JP2007324531A - Electrochemical element and electronic device having it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrochemical element which has a high capacity maintenance rate even if put in an atmosphere of a high temperature and high humidity after reflow-soldering. <P>SOLUTION: The electrochemical element is equipped with a separator, a pair of polarizable electrodes opposedly located through the separator, an electrolyte which is impregnated into the pair of polarizable electrodes and the separator, an outer cover and an outer case which hold the separator, the pair of polarizable electrodes, and the electrolyte, and a gasket which is located between the side wall of the outer cover and the side wall of the outer case. The holding space composed of the outer case and the outer cover is sealed by curving the tip of an opening of the outer case inward. The electrolyte is an electrolyte of an organic solvent, and the gasket is mainly made of butyl rubber, and the butyl rubber contains a polymer, a reinforcing material, a filling material, and a secondary material. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an electrochemical element obtained by impregnating a pair of polarizable electrodes facing each other via a separator with an electrolytic solution, and an electronic apparatus including the electrochemical element.

  There is an electric double layer capacitor as one of the electrochemical elements. A structure as shown in FIG. 1 is generally known for an electric double layer capacitor having a coin-type structure. That is, a first polarizable electrode (1) made of activated carbon or the like and a second polarizable electrode (2) made of activated carbon or the like are arranged facing each other with a separator (3) interposed therebetween, and the first polarizable electrode ( The first current collector (6) is provided in 1), the second current collector (7) is provided in the second polarizable electrode (2), and the pair of polarizable electrodes (1), (2) and the separator ( 3) is impregnated with an electrolytic solution, and is stored in a storage space (9) including an outer case (5) and an outer lid (4), and the side wall (5a) of the outer case (5) By disposing an electrically insulating gasket (8) between the outer lid (4) and the side wall (4a), and curving the opening tip (5b) of the outer case (5) inward. The storage space (9) is sealed. (For example, refer to Patent Document 1).

  The electric double layer capacitor is used by being attached to an electronic circuit board as a backup power source for an RTC or a memory of a portable communication device. In recent years, electronic circuit boards used in electronic devices such as portable communication devices are desired to have high performance, multiple functions, and small size, and it is necessary to mount many electronic components. Therefore, cream solder is applied to a portion where an electronic component such as an electric double layer capacitor on the electronic circuit board is attached, and the electronic component is placed on the cream solder application surface and guided to a reflow furnace. A reflow soldering technique is used in which a solder is melted by heating at a high temperature of about 0 ° C. for a short time, and the electronic component is connected to a substrate.

  In order to cope with such high temperatures in the reflow soldering process, polyether ether ketone (hereinafter referred to as PEEK) having excellent heat resistance is used as a gasket material for electric double layer capacitors. In addition, when an aqueous electrolyte is used as the electrolyte, the storage space is heated to a high temperature and high pressure due to heating by the reflow furnace, and the aqueous electrolyte is denatured and the electrochemical characteristics of the electric double layer capacitor are deteriorated. In addition, when an aqueous electrolyte is used, it is difficult to use at high voltage. Therefore, an organic solvent electrolyte is used instead of an aqueous electrolyte in the electric double layer capacitor for reflow soldering.

  The electric double layer capacitor having a gasket made of PEEK is attached to the electronic circuit board for portable communication equipment by heat treatment in a reflow furnace. After the portable communication device incorporating the electronic circuit board is completed, if the inside of the portable communication device is in a high-temperature and high-humidity environment depending on the usage status of the user who purchased the portable communication device, the capacity of the electric double layer capacitor is increased. There is a problem that the initial capacity is significantly decreased (capacity maintenance ratio is decreased).

  In addition, since PEEK is an expensive material, there is a problem that the cost of the electric double layer capacitor increases when a gasket made of PEEK is used.

As a result of intensive studies, the inventors of the present application have found that the above problem can be improved by providing a gasket mainly composed of butyl rubber in an electric double layer capacitor, and the technical content thereof is disclosed in Japanese Patent Application No. 2006-023760. Disclosed.
International Publication No. 05/086190 Pamphlet

  As a result of continuing research, the present inventor has found that the properties of butyl rubber vary greatly depending on the additive and content to be blended, and the degree of improvement in capacity retention rate is low.

  Accordingly, an object of the present invention is to provide an electrochemical element having a high capacity retention rate even when placed in a high-temperature and high-humidity environment after reflow soldering by optimizing the gasket material and content.

  According to a first aspect of the present invention, there is provided a separator (3), a pair of polarizable electrodes (1) and (2) arranged opposite to each other with the separator (3) interposed therebetween, and the pair of polarizable electrodes (1) and (2) and An electrolyte impregnated in the separator (3), an outer lid (4) and an outer case (5) for housing the separator (3), a pair of polarizable electrodes (1) and (2), and the electrolyte; A gasket (8) disposed between a side wall portion (4a) of the outer cover (4) and a side wall portion (5a) of the outer case (5); In the electrochemical element in which the storage space (9) composed of the outer case (5) and the outer lid (4) is sealed by curving 5b) inward, the electrolyte is an organic solvent electrolyte. The gasket (8) is an electrochemical element characterized in that it is made of butyl rubber containing a polymer, a reinforcing material, a filler, and auxiliary materials.

  The butyl rubber is a mixture of 20 to 45 parts by weight of polymer with respect to 68 parts by weight of the polymer exclusion part, and the polymer is preferably composed of isobutylene and isoprene.

  The butyl rubber is more preferably mixed with 25 to 40 parts by weight of the polymer with respect to 68 parts by weight of the polymer exclusion part.

  Preferably, the reinforcing material is carbon black, and the butyl rubber is mixed with 13 to 22 parts by weight of carbon black with respect to 83 parts by weight of the reinforcing material exclusion part.

  More preferably, the butyl rubber is mixed with 15 to 20 parts by weight of carbon black with respect to 83 parts by weight of the reinforcing material exclusion part.

  Preferably, the filler is clay, and the butyl rubber is mixed with 29 to 51 parts by weight of clay with respect to 58 parts by weight of the filler exclusion part.

  The butyl rubber is more preferably mixed with 33 to 47 parts by weight of clay with respect to 58 parts by weight of the filler exclusion part.

  The auxiliary material is a mixture of 3 parts by weight of stearic acid and 5 parts by weight of zinc oxide, and the butyl rubber is a mixture of 4 to 8 parts by weight of the mixture of stearic acid and zinc oxide with respect to 94 parts by weight of the auxiliary material excluded part. It is preferable to do this.

  A second invention is an electronic device including one or more electronic circuit boards, and the electrochemical element of the first invention is attached to at least one of the electronic circuit boards by a heat treatment by a heating device. It is an electronic device characterized by being.

  By changing the mixing ratio of polymers, reinforcing materials, fillers, and auxiliary materials among the butyl rubber materials that make up the gasket, the hardness and strength of the gasket can be adjusted, and the capacity retention rate of the electrochemical device can be increased. It was.

  That is, when butyl rubber is used in the mixing ratio of the present invention, the gasket has an appropriate hardness and strength even in a high-temperature and high-humidity environment, so that the gasket is sufficiently compressed along the outer cover and is hardly damaged. Therefore, since the gap between the outer lid and the gasket hardly appears, the storage space has high sealing performance, and leakage of the electrolytic solution can be suppressed, and the outside air does not corrode the electrolytic solution. Therefore, the capacity retention rate of the electrochemical element can be increased.

  On the other hand, when the hardness and strength of the gasket are high in a high temperature and high humidity environment, the gasket is hardly damaged, but the gasket is not compressed sufficiently. Therefore, the gap between the outer lid and the gasket is not sufficiently filled, the sealing performance of the storage space is lowered, and the level of leakage of the electrolytic solution from the gap is increased. Therefore, the effect of improving the capacity retention rate of the electrochemical element is reduced.

  On the other hand, if the hardness and strength of the gasket are low in a high temperature and high humidity environment, the gasket will be compressed, but the gasket will be easily damaged when pressed against the exterior lid during sealing. There is a gap between them. And the sealing performance of storage space falls by the said clearance gap, and the level of the leakage of electrolyte solution becomes large. Therefore, the effect of improving the capacity retention rate of the electrochemical element is reduced.

  As shown in FIG. 1, the electrochemical device of the present invention has a first polarizable electrode (1) and a second polarizable electrode (2) arranged opposite to each other with a separator (3) interposed therebetween, and A first current collector (6) is provided on the first polarizable electrode (1), and a second current collector (7) is provided on the second polarizable electrode (2). Thereafter, the pair of polarizable electrodes (1 ) (2) and the separator (3) are impregnated with an electrolytic solution and stored in a storage space (9) composed of an outer case (5) and an outer cover (4), and the side wall of the outer case (5) A gasket (8) made of butyl rubber is disposed between the portion (5a) and the side wall (4a) of the exterior lid (4), and the opening tip (5b) of the exterior case (5) is curved inward. By doing so, the storage space (9) is hermetically sealed.

  In the electrochemical device of the present invention, the polarizable electrodes (1) and (2) are composed of an active material and a binder. When the conductivity of the active material is low, a conductive agent may be added. As the active material, powdered activated carbon obtained by activating sawdust, coconut shell, pitch, or the like can be used. Also, activated carbon or activated carbon fiber that has been subjected to infusibilization and carbonization activation treatment for fibers such as phenolic, rayon, acrylic, pitch, etc., in a felt shape, fiber shape, paper shape, or sintered shape Can be used. In addition, carbon materials such as carbon nanotubes and metal compounds can be used. As the binder, known ones generally used in electrochemical devices can be used. For example, polytetrafluoroethylene, polyvinylidene fluoride, polyvinylpyrrolidone, polyvinyl chloride, polyethylene, polypropylene, polyfluoroethylenepropylene, Ethylene-propylene-dientapolymer, styrene butadiene rubber, carboxymethyl cellulose, fluororubber, and the like can be used. As the conductive agent, known ones generally used for electric double layer capacitors can be used. For example, natural graphite such as flake graphite and earth graphite, artificial graphite, carbon black, acetylene black, ketjen Black, carbon fiber, or the like can be used.

  As the separator (3), a resin such as glass fiber, polyphenylene sulfide, polyethylene terephthalate, polyamide, or polyimide is used as an insulating film having a large ion permeability and a predetermined mechanical strength. it can. The pore diameter of the separator (3) may be in the range generally used for capacitors, for example, 0.01 to 5 μm. The thickness of the separator (3) should just be generally used, for example, 10-250 micrometers can be used.

As the electrolytic solution, a solution in which a supporting salt is dissolved in an organic solvent is used. As the organic solvent, cyclic esters, chain esters, cyclic ethers, chain ethers and the like are used. Specifically, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, γ-butyrolactone, 2-methyl-γ-butyrolactone, acetyl-γ-butyrolactone, γ-valerolactone, 1,2-dimethoxyethane, 1,2-ethoxyethane, diethyl ether, diethylene glycol diethyl ether, triethylene glycol diethyl ether, ethylene glycol dialkyl ether, Diethylene glycol dialkyl ether, triethylene glycol dialkyl ether, tetraethylene glycol dialkyl ether, dipropyl carbonate, methyl ethyl carbonate, methyl Butyl carbonate, ethyl propyl carbonate, butyl propyl carbonate, propionic acid alkyl ester, malonic acid dialkyl ester, acetic acid alkyl ester, tetrahydrofuran (THF), alkyltetrahydrofuran, dialkyltetrahydrofuran, alkoxytetrahydrofuran, dialkoxytetrahydrofuran, 1,3-dioxolane, Alkyl-1,3-dioxolane, 1,4-dioxolane, 2-methyltetrahydrofuran, dimethyl sulfoxide, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate, methyl propionate, ethyl propionate, phosphorus At least one kind of acid triester, maleic anhydride, sulfolane, 3-methylsulfolane, etc. Rukoto is also possible. In particular, it is preferable to use a mixture of propylene carbonate or sulfolane because of excellent heat resistance. As the supporting salt, it is preferable to use tetraethylammonium tetrafluoroborate or triethylmethylammonium tetrafluoroborate (C ₂ H ₅ ) ₄ PBF ₄ , (C ₃ H ₇ ) ₄ PBF ₄ , SBP-BF ₄ , ( _{C 2 H 5) 4 PPF 6} , the _{(C 2 H 5) 4 PCF} 3 SO 4, (C 2 H 5) 4 NPF 6, LiClO 4, LiPF 6, LiBF 4, LiN (CF 3 SO 2) 2 , etc. It is also possible to use at least one kind.

  As the gasket (8), butyl rubber mixed with various materials such as a polymer, a reinforcing material, a filler, a vulcanized material (crosslinking material), and auxiliary materials is used. As the polymer, a polymer composed mainly of isobutylene and isoprene can be used. In addition, carbon black is used as a reinforcing material, silica, mica, and clay are used as fillers, resins and sulfur are used as vulcanizing materials, phenols and amines are used as auxiliary materials, and auxiliary materials are used as auxiliary materials. For example, a mixture of zinc oxide and stearic acid can be used.

  Examples of the present invention will be described below.

  The electric double layer capacitor according to the present invention was produced by the following procedure.

(Preparation of polarizable electrode)
Activated carbon, acetylene black and polytetrafluoroethylene were mixed at a weight ratio of 90: 5: 5, and the mixture was formed into a disk shape having a diameter of 10 mm and a thickness of 0.5 mm. A first polarizable electrode and a second polarizable electrode were produced by vacuum drying for a period of time.

(Preparation of electrolyte)
An electrolyte solution was prepared by dissolving triethylmethylammonium tetrafluoroborate as a supporting salt in a concentration of 1.0 mol / l in an organic solvent in which propylene carbonate and sulfolane were mixed at a volume ratio of 50:50. .

(Production of gasket)
Polymer, reinforcing material, filler, isobutylene and isoprene mixture, carbon black, clay, auxiliary material, 3 parts by weight of stearic acid and 5 parts by weight of zinc oxide, and anti-aging agent and vulcanizing material. 3 parts by weight were mixed to produce gaskets provided in Examples 1 to 23. The molar ratio of isobutylene in the polymer was 98 mol%. Tables 1 to 4 show the mixing ratio (parts by weight) in each gasket. Also, a PEEK gasket was prepared as a gasket provided in Comparative Example 1.

(Assembly of coin cell)
As shown in FIG. 1, the exterior lid (4) and the exterior case (5) made of stainless steel each have mounting surfaces (41) and (51) for mounting polarizable electrodes. After applying a conductive paint in which graphite powder and water glass are mixed as a current collector to the mounting surfaces (41) and (51), the first polarizable electrode (1) and the second polarizable electrode (2) are mounted. Put. Then, a glass fiber separator (3) containing the electrolytic solution is placed on the upper surface of the second polarizable electrode (2), and the aforementioned gasket (5a) is placed inside the side wall (5a) of the outer case (5). 8) was placed. Next, an exterior lid (4) is arranged in the exterior case (5) so that the first polarizable electrode (1) is placed thereon, and an opening tip (5b) of the exterior case (5). ) Is curved inward to seal the storage space (9) composed of the outer case (5) and the outer lid (4), and the electric double layers of Examples 1 to 23 and Comparative Example 1 A capacitor was produced.
(Method for measuring capacity retention rate)
Fifty electric double layer capacitors of Examples 1 to 23 and Comparative Example 1 were produced, respectively, and placed in a reflow furnace having a maximum temperature of 250 ° C. twice. Subsequently, after leaving at room temperature and normal humidity for 24 hours, the capacity before the test was measured. Next, in order to investigate the high-temperature and high-humidity storage characteristics, as a high-temperature and high-humidity storage test, it was left in a high-temperature and high-humidity environment (70 ° C., 75% RH, held for 1000 hours) and then left at room temperature and normal humidity for 24 hours. Was measured to calculate the capacity retention ratio (capacity after test ÷ capacity before test × 100). The results are shown in the rightmost column of Table 1. The capacity confirmation condition is 0 to 2 V and 0.5 mA.

  The capacity retention rate of Comparative Example 1 including the PEEK gasket was 62%.

Hereinafter, the results of evaluating the relationship between the amount of the polymer, carbon black, clay, and stearic acid / zinc oxide mixture in the butyl rubber used for the gasket and the capacity retention rate will be described.
(Examination of polymer mixing amount)
Table 1 shows the capacity retention ratios of Examples 1 to 7 in which a gasket made of butyl rubber in which the remaining amount excluding the polymer (hereinafter, polymer excluded portion) is fixed to 68 parts by weight and the amount of the polymer mixed is changed is incorporated.

  As can be seen from Table 1, the capacity retention ratio was as good as 79 to 90% in Examples 1, 3 to 6 (20 to 45 parts by weight of polymer). Particularly in Examples 1, 4, and 5 (25 to 40 parts by weight of polymer), the capacity retention rate was 88 to 90%, which was very good. On the other hand, in Examples 2 and 7, it was 70 and 69%, respectively, which was better than 62% of Comparative Example 1, but not satisfactory.

That is, the capacity maintenance ratio can be improved by using butyl rubber in which 20 to 45 parts by weight of polymer is mixed with 68 parts by weight of the polymer exclusion part, and 25 to 40 parts of polymer with respect to 68 parts by weight of the polymer exclusion part. The capacity retention rate could be further improved by using a mixture of parts by weight.
(Examination of carbon black mixing amount)
The capacity maintenance ratios of Examples 1 and 8 to 13 in which gaskets made of butyl rubber in which the remaining amount excluding carbon black (hereinafter referred to as reinforcing material exclusion portion) was fixed to 83 parts by weight and the mixing amount of carbon black was changed were incorporated. It shows in Table 2.

  As can be seen from Table 2, the capacity retention rate was as good as 80 to 90% in Examples 1 and 9 to 12 (carbon black 13 to 22 parts by weight). Particularly in Examples 1, 10 and 11 (15 to 20 parts by weight of carbon black), the capacity retention rate was 87 to 90%, which was very good. On the other hand, in Examples 8 and 13, it was 72 and 73%, respectively, which was better than 62% of Comparative Example 1, but not satisfactory.

That is, by using butyl rubber in which 13 to 22 parts by weight of carbon black is mixed with 83 parts by weight of the reinforcing material exclusion part, the capacity maintenance ratio can be improved. The capacity retention rate could be further improved by using a mixture of 15 to 20 parts by weight.
(Examination of clay mixing amount)
Table 3 shows capacity retention ratios of Examples 1 and 14 to 19 in which a gasket made of butyl rubber in which the remaining amount excluding clay (hereinafter referred to as filler exclusion portion) is fixed to 58 parts by weight and the mixing amount of clay is changed is incorporated. Shown in

  As can be seen from Table 3, the capacity retention ratio was as good as 78 to 90% in Examples 1 and 15 to 18 (clay 29 to 51 parts by weight). Particularly in Examples 1, 16, and 17 (33 to 47 parts by weight of clay), the capacity retention rate was 88 to 90%, and very good results could be obtained. In contrast, in Examples 14 and 19, they were 68 and 65%, respectively, which were better than 62% of Comparative Example 1, but not satisfactory.

That is, the capacity maintenance rate can be improved by using butyl rubber in which 29 to 51 parts by weight of clay is mixed with 58 parts by weight of the filler exclusion part. The capacity retention rate could be further improved by using a compound containing 47 parts by weight or more.
(Examination of mixing amount of stearic acid and zinc oxide mixture)
The remainder (hereinafter referred to as secondary material exclusion part) excluding the mixture of stearic acid and zinc oxide is fixed to 94 parts by weight, and is made of butyl rubber in which the amount of mixture of stearic acid 3 parts by weight and zinc oxide 5 parts by weight is changed. Table 4 shows the capacity retention rates of Examples 1 and 20 to 23 in which gaskets were incorporated.

  As can be seen from Table 4, the capacity retention rate was as good as 83 to 90% in Examples 1, 2, 22 (4 to 8 parts by weight of a mixture of stearic acid and zinc oxide). On the other hand, in Examples 20 and 23, they were 68 and 65%, respectively, which were better than 62% of Comparative Example 1, but not satisfactory.

  That is, the capacity retention ratio could be improved by using butyl rubber in which 4 to 8 parts by weight of a mixture of stearic acid and zinc oxide was mixed with 94 parts by weight of the auxiliary material exclusion part.

  Therefore, the electric double layer capacitor of the present invention is attached to an electronic circuit board by heat treatment using a heating device such as a reflow furnace, and the electronic circuit board is represented by, for example, a portable communication device represented by a mobile phone, a digital still camera, or a digital video camera. If it is provided in an electronic device such as an imaging device, the desired characteristics of the electronic device can be maintained for a longer time.

  The description of the above-described embodiments is to explain the invention, and should not be construed as limiting the invention described in the claims or reducing the scope, and the configuration of each part of the present invention is not limited to the above-described embodiments. Of course, various modifications can be made within the technical scope described in the claims.

  Although an electric double layer capacitor is illustrated as an electrochemical element, the present invention is not limited thereto, and the present invention can be applied to a coin-type battery or the like.

  The heating apparatus is not limited to the reflow furnace, and any apparatus that can heat-treat the electronic circuit board to which the electrochemical element of the present invention is attached may be used.

  The electronic device is not limited to the above-described portable communication device and imaging device, and any electronic device having an electronic circuit board on which an electrochemical element is mounted is included in the electronic device within the technical scope of the present invention.

It is a longitudinal cross-sectional view of this invention and the conventional electric double layer capacitor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 1st polarizable electrode 2 2nd polarizable electrode 3 Separator 4 Exterior cover 4a Side wall part 5 Exterior case 5a Side wall part 5b Opening front-end | tip 6 1st electrical power collector 7 2nd electrical power collector 8 Gasket 9 Storage space

Claims (9)

A separator (3), a pair of polarizable electrodes (1) and (2) arranged opposite to each other via the separator (3), and the pair of polarizable electrodes (1) and (2) and the separator (3) are impregnated. An outer lid (4) and an outer case (5) for storing the electrolyte solution, the separator (3), the pair of polarizable electrodes (1) and (2), and the electrolyte solution; and the outer lid (4) A gasket (8) is provided between the side wall (4a) and the side wall (5a) of the outer case (5), and the opening tip (5b) of the outer case (5) is curved inward. In the electrochemical element in which the storage space (9) composed of the outer case (5) and the outer lid (4) is sealed,
The electrochemical element is an organic solvent electrolyte, and the gasket (8) is made of butyl rubber containing a polymer, a reinforcing material, a filler, and an auxiliary material.   2. The electrochemical device according to claim 1, wherein the butyl rubber is obtained by mixing 20 to 45 parts by weight of a polymer with respect to 68 parts by weight of the polymer exclusion part, and the polymer is composed of isobutylene and isoprene.   The electrochemical device according to claim 2, wherein the butyl rubber is mixed with 25 to 40 parts by weight of a polymer with respect to 68 parts by weight of the polymer exclusion part.   2. The electrochemical device according to claim 1, wherein the reinforcing material is carbon black, and the butyl rubber is obtained by mixing 13 to 22 parts by weight of carbon black with respect to 83 parts by weight of the reinforcing material exclusion part.   5. The electrochemical device according to claim 4, wherein the butyl rubber is mixed with 15 to 20 parts by weight of carbon black with respect to 83 parts by weight of the reinforcing material exclusion part.   The electrochemical device according to claim 1, wherein the filler is clay, and the butyl rubber is mixed with 29 to 51 parts by weight of clay with respect to 58 parts by weight of the filler exclusion part.   The electrochemical device according to claim 6, wherein the butyl rubber is mixed with 33 to 47 parts by weight of clay with respect to 58 parts by weight of the filler exclusion part.   The auxiliary material is a mixture of 3 parts by weight of stearic acid and 5 parts by weight of zinc oxide, and the butyl rubber is a mixture of 4 to 8 parts by weight of the mixture of stearic acid and zinc oxide with respect to 94 parts by weight of the auxiliary material excluded part. The electrochemical element according to claim 1, wherein   An electronic device comprising one or a plurality of electronic circuit boards, wherein at least one of the electronic circuit boards has the electrochemical element according to claim 1 attached thereto by heat treatment by a heating device. Features electronic equipment.

Images