iron can having a height of 50 mm and a height of 50 mm (17500 type), and a bead was formed in the vicinity of the opening for fixing the sealing portion. The sealant was applied to a portion of the bead portion that was in contact with the insulating gasket using a quantitative dispenser so that the thickness of the sealant layer after drying was 15 microns, followed by drying to form a sealant layer. Then, the mixture was put into a vacuum dryer to completely dry the water adsorbed on the electrode group, and a 1 M solution of LiPF ₆ dissolved in a mixed solvent of ethylene carbonate and methyl ethyl carbonate was injected as an electrolytic solution, and then sealed. Battery. FIG. 1 shows a battery configuration diagram. After these batteries were allowed to stand for 2 days after the electrolyte injection and sealing, the battery was kept at 1 V until the battery voltage reached 4.2 V.
After reaching 4.2 V at a constant current of C, the battery was charged at a constant voltage of 4.2 V for a total of 5 hours to perform an initial charge. Five batteries charged at 4.2 V were heated in a thermostat at 95 ° C. for 48 hours, and the weight change before and after heating was determined. In addition, five batteries also charged to 4.2 V
The sample was dropped 10 times from a height of m in an arbitrary direction, and the change in weight before and after the drop was determined. As a result, no significant weight change was observed in any of the incubation test and the drop test, and it was confirmed that the battery contents were sufficiently sealed.

Example 2 5000 g of toluene and 71 of butadiene were placed in a 10-liter autoclave equipped with a stirrer.
0 g and styrene 100 g, and after sufficiently stirring, N,
A solution of N, N ', N'-tetramethylethylenediamine in toluene (concentration: 0.05 mol / L) is 10 m
l, add Ziegler catalyst (0.2 mmol),
For 4 hours with stirring. Then, methanol 1
The polymerization was stopped by adding 00 ml. After stopping the polymerization, the mixture is cooled to room temperature, and then the polymerization liquid is taken out. After the obtained polymerization liquid was subjected to steam coagulation, it was vacuum-dried at 60 ° C. for 48 hours to obtain 750 g of a solid polymer. The Mw of the obtained polymer was 280,000. From the results of the ¹³ C-NMR spectrum, the cis-form content of this polymer was 93%. Next, this polymer was dissolved in toluene to prepare a sealant composition having a concentration of 15% by weight. A sealant layer was formed on the surface of a cylindrical insulating gasket in the same manner as in Example 1. The thickness of this layer was 17 μm. The same test as in Example 1 was performed using the insulating gasket to which the sealing agent layer was applied. As a result, no significant change in weight was detected in any of the ten batteries, and the contents were sufficiently sealed. It was confirmed that.

Example 3 In a 10-liter autoclave equipped with a stirrer, 5000 g of toluene and 71 of butadiene were added.
After adding 0 g and stirring sufficiently, a toluene solution of n-butyllithium (concentration: 0.01 mol / L) was added to 2 g.
0 ml was added to terminate the polymerization. After termination of the polymerization, the mixture was allowed to cool to room temperature, and then the polymerization liquid was taken out. After the obtained polymerization liquid was subjected to steam coagulation, it was vacuum-dried at 60 ° C. for 48 hours to obtain 650 g of a solid polymer. Mw of the obtained polymer is 2
30,000. From the result of the ¹³ C-NMR spectrum, the cis content of this polymer was 35%. Next, this polymer was dissolved in methylcyclohexane to prepare a sealant composition having a concentration of 10% by weight.
A sealant layer was formed on the surface of a cylindrical insulating gasket in the same manner as in Example 1. The thickness of this layer was 10 μm. As a result of performing the same test as in Example 1 using the insulating gasket to which the sealing agent layer was applied, no significant change in weight was observed in any of the constant temperature storage test and the drop test, and the battery content was sufficient. It was confirmed that the thing was sealed.

In the embodiment of the present invention, MCF, which is a fibrous graphite, is used as a negative electrode active material, LiCoO ₂ is used as a positive electrode active material, and a mixed solvent of ethylene carbonate and methyl ethyl carbonate is used as an electrolyte.
A solution prepared by dissolving 1 M of PF ₆ was used, but the following materials can also be used. The negative electrode active material may be any substance capable of occluding and releasing lithium, such as pyrolytic carbons, cokes (pitch coke, needle coke, petroleum coke, etc.), graphites (natural graphite, artificial graphite, fibrous graphite). , Spherical graphite, etc.), glassy carbons, organic polymer compounds (baked phenolic resin, furan resin, etc. at an appropriate temperature), or metallic lithium, lithium alloy,
Metal-containing compounds, metal oxides, or polymers such as polyacetylene and polypyrrole can also be used. Li _x MO ₂ (where M represents at least one transition metal, preferably at least one of Co and Ni, and 0.05 <x <1.10.) Or a positive electrode active material;
An active material containing Li _x M ₂ O ₄ (where M represents one or more transition metals, preferably Mn and 0.05 <x <1.10.) Is used. Such active materials include, in addition to LiCoO ₂ , LiNiO ₂ , LiNi _y C
o _{(1-y )} O ₂ (provided that 0.05 <x <1.10, 0 <
y <1), and a composite oxide represented by LiMn ₂ O ₄ . For example, the composite oxide is prepared by mixing carbonates of lithium, cobalt, and nickel as starting materials in accordance with the composition, and mixing them in an oxygen-containing atmosphere at 600 to 1%.
It is obtained by firing at 000 ° C. The starting materials are not limited to carbonates, but can be synthesized from hydroxides and oxides. Examples of the electrolyte include propylene carbonate, ethylene carbonate, methyl ethyl carbonate, dimethyl carbonate, diethyl carbonate, γ
LiClO ₄ , LiAs based on a single solvent such as butyl lactone, tetrahydrofuran,
An appropriate mixture of F ₆ , LiPF ₆ , LiBF _{4 and the} like can be used.

Comparative Example 1 In a 10-liter autoclave equipped with a stirrer, 5000 g of cyclohexane and 800 g of butadiene were added. After sufficiently stirring, 100 ml of a toluene solution of n-butyllithium (concentration: 1.65 mol / l) was added. After polymerization at 60 ° C. for 1 hour, the polymerization was stopped with methanol. After termination of the polymerization, the mixture was allowed to cool to room temperature, and then the polymerization liquid was taken out. The obtained polymerization solution is subjected to BHT
Coagulation with a / methanol / acetone solution. After coagulation, 60
Vacuum drying at 48 ° C. for 48 hours gave 800 g of a viscous polymer. Mw of the obtained polymer was 9,000.
From the result of the ¹³ C-NMR spectrum, the cis content of this polymer was 35%. This polymer was dissolved in toluene to prepare a sealant composition having a concentration of 10% by weight. A sealant layer was formed on the surface of a cylindrical insulating gasket in the same manner as in Example 1. The thickness of this layer is 10
μm. Using the insulating gasket to which the sealant layer was applied, the same test as in Example 1 was performed. As a result, the maximum value and the minimum value of the weight loss of the five batteries were 2.04% and 1.01%, respectively, confirming that the battery contents were not sufficiently sealed.

Comparative Example 2 A composition obtained by mixing 100 parts of blown asphalt with a penetration depth of 20 to 40 and 400 parts of toluene was used as a sealant composition. Then, the same test as in Example 1 was performed. As a result, two of the batteries that underwent the high-temperature storage solution
It was confirmed that odor derived from the electrolytic solution was generated from one of the batteries subjected to the drop test and the one subjected to the drop test.
A weight loss of 0-40 mg was observed. After storing these batteries at room temperature for 10 days, the amount of water in the electrolyte was measured by the Karl Fischer method.
Was observed, and it was confirmed that the hermeticity of the battery was reduced.

From the results of the above Examples and Comparative Examples, the sealant of the present invention is superior to a sealant containing diene rubber having a weight average molecular weight of less than 10,000 as a main component or a conventional sealant. It was found to exhibit a tight seal.

[Brief description of the drawings]

FIG. 1 shows a battery configuration diagram in which a part of an organic electrolyte battery is developed.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Negative electrode 2 Separator 3 Positive electrode 4 Can 5 Sealing body 6 Safety valve

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Hiroyuki Hasebe 1 Toshiba, Komukai Toshiba-cho, Saiwai-ku, Kawasaki-shi, Kanagawa Inside R & D Center of Toshiba Corporation

Claims (7)

[Claims] (1) a weight average molecular weight of 10,000 to 1.5;
000, a diene rubber-based sealant for organic electrolyte batteries. 2. A diene monomer homopolymer, a copolymer of two or more diene monomers, or a copolymer of a diene monomer and a non-polar polymerizable monomer, having a weight average molecular weight of 20, 2,000 to 800,000 diene rubber-based sealing agents for organic electrolyte batteries. 3. The sealant for an organic electrolyte battery according to claim 1, wherein the cis content of the diene rubber is 30% or more. 4. The sealant according to claim 1, wherein the diene rubber is a polymer or copolymer of butadiene. 5. The sealant according to claim 1, wherein the sealant has 5 carbon atoms.
A sealant composition obtained by dissolving the composition in an organic solvent of (1) to (15). 6. A space between an insulating gasket mounted on an opening of a metal container containing a power generating element and the metal container, and / or
Or an organic electrolyte battery provided with the sealant layer according to claim 1 between an insulating gasket and a sealing body. 7. The battery according to claim 6, wherein the organic electrolyte battery is a lithium secondary battery or a lithium ion secondary battery.