JP2005209819A - Electrochemical device and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrochemical device which has a high steam barrier property and gas barrier property and hardly has short-circuits between current collectors at the time of sealing and has no adverse thermal effect on a power generation element, and also to provide its manufacturing method. <P>SOLUTION: The electrochemical device comprises a pair of plate-like current collectors 20 and 21, the power generation element 10 which is interposed between the current collectors 20 and 21 so that a first electrode 12 may be in contact with the current collector 20 and a second electrode 13 may be in contact with the other current collector 21, and a sealing member 30 which fills up a space between the peripheral portion 20a of the current collector 20 and the peripheral portion 21a of the current collector 21 to encapsulate the power generation element 10. The sealing member 30 is composed of a thermoplastic high molecular inner portion 32 which is thermally fused to the peripheral portions 20a and 21a of the current collectors 20 and 21 and surrounds the power generation element 10, and a liquid-crystal high molecular outer portion 34 which is thermally fused to the peripheral portions 20a and 21a of the current collectors 20 and 21 and surrounds the inner portion 32 from the outside and has a higher melting point than that of the inner portion 32. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to electrochemical devices such as electric double layer capacitors and lithium secondary batteries, and methods for producing these electrochemical devices.

  Conventionally, electrochemical devices such as electric double layer capacitors and lithium secondary batteries have been widely used in mobile phones, PDAs and the like.

  As such an electrochemical device, a power generation element having a pair of electrodes and an electrolyte is sandwiched between a pair of current collectors larger than the power generation element, and a thermoplastic sealing material disposed between the peripheral portions of the current collector is collected. An electrochemical device having a hermetically sealed structure fused with an electric body has been devised.

  As a sealing material for such an electrochemical device, for example, a polyolefin in which an ethylene copolymer sheet having a melting point lower than that of a high-density polyethylene sheet and modified with an unsaturated carboxylic acid or the like is laminated on both surfaces of the high-density polyethylene sheet. The sealing material made from manufacturing is known (refer patent document 1).

  In addition to this, a polyolefin sealing material comprising polyisobutylene-modified polyethylene (see Patent Document 2), modified polypropylene, modified polyethylene (Patent Document 3), acid-modified polyolefin containing fine particle filler (Patent Document 4), and the like. It has been known.

On the other hand, a sealing material made of a liquid crystalline polymer having excellent gas barrier properties is also known (Patent Document 5).
Japanese Patent Laid-Open No. 62-154469 JP-A-2-234344 JP-A-4-121947 JP-A-6-349462 JP 2003-92092 A

  However, electrochemical devices using a sealing material made of polyolefin sometimes have insufficient water vapor barrier properties and gas barrier properties. On the other hand, in an electrochemical device using a sealing material made of a liquid crystalline polymer, since the melting temperature of the sealing material is high, the power generation element may be adversely affected by heat at the time of thermal fusion.

  The present invention has been made in view of the above problems, and has an excellent water vapor barrier property and gas barrier property, and an electrochemical device that hardly causes an adverse effect due to heat on a power generation element when heat sealing a sealing material, and a method for producing the same The purpose is to provide.

  An electrochemical device according to the present invention includes a pair of plate-like current collectors facing each other, a first electrode, a second electrode, and an electrolyte provided between the electrodes, and the first electrode is one of the current collectors. A power generation element sandwiched between the current collectors so that the second electrode is in contact with the other current collector and a gap between the peripheral edge of one current collector and the peripheral edge of the other current collector And a frame-shaped sealing material for sealing and sealing the power generation element between the current collectors. The sealing material surrounds the power generation element and is thermally fused to the peripheral part of one current collector and the peripheral part of the other current collector, and the inner part is outside An outer portion made of a liquid crystalline polymer that is thermally fused to the peripheral portion of one current collector and the peripheral portion of the other current collector. Melting temperature is lower than molecules.

  Here, the “liquid crystalline polymer” is a thermotropic polymer that exhibits liquid crystallinity in a molten state, that is, a property in which the polymer chain is oriented, by strong interaction between polymer chains. Such a liquid crystalline polymer layer exhibits high heat resistance, low linear expansion coefficient, high insulation, low hygroscopicity, and high gas barrier properties as compared with a general thermoplastic polymer.

  According to the present invention, the liquid crystal polymer has an outer portion, and the liquid crystal polymer has higher water vapor transmission rate and oxygen transmission rate than other thermoplastic polymers, so that the gas barrier property of the sealing material is increased. The reliability of electrochemical devices can be improved. Moreover, the inner side part whose melting temperature is lower than an outer side part is provided inside the outer side part. For this reason, the inner part closer to the power generation element than the outer part of the sealing material can be thermally fused to the current collector at a lower temperature than the outer part. Thereby, compared with the case where the sealing material which consists only of a liquid crystalline polymer is used, it is hard to give the bad influence by a heat | fever with respect to an electric power generation element at the time of heat fusion.

  Here, as the liquid crystalline polymer on the outer side, when a polymer having a melting temperature of about 180 to 350 ° C. is used, heat fusion can be easily performed, and the adverse effect of heat on the power generation element can be sufficiently suppressed by the inner side. .

In addition, when the water vapor permeability of the liquid crystalline polymer on the outer side is 1 g / (m ² · 24 hr · 100 µm) or less and the oxygen permeability is 10 mL / (m ² · 24 hr · 100 µm), sufficient gas barrier properties are obtained. And the reliability of the electrochemical device is sufficiently improved.

  Here, the liquid crystalline polymer preferably contains liquid crystalline polyester.

  On the other hand, when the melting temperature of the thermoplastic polymer in the inner part is 90 to 200 ° C., it is excellent in reducing damage to the power generation element due to heat at the time of heat-sealing the inner part, and has sufficient heat resistance. Become.

  In particular, when the melting temperature of the liquid crystalline polymer on the outer side is 180 to 350 ° C. and the melting temperature of the thermoplastic polymer on the inner side is 90 to 200 ° C., power generation by heat at the time of heat sealing the sealing material Reduces damage to elements at a high level.

  Moreover, when the inner part and the outer part are bonded to the current collector with an adhesive strength of 0.65 N / mm (1/15 kg / mm) or more, the sealing performance is sufficiently exhibited, and the mechanical properties of the electrochemical device are increased. Strength increases. Here, the adhesive strength in the claims and the specification is an adhesive strength defined by JIS K6848.

  Here, the thermoplastic polymer preferably contains polyolefin.

  Moreover, the inner side part and the outer side part can be adhere | attached with the adhesive agent. Moreover, the inner side part and the outer side part may be heat-sealed with each other. In this case, the mechanical strength of the electrochemical device can be increased.

  Further, the inner part is a laminated body in which a plurality of sub-layers having different melting temperatures are laminated in a direction approaching the power generation element, and at this time, the melting temperature of each sub-layer in the laminated body becomes lower as the power generation element is approached. May be.

  In this case, the part near the power generation element in the inner part can be heat-sealed with the current collector at a lower temperature than the part far from the power generation element in the inner part. Therefore, it is possible to sufficiently bond the sealing material and the current collector while further sufficiently suppressing the heat damage of the power generation element when the current collector is heat-sealed with the sealing material.

  Moreover, it is preferable that the outer part of the sealing material is further heat-sealed to the end face of the current collector to surround the end face of the current collector.

  In this case, since the sealing material is further bonded using the end face of the current collector, the gas barrier property can be further improved and the mechanical strength of the electric double layer capacitor can be sufficiently increased.

  A method for producing an electrochemical device according to the present invention includes a first electrode, a second electrode, a power generation element having an electrolyte provided between these electrodes, a pair of plate-like current collectors, and a thermoplastic polymer The thermoplastic polymer has an inner part that can surround the power generation element and an outer part that is made of a liquid crystalline polymer and can surround the inner part, and the melting temperature of the thermoplastic polymer is higher than the melting temperature of the liquid crystalline polymer. A lower sealing material, one current collector is in contact with the first electrode of the power generation element, the other current collector is in contact with the second electrode of the power generation element, and the inner part surrounds the power generation element An arrangement process in which the outer part surrounds the inner part, and the power generation element and the sealing material are sandwiched between a pair of plate-like current collectors, and the inner part of the sealing material is heated to the first temperature and the inner part Is heat-sealed with the current collector, and the outer part of the sealing material is heated to a second temperature higher than the first temperature. And a heating step of the current collector and heat-sealing the outer portion is heated to.

  According to the present invention, the above-described electrochemical device can be suitably manufactured.

  Here, in the heating step, the sealing material is heated by bringing the heating means into contact with the current collector, and the temperature of the portion of the heating means that faces the outer side across the current collector is set to the current collector of the heating means. You may make it higher than the temperature of the part which opposes an inner part on both sides of a body. According to this, the inner part and the outer part of the sealing material can be efficiently heat-sealed with the current collector at once.

  In the heating step, the sealing member is heated by bringing the heating means into contact with the current collector, and the heating means is brought into contact with the portion of the current collector facing the sealing material, while the power generating element of the current collector It is preferable not to contact the portion facing the. Thereby, the heat damage of the power generation element can be sufficiently reduced.

  Further, when the portion of the current collector that faces the power generation element is cooled in the heating step, heat is hardly transmitted to the power generation element via the current collector in the heating step, and the adverse effects of heat can be sufficiently reduced.

  ADVANTAGE OF THE INVENTION According to this invention, the electrochemical device which has high gas barrier property, and is hard to give the bad influence by a heat | fever with respect to an electric power generation element at the time of the heat sealing | fusion of a sealing material is provided, and its manufacturing method.

  Hereinafter, preferred embodiments of an electrochemical device according to the present invention will be described in detail with reference to the drawings. In the following description, the same or corresponding parts are denoted by the same reference numerals, and redundant description is omitted.

(First embodiment)
First, with reference to FIG.1 and FIG.2, the electric double layer capacitor 1 as an electrochemical device of 1st embodiment which concerns on this invention is demonstrated.

  The electric double layer capacitor 1 mainly includes a power generation element 10, a pair of plate-like current collectors 20, 21 that are opposed to each other with the power generation element 10 interposed therebetween and function as external electrodes and an exterior body. A frame-shaped sealing member 30 that closes the gap between the peripheral edge portion 20 a and the peripheral edge portion 21 a of the current collector 21 and seals the power generation element 10 between the current collectors 20 and 21 is provided.

  The power generation element 10 includes a first electrode 12 as a positive electrode and a second electrode 13 as a negative electrode facing each other, a separator 14 disposed adjacent to the first electrode 12 and the second electrode 13, And an electrolyte solution (not shown) containing an electrolyte contained in the electrode 12, the second electrode 13, and the separator.

  The first electrode 12 and the second electrode 13 are electron conductive porous bodies. The constituent material of the first electrode 12 and the second electrode 13 is not particularly limited, and is used as a porous layer constituting a polarizable electrode such as a carbon electrode used in a known electric double layer capacitor. Similar materials can be used. For example, it is obtained by activating treatment of raw coal (for example, petroleum coke produced from a delayed coker using a bottom oil of a fluid catalytic cracking apparatus of heavy petroleum oil or a residual oil of a vacuum distillation apparatus as a raw oil). What has a carbon material (for example, activated carbon) as a main component of a constituent material can be used. Other conditions (types and contents of constituent materials other than carbon materials such as binder) are not particularly limited. For example, a conductive auxiliary agent (carbon black or the like) for imparting conductivity to the carbon powder or a binder (polytetrafluoroethylene (PTFE) or the like) may be added.

  The separator 14 disposed between the first electrode 12 and the second electrode 13 is not particularly limited as long as it is formed of an electrically insulating porous body, and a separator used for a known electric double layer capacitor is used. can do. For example, as the electrically insulating porous body, at least one selected from the group consisting of a laminate of films made of polyolefin such as polyethylene and polypropylene, a stretched film of a mixture of the above resins, or cellulose, polyester and polypropylene Examples thereof include a fiber nonwoven fabric made of a constituent material.

Here, in order to suppress a short circuit between the first electrode 12 and the second electrode 13, the separator 14.
Is larger than the area of the main surface of the electrodes 12 and 13, and the end of the separator 14 is preferably protruded from the end surfaces of the electrodes 12 and 13. At this time, the end face of the separator 14 is preferably separated from the sealing material 30.

  The electrolyte solution is contained in the holes of the first electrode 12, the second electrode 13, and the separator 14. The electrolyte solution is not particularly limited, and an electrolyte solution (an electrolyte salt aqueous solution or an electrolyte salt solution using an organic solvent) used in a known electric double layer capacitor can be used. However, the aqueous solution of the electrolyte salt is electrochemically low in decomposition voltage, and the withstand voltage of the electric double layer capacitor 1 is limited to be low. Therefore, the electrolyte solution is preferably an electrolyte solution (nonaqueous electrolyte solution) using an organic solvent. .

  In the present embodiment, the electrolyte solution may be a gel electrolyte obtained by adding a gelling agent in addition to the liquid state. Further, instead of the electrolyte solution, a solid electrolyte (a solid polymer electrolyte or an electrolyte made of an ion conductive inorganic material) may be contained.

  The current collectors 20 and 21 are rectangular plate-like conductive materials having an area larger than the areas of the main surfaces of the first electrode 12 and the second electrode 13 of the power generation element 10. These current collectors 20, 21 have a power generation element 10 from above and below such that the lower current collector 21 is in surface contact with the second electrode 13 and the upper current collector 20 is in surface contact with the first electrode 12. Is sandwiched. The material of the current collectors 20 and 21 is not particularly limited as long as it is a good conductor capable of sufficiently transferring charges, and a current collector used in a known electric double layer capacitor can be used.

  As a material for the current collector in the case of a non-aqueous electrolyte, a conductive material rich in corrosion resistance can be used. For example, a metal foil such as aluminum or titanium can be used. The thickness of the metal foil is, for example, about 10 to 100 μm.

  The sealing material 30 has a frame shape surrounding the power generation element 10 and is disposed so as to close the gap between the peripheral portions 20a and 21a of the current collectors 20 and 21. The sealing material 30 seals the power generation element 10 between the current collectors 20 and 21. The sealing material 30 has an inner part 32 and an outer part 34. The inner portion 32 surrounds the power generation element 10 at a position closer to the power generation element 10 than the outer portion 34 and forms a rectangular frame shape. The outer portion 34 has a rectangular frame shape surrounding the inner portion 32 from the outside.

  Both ends of the inner portion 32 and the outer portion 34 in the thickness direction are on the inner side surface (the surface closer to the current collector 21) 20 c in the peripheral portion 20 a of the current collector 20 and in the peripheral portion 21 a of the current collector 21. The inner side surfaces (surfaces close to the current collector 20) 21c are thermally fused to each other.

  The adhesive strength between the inner part 32 and the outer part 34 and the current collectors 20 and 21 is not particularly limited, but is 0.65 N / mm ((1/15) kg / mm) or more. This is preferable from the standpoint of increasing the mechanical strength of the capacitor 2 and the sealing property.

  The outer peripheral surface of the outer portion 34 of the frame-shaped sealing material 30 forms the same surface as the end surfaces 20b and 21b of the current collectors 20 and 21, as shown in FIGS. Further, the width W32 of the inner portion 32 and the width W34 (see FIGS. 1 and 2) of the outer portion 34 when viewed from the direction perpendicular to the main surface of the current collector 20 are about 0.2 to 20 mm, respectively. The thickness is preferably about 1 to 10 mm.

  The thickness of the sealing material 30 is preferably matched to the thickness of the power generation element 10.

  Here, the inner part 32 is formed from a thermoplastic polymer. The thermoplastic polymer is not particularly limited as long as it is a thermoplastic polymer having a melting temperature lower than that of the outer portion 34 (details will be described later), and fluorine resin such as polyolefin, polyester, polyvinylidene fluoride, and a copolymer thereof, and the like Is mentioned. In particular, polyolefin is preferable as the thermoplastic polymer of the inner portion 32 from the viewpoints of economy, heat sealability, chemical stability, moisture permeability, and the like. Examples of the polyolefin include polyethylene, polypropylene, acid-modified polyethylene, and copolymers containing these. These thermoplastic polymers can be used alone or in combination of two or more. Moreover, in order to further improve the performance of the thermoplastic polymer, known additives can be contained as necessary.

  Further, it is preferable that the melting temperature of the inner portion 32 is 90 to 200 ° C. because the influence of heat on the power generating element 10 can be sufficiently reduced and sufficient heat resistance can be obtained.

  On the other hand, the outer portion 34 is formed of a liquid crystalline polymer. The liquid crystalline polymer is a thermotropic polymer that exhibits liquid crystallinity in a molten state, that is, a property in which the polymer is aligned, due to strong intermolecular interaction. Examples of such a liquid crystalline polymer include fully aromatic and semi-aromatic liquid crystal polyesters.

  The wholly aromatic polyester includes a combination of an aromatic dicarboxylic acid, an aromatic diol and an aromatic hydroxycarboxylic acid, a combination of different types of aromatic hydroxycarboxylic acids, an aromatic dicarboxylic acid and a nucleus-substituted aromatic. The thing which consists of a combination with diol is mentioned. Examples of the semi-aromatic polyester include those obtained by reacting an aromatic hydroxycarboxylic acid with a polyester such as polyethylene terephthalate. Here, for example, instead of the above-described aromatic dicarboxylic acid, aromatic diol, and aromatic hydroxycarboxylic acid, their ester-forming derivatives may be used.

  Such a liquid crystalline polymer has low hygroscopicity, good chemical resistance, high heat resistance, and forms an anisotropic melt at a temperature of approximately 400 ° C. or lower.

  In addition, the heat resistance of the liquid crystalline polymer mainly depends on the ratio of the aromatic ring in the molecular chain. For example, the melting temperature of a liquid crystalline polymer whose main chain is composed of a phenylene group is approximately 260 to 350 ° C., and the melting temperature of a liquid crystalline polymer having a naphthalene skeleton introduced into the main chain is approximately 190 to 270 ° C. The melting temperature of the liquid crystalline polymer having an ethylene group introduced into the main chain is about 60 to 230 ° C. In the present embodiment, it is particularly preferable to use a liquid crystalline polymer having a melting temperature of about 180 ° C. to 350 ° C.

  The outer portion 34 may be made of only a liquid crystalline polymer, but may be made of a liquid crystalline polymer composition containing other polymer materials in addition to the liquid crystalline polymer. As other resin, thermoplastic resins, such as an epoxy-unit-containing ethylene copolymer, are mentioned, for example. The mixing ratio is, for example, 44 to 1% by weight of another polymer material with respect to 56 to 99% by weight of the liquid crystalline polymer. Moreover, in order to further improve the performance, this liquid crystalline polymer can contain a known additive as required.

  Here, the gas barrier property of such a liquid crystalline polymer will be described.

  For example, FIG. 3 shows an example of a water vapor transmission rate and an oxygen transmission rate of a layer of a liquid crystal polyester polymer composition as an example of a liquid crystalline polymer (Japanese Patent Laid-Open No. 1997-77960), and FIG. An example of water vapor permeability and oxygen permeability of other thermoplastic polymer layers (Toshiyuki Mibu, Kazuyuki Horie, Hansaku Shiraishi, Polymer Materials (Material Technology 16), The University of Tokyo Press, published in November 1984) Show.

これにより、液晶性高分子は、他の熱可塑性高分子に比して群を抜いて水蒸気透過率や酸素透過率が低い、すなわち、ガスバリア性が高いことが理解される。 Here, the liquid crystal polyester composition G-1 is (a) 77% by weight of a particulate wholly aromatic polyester having a structural unit represented by the following formula (1) and having a melting temperature of 324 ° C., and (B) A liquid crystalline polymer composition containing 23% by weight of Bond First 7M manufactured by Sumitomo Chemical Co., Ltd. In addition, the liquid crystal polyester composition G-4 is (a) 87% by weight of particulate wholly aromatic polyester having a structural unit represented by the following formula (2) and having a melting temperature of 270 ° C., and (b) Sumitomo Chemical. It is a liquid crystalline polymer composition containing 13% by weight of Bond First 20B manufactured by Kogyo Co., Ltd.

Thereby, it is understood that the liquid crystalline polymer is superior to other thermoplastic polymers and has a low water vapor transmission rate and oxygen transmission rate, that is, a high gas barrier property.

In the present embodiment, the liquid crystal polymer of the outer portion 34 has a water vapor transmission rate of 1 g / (m ² · 24 hr · 100 μm) or less and an oxygen transmission rate of 10 mL / (m ² · 24 hr · 100 μm). When is used, sufficient gas barrier properties are obtained, and the reliability of the electrochemical device is sufficiently improved.

  Here, the inner portion 32 and the outer portion 34 may be in contact with each other, but may be separated from each other with a predetermined gap. If they are in contact with each other, the strength of the electric double layer capacitor 2 can be improved if they are heat-sealed to each other. In addition, when the inner side part 32 and the outer side part 34 are contacting, when this inner side part 32 and the outer side part 34 are heat-seal | fused to the electrical power collectors 20 and 21, more or less will be heat-seal | fused. .

(Method for manufacturing electric double layer capacitor)
Next, an example of a method for manufacturing the electric double layer capacitor 1 described above will be described with reference to FIGS.

  First, a pair of current collectors 20 and 21 shown in FIG. These current collectors 20 and 21 can be formed, for example, by cutting a conductive metal foil such as aluminum into a rectangular shape having a predetermined size.

  Next, the sheet-like first electrode 12 and the second electrode 13 are respectively formed at the central portion of the main surface of each of the current collectors 20 and 21. The formation method of these 1st electrode 12 and the 2nd electrode 13 is not specifically limited, The well-known thin film manufacturing technique employ | adopted for manufacture of the well-known electric double layer capacitor 1 can be used.

  For example, when the first electrode 12 and the second electrode 13 are carbon electrodes (polarizable electrodes), a sheet-like electrode can be produced using a carbon material such as activated carbon that has been activated by a known method. Specifically, for example, after pulverizing the carbon material to about 5 to 100 μm and adjusting the particle size, for example, a conductive auxiliary agent (carbon black or the like) for imparting conductivity to the carbon powder, for example, a binder, For example, an organic solvent such as MIBK may be added and kneaded to obtain a paste, and this paste may be applied to each of the current collectors 20 and 21 and dried. Application can be performed by metal mask printing, a doctor blade method, a roll press method, or the like.

  Here, as the conductive auxiliary agent, acetylene black, powdered graphite, etc. can be used in addition to carbon black, and as the binder, in addition to polytetrafluoroethylene, polyvinylidene fluoride, fluororubber Etc. can be used.

  Instead of forming the first electrode 12 and the second electrode 13 by applying a paste on the current collectors 20 and 21, sheet-like electrodes are formed and laminated on the current collectors 20 and 21. May be.

  Next, the separator 14 is prepared. The separator 14 can be formed by cutting a porous insulating material such as paper into a predetermined size. Here, the area of the main surface of the separator 14 is preferably larger than those of the first electrode 12 and the second electrode 13.

  Subsequently, a frame-shaped sealing material 30 is prepared. Here, first, a thermoplastic polymer sheet and a liquid crystal polymer sheet having the same thickness are prepared. Then, the thermoplastic polymer sheet is cut into a predetermined frame shape to form the inner portion 32, and the liquid crystalline polymer sheet is cut to a frame shape larger than the inner portion 32 to form the outer portion 34, thereby obtaining the sealing material 30.

  Subsequently, as shown in FIG. 5B, the frame-shaped sealing material 30 obtained in this way is placed on the peripheral portion 21 a of the current collector 21. At this time, the sealing material 30 is arranged so that the inner part 32 of the sealing material 30 surrounds the second electrode 13 and the outer part 34 surrounds the inner part 32. Then, the sealing material 30 is heated to fix the sealing material 30 to the current collector 21. Specifically, the sealing material 30 and the current collector 21 are sandwiched between a surface plate 91 and a surface plate 92 with a heater and heat-sealed. Here, the surface plate 92 with a heater has an annular low temperature heater 92a facing the inner portion 32 with the current collector 21 in between, and an annular high temperature heater 92b facing the outer portion 34 with the current collector 21 in between. doing. The liquid crystalline polymer in the outer portion 34 is heated and melted by the high temperature heater 92b, while the thermoplastic polymer in the inner portion 32 is heated and melted by the low temperature heater 92a so that the inner portion 32 and the outer portion 34 are collected by the current collector. 21 is heat-sealed.

  Subsequently, the above-described electrolyte solution is dropped on the second electrode 13 formed on the current collector 21, and the electrolyte solution is also dropped on the first electrode 12 formed on the other current collector 20.

  Subsequently, as shown in FIG. 6, the separator 14 is laminated on the second electrode 13, and the electrolyte solution is dropped on the separator 14.

  Next, the other current collector 20 is laminated on the current collector 21 to form a laminated structure. At this time, the current collector 20 is stacked on the current collector 21 so that the first electrode 12 is in contact with the separator 14 and the peripheral portion 20 a of the current collector 20 is in contact with the frame-shaped sealing material 30.

  Thereafter, the laminated structure placed on the surface plate 93 is sandwiched between the heat presses 100 from above and heat-sealed while evacuating in a vacuum vessel. Here, the heat press 100 includes an annular low-temperature heater (heating means) 102 facing the inner portion 32 of the sealing material 30 with the current collector 20 in between, and an outer portion 34 of the sealing material with the current collector 20 in between. An annular high-temperature heater (heating means) 104 facing the current collector 20, a cooling unit 108 facing the power generation element 10 across the current collector 20, and the low-temperature heater 102, the high-temperature heater 104 and the cooling unit 108 below, that is, collecting current And a press head 106 for pressing toward the body 20.

  The low-temperature heater 102 contacts the current collector 20 and presses the current collector 20, and the inner portion 32 is heated and melted through the current collector 20 to melt the peripheral portion 20 a and the inner portion of the current collector 20. And 32 are heat-sealed. Here, the inner portion 32 is heated to, for example, about 130 to 160 ° C. by the low-temperature heater 102.

  The high temperature heater 104 is in contact with the current collector 20 to press the current collector 20, and heats and melts the outer side portion 34 through the current collector 20, so that the peripheral portion 20 a and the outer side portion of the current collector 20 are heated. 34 is heat-sealed. The temperature of the high temperature heater 104 is set higher than that of the low temperature heater 102. Here, the outer portion 34 is heated to, for example, about 250 to 300 ° C. by the high temperature heater 104. That is, when the sealing material 30 is heat-sealed to the current collector 20, the temperature of the heating means is changed between the side close to the power generation element 10 and the side far from the power generation element 10.

  As such a low temperature heater 102 or high temperature heater 104, for example, a known heater made of a high melting point metal such as tungsten or tantalum or a high resistance ceramic material such as SiC can be appropriately used. For example, a linear heater may be arranged in a ring shape, or a plate or ribbon heater may be processed in a ring shape. In order to make the temperature of the heaters 102 and 104 uniform inside each heater, the shape of the inner part 32 and the outer part 34 of the sealing material 30 is relatively simple, an annular shape, a square frame shape, and a rectangular frame shape. Preferably there is.

  The cooling unit 108 has a cavity 108a inside and is made of a material having good heat conductivity such as metal. Cooling water is supplied to the cavity 108a through the line 109a, and the cooling water in the cavity 108a is discharged to the outside through the line 109b. As a result, the cooling unit 108 can cool the central portion of the current collector 20 that is in contact with the cooling unit 108, so that the power generation element 10 is not adversely affected by the heat at the time of heat fusion. Here, for example, the central portion of the current collector 20 can be cooled so that the power generation element 10 is maintained at 60 ° C. or less by the cooling unit 108. In addition, when the melting temperature of the inner part 32 and the outer part 34 is low, or when the heat resistance of the power generation element 10 is high, the cooling unit 108 may not be water-cooled, and further, a heat press without the cooling unit 108. Even in the case, heat fusion with reduced influence of heat on the power generation element 10 is possible. In this case, it is preferable that the heater does not contact the central portion of the current collector 20.

  The press head 106 is a member made of metal or the like for pressing the low temperature heater 102, the high temperature heater 104, and the cooling unit 108 toward the surface plate 93. The press pressure may be a pressure that can bring the sealing material 30 in a molten state into close contact with the current collector 20.

  The electric double layer capacitor 1 shown in FIG. 1 is obtained through the process of heat-sealing the sealing material 30 and the current collector 20 with such a heat press 100.

  Instead of the heat press 100 as shown in FIG. 6, for example, a heat press 150 as shown in FIG. 7 may be used.

  Such a heat press 150 includes heat conducting members 112 and 114 having good heat conductivity between the low temperature heater 102 and the current collector 20 and between the high temperature heater 104 and the current collector 20, respectively. ing. In this case, the heat conducting members 112 and 114 may be formed in an annular shape corresponding to the surface shapes of the inner portion 32 and the outer portion 34, respectively. The shapes of the heater 102 and the high temperature heater 104 are relatively free. The material of the heat conducting members 112 and 114 may be any material that can withstand the pressure during pressing and has good thermal conductivity, and a metal material such as stainless steel or tungsten can be suitably used. Here, the heat conducting member 112 and the heat conducting member 114 constitute a heating means. Further, the temperature of the heat conducting member 112 is set lower than the temperature of the heat conducting member 114, and such temperature control is performed by the low temperature heater 102 and the high temperature heater 104.

  Further, instead of the heat press 100 as shown in FIG. 6, a heat press having the low temperature heater 102 without the high temperature heater 104 and a heat press having the high temperature heater 104 without the low temperature heater 102. Can be heat-sealed with the sealing material 30 in which the influence of heat on the power generation element 10 is reduced.

  Thus, the manufacturing process of the electric double layer capacitor 1 according to this embodiment is completed.

  According to this, in the sealing material 30, the inner side 32 made of a thermoplastic polymer is formed on the inner side, and the outer side made of a liquid crystalline polymer having a higher melting temperature than the inner side 32 made of a thermoplastic polymer. An outer portion 34 is present. Here, the liquid crystalline polymer of the outer portion 34 has higher water vapor transmission rate and oxygen transmission rate than the thermoplastic polymer of the inner portion 32. Therefore, since the gas barrier property is high and the deterioration of the power generation element 10 due to the ingress of water vapor or oxygen, the evaporation of the electrolyte solution when exposed to high temperature, and the like are suppressed, the highly reliable electric double layer capacitor 1 is provided. The

  Further, since the inner part 32 has a melting temperature lower than that of the outer part 34, the inner part 32 close to the power generation element 10 in the sealing material 30 can be thermally fused to the current collector 20 at a lower temperature than the outer part. Therefore, it is difficult for the power generation element 10 to be adversely affected by heat when the sealing material 30 is heat-sealed.

  As a result, it is possible to improve the reliability and extend the life of the electric double layer capacitor 1. In addition, you may seal by ultrasonic welding etc., without using a heater, and the same effect is produced.

(Second embodiment)
Next, the electric double layer capacitor 2 according to the second embodiment will be described with reference to FIG. The electric double layer capacitor 2 according to the present embodiment is different from the electric double layer capacitor 1 according to the first embodiment in that a sealing material 40 is provided instead of the sealing material 30, and the sealing material 40 is a sealing material. The difference from the material 30 is that the inner portion 32 and the outer portion 34 are bonded by an adhesive 36.

  By using the adhesive 36, the inner part 32 and the outer part 34 can be bonded sufficiently firmly. In this case, the strength of the sealing material 30 is increased, and the strength of the electric double layer capacitor 2 is increased.

  The material of the adhesive 36 is not particularly limited as long as the inner part 32 and the outer part 34 can be sufficiently bonded. For example, urethane, epoxy, ester, ether, acrylic, and olefin adhesives are used. Or a cured product of a curable resin such as a composite adhesive such as urethanized polyether or urethanized polyester, that is, a product that cures by a chemical reaction after application and bonds the inner portion 32 and the outer portion 34 to each other. Can be used.

  Here, the thickness of the adhesive 36 is preferably as thin as possible, and is preferably 0.5 to 3 μm, for example.

(Third embodiment)
Subsequently, the electric double layer capacitor 3 according to the third embodiment will be described with reference to FIG. The electric double layer capacitor 3 according to this embodiment is different from the electric double layer capacitor 1 according to the first embodiment in that a sealing material 50 is provided instead of the sealing material 30. The sealing material 50 is different from the sealing material 30 in that the inner portion 32 is a laminate. The inner portion 32 is formed by laminating a plurality of thermoplastic polymer sub-layers 32 a and 32 b having different melting temperatures toward the power generation element 10.

  The material of each of the sublayers 32a and 32b is not particularly limited as long as the melting temperature is lower than that of the material of the outer portion 34. For example, when a polyolefin that has not been acid-modified is used for the sub-layer 32 b and an acid-modified polyolefin is used for the sub-layer 32 a, a laminate in which the melting temperature decreases toward the power generation element 10 can be suitably formed.

  Such a sealing material 50 includes, for example, a high-temperature heater for heating the outer portion 34, a medium-temperature heater for heating the sub-layer 32a, and a low-temperature heater for heating the sub-layer 32b in order from the outside. Can be sealed with.

  Such an electric double layer capacitor 3 also exhibits the same effects as the first embodiment. In addition, since the sublayer 32b closest to the power generation element 10 in the inner portion 32 of the sealing material 50 can be heat-sealed with the current collectors 20 and 21 at a lower temperature than the sublayer 32a of the inner portion 32, the current collector Adhesiveness between the sealing material 50 and the current collectors 20 and 21 can be sufficiently enhanced while sufficiently suppressing thermal damage of the power generation element 10 when the body 20 is heat-sealed with the sealing material 30.

(Fourth embodiment)
Next, the electric double layer capacitor 4 according to the third embodiment will be described with reference to FIG. The electric double layer capacitor 4 according to the present embodiment is different from the electric double layer capacitor 1 according to the first embodiment in that a sealing material 60 is provided instead of the sealing material 30, and the sealing material 60 is the sealing material. The difference from 30 is that the outer portion 34 is further heat-sealed to the end faces of the current collectors 20 and 21 to surround the end faces of the current collectors 20 and 21.

  Such an electric double layer capacitor 4 is provided with an outer portion 34 that comes into contact with the end faces of the current collectors 20, 21, and the end faces and outer portions 34 of the current collectors 20, 21 are further added by the heat press 100 or the like as described above. Can be formed by heat-sealing.

  Such an electric double layer capacitor 4 has the same effects as described above. Further, in this case, since the sealing material 60 is further bonded using the end faces of the current collectors 20 and 21, the gas barrier property can be further improved and the mechanical strength of the electric double layer capacitor 4 can be sufficiently increased. Can do.

  The preferred embodiment of the present invention has been described in detail above, but the present invention is not limited to the above embodiment.

  For example, in the third to fourth embodiments, it goes without saying that the inner portion 32 and the outer portion 34 may be bonded by an adhesive.

  Further, in the above-described embodiment, a configuration suitable for the case where the present invention is applied to an electric double layer capacitor has been described. However, the present invention is not limited to an electric double layer capacitor, for example, a pseudo capacitor, a redox capacitor. It is applicable to other electrochemical capacitors.

  Furthermore, in the description of the above-described embodiment, a configuration suitable for the case where the present invention is applied to an electrochemical capacitor (particularly an electric double layer capacitor) has been described. However, the present invention is not limited to this, and lithium ion The present invention can also be applied to various secondary batteries including secondary batteries. In this case, the porous layer that becomes the first electrode (positive electrode) 12 contains an electrode active material that can be used for the positive electrode of a secondary battery such as a lithium ion secondary battery. Moreover, the porous body layer used as the 2nd electrode (negative electrode) 13 contains the electrode active material which can be used for the negative electrodes of secondary batteries, such as a lithium ion secondary battery. In this case, it is preferable to use aluminum, titanium or the like for the current collector in contact with the first electrode 12 from the viewpoint of corrosion resistance, and the current collector in contact with the second electrode 13 has a viewpoint of not forming an alloy with lithium. Therefore, it is preferable to use copper, nickel or the like.

  Next, based on an Example, the effect of this invention is demonstrated more concretely.

(Example 1)
The electric double layer capacitor of Example 1 having the same configuration as the electric double layer capacitor 1 shown in FIG.

  First, a pair of current collectors having electrodes was prepared.

As the current collector, an aluminum foil (thickness: 50 μm) cut into a predetermined rectangular shape was adopted, and electrodes were formed on these current collectors. Specifically, activated carbon (specific surface area 2000 m ² / g, BP-20 manufactured by Kuraray Chemical Co., Ltd.) 80% by weight, fluororubber (DuPont, Viton-GF) 10% by weight, conductive assistant 10% by weight of acetylene black (DENKABLACK, manufactured by Denki Kagaku Kogyo Co., Ltd.) as an agent is mixed and kneaded with a predetermined amount of methyl isobutyl ketone to form a paste, which is applied to the center of the main surface of the current collector by the metal mask method. The electrode was dried. The thickness of the electrode after drying was 50 μm. Two electrodes were prepared.

  Next, a separator was prepared. This separator was formed by cutting a paper having a thickness of 50 μm (manufactured by Nippon Kogyo Paper Industries, TF4050) larger than the area of the main surface of the electrode.

  Then, the rectangular frame-shaped sealing material like the sealing material 30 of 1st embodiment (refer FIG. 1) was prepared. First, a liquid crystal polymer sheet (Sumitomo Chemical Co., Econol, thickness 140 μm) is prepared, this liquid crystal polymer sheet is cut out along the outer shape of the current collector, and the central part is cut out into a rectangular shape. A shaped outer part was formed. Subsequently, an acid-modified high-density polyethylene sheet (thickness 140 μm) is prepared as a thermoplastic polymer sheet, cut out so as to enter the inside of the created outer portion, and the outer shape is determined, and the central portion is the size of the power generation element. A rectangular frame-shaped inner part was created by cutting out so as to correspond to.

  Subsequently, a frame-shaped inner side portion was placed so as to surround the electrode, and an outer side portion was placed so as to surround the inner side portion, on the peripheral portion of the surface on which the electrode of one current collector was formed. Then, these sealing materials were heated from the current collector side, and the inner part and one current collector were heat-sealed at 130 ° C., and the outer part and one current collector were heat-sealed at 300 ° C. Subsequently, an appropriate amount of the electrolyte solution was dropped on the electrode of the one current collector, a separator was laminated on the electrode, and an appropriate amount of the electrolyte solution was further dropped on the separator. As the electrolyte solution, a solution of triethylmethylammonium tetrafluoride salt dissolved in propylene carbonate at a concentration of 1.8 mol / L was used.

  Subsequently, an appropriate amount of the electrolyte solution was also dropped on the electrode of the other current collector. Then, the other current collector was superposed on one current collector. At this time, the electrode of the other current collector was in contact with the separator, and the peripheral portion of the other current collector was overlapped with the frame-shaped sealing material.

  Subsequently, in a vacuum atmosphere, a heat press such as the heat press 100 of the first embodiment is pressed against the current collector, the inner part of the sealing material is melted at 130 ° C., and the outer part is 300 ° C. The electric double layer capacitor was completed by melting and heat fusing. Here, ten such electric double layer capacitors were obtained.

  When the resistances of these electric double layer capacitors were measured, none of them were short-circuited, the internal resistance was 5.5 to 6.0Ω, the discharge capacity was 60 mF, and all were good products.

  Furthermore, when it stored for 1000 hours in the constant humidity tank of temperature 25 degreeC and humidity 90%, and measured the discharge capacity, they were all 58-60 mF and the capacity | capacitance retention rate was 96% or more.

(Example 2)
In Example 2, ten electric double layer capacitors were produced in the same manner as in Example 1 except that a heat press having a heat conductive member such as the heat press 150 of the first embodiment was used.

  When the resistances of these electric double layer capacitors were measured, none of them were short-circuited, the internal resistance was 5.5 to 6.0Ω, the discharge capacity was 60 mF, and all were good products.

  Furthermore, when it stored for 1000 hours in the constant humidity tank of temperature 25 degreeC and humidity 90%, and measured the discharge capacity, they were all 58-60 mF and the capacity | capacitance retention rate was 96% or more.

(Comparative Example 1)
In Comparative Example 1, ten electric double layer capacitors were obtained in the same manner as in Example 1 except that a sealing material made only of an outer portion made of liquid crystal polymer was used and the outer portion was melted at 300 ° C.

  When the resistance of these electric double layer capacitors was measured, 10 out of 10 capacitors were short-circuited.

  When these electric double layer capacitors were analyzed, it was found that the power generation element was short-circuited due to excessive heat load on the power generation element.

FIG. 1 is a cross-sectional view of the electric double layer capacitor according to the first embodiment of the present invention. FIG. 2 is a top view of the electric double layer capacitor of FIG. FIG. 3 is a table showing an example of water vapor transmission rate and oxygen transmission rate of a resin containing a liquid crystalline polymer. FIG. 4 is a table showing an example of water vapor transmission rate and oxygen transmission rate of a polymer that does not contain a liquid crystalline polymer. 5 (a) and 5 (b) are cross-sectional views illustrating a method for manufacturing the electric double layer capacitor of FIG. FIG. 6 is a cross-sectional view subsequent to FIG. 5B for explaining the method of manufacturing the electric double layer capacitor of FIG. FIG. 7 is a modification of FIG. 6 in the method for manufacturing the electric double layer capacitor of FIG. FIG. 8 is a cross-sectional view of the electric double layer capacitor according to the second embodiment of the present invention. FIG. 9 is a cross-sectional view of the electric double layer capacitor according to the third embodiment of the present invention. FIG. 10 is a cross-sectional view of an electric double layer capacitor according to the fourth embodiment of the present invention.

Explanation of symbols

  1, 2, 3, 4 ... electric double layer capacitor (electrochemical device), 10 ... power generation element, 12 ... first electrode, 13 ... second electrode, 20, 21 ... current collector, 20a, 21a ... peripheral portion, 20b, 21b ... end face, 20c, 21c ... inner surface, 30, 40, 50, 60 ... sealing material, 32 ... inner part, 34 ... outer part, 36 ... adhesive, 38 ... additional part, 104 ... high temperature heater (heating) Means), 102 ... Low temperature heater (heating means), 112 ... Heat conduction member (heating means), 114 ... Heat conduction member (heating means), 100, 150 ... Heat press.

Claims (15)

A pair of plate-like current collectors facing each other;
A first electrode, a second electrode, and an electrolyte provided between the electrodes, wherein the first electrode is in contact with one of the current collectors and the second electrode is in contact with the other current collector. A power generation element sandwiched between current collectors;
A sealing material for closing a gap between a peripheral portion of one of the current collectors and a peripheral portion of the other current collector to seal the power generating element between the current collectors,
The sealing material is
An inner portion made of a thermoplastic polymer that surrounds the power generation element and is thermally fused to the peripheral edge of one of the current collectors and the peripheral edge of the other current collector;
An outer part made of a liquid crystalline polymer that surrounds the inner part from the outside and is thermally fused to the peripheral part of one of the current collectors and the peripheral part of the other current collector,
The thermoplastic polymer is an electrochemical device having a melting temperature lower than that of the liquid crystalline polymer.   The electrochemical device according to claim 1, wherein the melting temperature of the liquid crystalline polymer is 180 to 350 ° C. The water vapor permeability of the liquid crystalline polymer is 1 g / (m ² · 24 hr · 100 µm) or less, and the oxygen permeability of the liquid crystalline polymer is 10 mL / (m ² · 24 hr · 100 µm). 2 electrochemical devices.   The electrochemical device according to claim 1, wherein the liquid crystalline polymer includes liquid crystal polyester.   The electrochemical device according to any one of claims 1 to 4, wherein a melting temperature of the thermoplastic polymer is 90 to 200 ° C.   The electrochemical device according to any one of claims 1 to 5, wherein the inner portion and the outer portion are bonded to a peripheral portion of the current collector with an adhesive strength of 0.65 N / mm or more.   The electrochemical device according to claim 1, wherein the thermoplastic polymer includes a polyolefin.   The electrochemical device according to any one of claims 1 to 7, wherein the inner portion and the outer portion are bonded with an adhesive.   The electrochemical device according to any one of claims 1 to 7, wherein the inner portion and the outer portion are thermally fused to each other.   The inner portion is a laminate in which a plurality of sub-layers having different melting temperatures are laminated in a direction approaching the power generation element, and the melting temperature of each sub-layer in the laminate decreases as the power generation element is approached. The electrochemical device according to any one of claims 1 to 9, which is configured as described above.   The electrochemical device according to any one of claims 1 to 10, wherein the outer portion is further thermally fused to an end surface of the current collector to surround the end surface of the current collector. A power generation element having a first electrode, a second electrode and an electrolyte provided between these electrodes, a pair of plate-like current collectors, and an inner side made of a thermoplastic polymer and capable of surrounding the power generation element And a sealing material made of a liquid crystalline polymer and having an outer portion that can surround the inner portion, and a melting temperature of the thermoplastic polymer is lower than a melting temperature of the liquid crystalline polymer. A preparation process;
One current collector is in contact with the first electrode of the power generation element, the other current collector is in contact with the second electrode of the power generation element, the inner portion surrounds the power generation element, and the outer portion is the An arrangement step of sandwiching the power generation element and the sealing material between the pair of plate-like current collectors in an arrangement so as to surround the inner part,
The inner part of the sealing material is heated to a first temperature to thermally fuse the inner part with the current collector, and the outer part of the sealing material is heated to a second temperature higher than the first temperature. And a heating step of heat-sealing the outer portion with the current collector.   In the heating step, the sealing member is heated by bringing the heating means into contact with the current collector, and the temperature of the portion of the heating means that faces the outer portion across the current collector is determined. The method for producing an electrochemical device according to claim 12, wherein the temperature is set higher than a temperature of a portion facing the inner portion across the current collector.   In the heating step, the sealing means is heated by bringing a heating means into contact with the current collector, the heating means is brought into contact with a portion of the current collector facing the sealing material, and the heating means is brought into contact with the current collector. The method for producing an electrochemical device according to claim 12 or 13, wherein the electric body is not brought into contact with a portion facing the power generation element.   The method for producing an electrochemical device according to any one of claims 12 to 14, wherein, in the heating step, a portion of the current collector facing the power generation element is cooled.

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