JP6103623B2 - Electrochemical cell - Google Patents

Description

  The present invention relates to an electrochemical cell, and more particularly to an electrochemical cell such as a chip-type electric double layer capacitor, ion capacitor, or nonaqueous electrolyte battery.

  An electrochemical cell such as an electric double layer capacitor, which is an electricity storage device, includes a pair of polarizable electrodes and a separator interposed between the pair of polarizable electrodes in a storage container sealed by a lid and a container body. And a pair of polarizable electrodes and an electrolytic solution impregnated in the separator. Such an electric double layer capacitor is used as a memory backup power source or a clock function backup power source in various small electronic devices such as mobile phones, PDAs, and portable game machines.

  As an electric double layer capacitor which is an electrochemical cell as described above, a disk-shaped button type is frequently used, and a rectangular chip type electric double layer capacitor has also been proposed (for example, Patent Document 1, 2).

JP 2001-216852 A JP 2012-064922 A

  Generally, in an electric double layer capacitor, an electrode made of activated carbon, a conductive auxiliary agent such as carbon black or graphite, and a binder is used as the pair of polarizable electrodes described above. And after providing the electrochemical element comprised from such a pair of electrode, a separator, etc. in the container main body for enclosing electrolyte solution, the opening part of a storage container is plugged with a cover body and welded. At this time, the electrolytic solution in the storage container is volatilized by the welding heat, and the sealing is completed in a state where the electrolytic solution is insufficient. As described above, when the electrolytic solution in the electric double layer capacitor is insufficient, the internal resistance increases due to the mechanism described below, and the charge / discharge efficiency may decrease.

Conventionally, when manufacturing an electric double layer capacitor, it is necessary to inject an electrolytic solution into the storage container before welding the lid material to the storage container. It is desirable to impregnate. In particular, since the activated carbon and the conductive additive used for the electrode have an action of sucking the electrolytic solution, the electrode swells and becomes thick. At this time, when PTFE (PolyTetraFluoroEthylene) is used as a binder at the time of forming the electrode and the amount thereof is small, an action of swelling the entire electrode by impregnation with the electrolytic solution can be obtained. Further, when PVdF (Polyvinylidene DiFluoride) or PVdF-HFP (HexaFluoroPropene) is added to the binder, an effect of swelling the electrode can be obtained.
As described above, since the electrode swells when the electrolytic solution permeates, for example, a dimensional accuracy error of each member such as a storage container made of ceramic accumulates, and sufficient adhesion between the electrode and the separator cannot be obtained. Even when such a large error occurs, it is possible to fill the gap between the electrode and the separator by absorbing this error by the swelling of the electrode. As a result, an increase in internal resistance is suppressed, and the effect of increasing charge / discharge efficiency is obtained.

  Here, in order to stably obtain the action of expanding the electrode, it is necessary that more electrolytic solution is present in the storage container. However, as described above, when the amount of the electrolytic solution is small due to volatilization due to welding heat, the amount of the electrolytic solution impregnated in the electrode is reduced, so that the electrode is difficult to expand. For this reason, in the electric double layer capacitor having the conventional configuration, even when a gap is generated between the electrode and the separator due to accumulation of dimensional accuracy error of each member, the electrode does not swell so as to fill the gap. There is a big problem that the internal resistance increases and a large current cannot be obtained, and the charge / discharge efficiency is remarkably lowered.

  The present invention has been made in view of the above problems, and even when the accumulation of the dimensional error of each member is large and the amount of electrolyte impregnation in the electrode is reduced, the gap between the electrode and the separator It is an object of the present invention to provide an electrochemical cell that can prevent a gap from being formed between an electrode and a current collector and has low internal resistance and excellent charge / discharge efficiency.

In order to solve the above problems, the electrochemical cell of the present invention is a chip that includes an electrochemical element inside a storage container in which a lid and a container body are sealed, and can be charged and discharged via an external terminal. A type of electrochemical cell, wherein the electrochemical element is disposed on the outside of the pair of electrodes disposed opposite to each other, the separator disposed between the pair of electrodes, and the pair of electrodes, respectively. A pair of current collectors joined to the storage container and electrically connected by being adjacent to the pair of electrodes, and being housed in the storage container and impregnated in the pair of electrodes and the separator And one or both of the pair of current collectors are made of a high porosity material having voids, and the voids are impregnated with the electrolyte.

  As described above, by adopting a configuration in which at least one of the pair of current collectors is made of a high porosity material having a void portion and the void portion is impregnated with an electrolytic solution, the storage container is sealed by welding. At this time, even when the electrolytic solution in the container is volatilized by welding heat, the electrolytic solution impregnated in the current collector is discharged and gradually penetrates into the electrode. As a result, the electrode is sufficiently swollen and the thickness is increased, so even if the accumulation of dimensional errors of each member is large, between the electrode and the separator and between the electrode and the current collector. The space is in close contact. Therefore, an increase in internal resistance is prevented, a large current is obtained, and charge / discharge efficiency can be improved.

In the electrochemical cell of the present invention, the high porosity material forming the pair of current collectors preferably has a porosity of 60 to 98%.
By using a material having a porosity in the above range for the current collector, the gap can be efficiently impregnated with the electrolytic solution, and the electrode is swollen by the discharge of the electrolytic solution from the gap and each member is swelled The effect of reducing the internal resistance of the electrochemical cell can be remarkably obtained by closely adhering them.

The high void material forming the pair of current collectors is preferably a metal foam body.
The foam metal body is more preferably a foam metal material of aluminum or stainless steel.
By using the above material as a high-gap material forming a pair of current collectors, a sufficient amount of electrolyte can be impregnated in the gap, and the electrodes can be swollen by the discharge of this electrolyte to allow each member to swell. By closely adhering, the effect of reducing the internal resistance of the electrochemical cell can be obtained more remarkably.

Further, the high void material forming the pair of current collectors may be a metal wire net.
The metal wire net may be made of aluminum or stainless steel.
For example, even when a metal wire net made of the above-described material is used as the high void material forming the pair of current collectors, the void portion can be impregnated with an electrolyte solution as described above. The effect of reducing the internal resistance of the electrochemical cell can be obtained by swelling the adjacent electrodes.

In the electrochemical cell of the present invention, it is more preferable that a pair of current collectors made of the foam metal body or the metal wire network is covered with a carbon material.
Thus, the effect of preventing the current collector from being corroded can be obtained by covering the pair of current collectors made of the metal foam or metal wire with the carbon material.

Further, in the electrochemical cell of the present invention, the high void material forming the pair of current collectors may be carbon paper.
Even when carbon paper is used as a high gap material forming a pair of current collectors, the internal resistance of the electrochemical cell can be obtained by impregnating the gap with an electrolyte solution and swelling the adjacent electrode with the electrolyte solution, as described above. The effect of reducing is obtained.

In the electrochemical cell of the present invention, it is preferable that the storage container and the pair of current collectors are welded.
By welding the storage container and the current collector, both members can be firmly fixed, and the effect of reducing the internal resistance of the electrochemical cell can be obtained more remarkably.

Moreover, the electrochemical cell of this invention is good also as a structure by which the said storage container and the said pair of electrical power collector are adhere | attached with the electroconductive adhesive agent.
By adopting a method in which the storage container and the current collector are fixed with a conductive adhesive, the storage container and the current collector can be used even when carbon paper is used as the high void material forming the current collector. As described above, the internal resistance of the electrochemical cell can be reduced.

The electrochemical cell of the present invention may be configured such that the electrolyte solution impregnated in the pair of current collectors flows into the pair of electrodes, and the pair of electrodes swells due to the impregnation of the electrolyte solution, whereby the separator It is preferable that a compressive load is applied to.
When a compressive load is applied by the pair of electrodes and the separator is compressed, the distance between the electrodes is shortened, so that the internal resistance can be reduced.

Further, the electrochemical cell of the present invention is more preferably provided with a paste layer made of a carbon-containing material and having a through-hole between each of the pair of current collectors and the pair of electrodes. preferable.
By providing a paste layer containing carbon between the current collector and the electrode, the contact resistance can be suppressed while securely securing the current collector and the electrode. The effect of reducing the resistance can be obtained more remarkably.

According to the electrochemical cell of the present invention, the electrolyte solution impregnated in the electrode with welding heat when sealing the storage container by welding by providing a pair of current collectors made of a high porosity material as described above. Even when the liquid is volatilized, the electrolyte impregnated in the current collector is gradually released and supplied to the electrode, so that the electrode sufficiently swells and increases in thickness. The electrolyte solution is also indirectly supplied to the separator. In addition, since the electrochemical cell is repeatedly charged and discharged, even when the electrolyte impregnated in the electrode or separator is volatilized or reduced, the electrolyte impregnated in the current collector is supplied. Is maintained in a sufficiently swollen state, and the separator is also maintained in a state sufficiently containing the electrolyte.
As a result, even if the accumulation of dimensional errors of each member constituting the electrochemical cell is large, the electrode and the separator, or the electrode and the current collector are in close contact with each other. The opposing area of the electrode through the separator increases. Further, since the pair of electrodes swell and the thickness increases, compressive stress is applied to the intervening separator, and the distance between the pair of electrodes is reduced, so that the resistance value between the electrodes is suppressed.
Accordingly, an increase in internal resistance can be prevented, a large current can be obtained, charge / discharge efficiency can be improved, and an electrochemical cell excellent in electrical characteristics can be provided.

FIG. 1 is a cross-sectional view schematically showing a nonaqueous electrolyte battery and an electric double layer capacitor which are embodiments of the electrochemical cell of the present invention.

  Hereinafter, as an embodiment of the electrochemical cell of the present invention, an embodiment of an electric double layer capacitor (non-aqueous electrolyte battery) will be given, and each of those configurations will be described in detail with reference to the drawings. The electrochemical cell described in the present invention specifically refers to an electric double layer capacitor, a nonaqueous electrolyte battery, or the like in which an active material used as a positive electrode or a negative electrode and an electrolytic solution are accommodated in a container. Also in the present embodiment, these will be described as examples.

“Electric Double Layer Capacitors (Nonaqueous Electrolyte Batteries)”
The electric double layer capacitor 1 of the first embodiment shown in FIG. 1 is a so-called chip-type capacitor having a substantially rectangular parallelepiped shape with a length of 2 to 3 mm, a width of 2 to 3 mm, and a height of 0.2 to 1 mm. The electric double layer capacitor 1 includes an electrochemical element 15 inside the storage container 2. The electrochemical element 15 includes a pair of polarizable electrodes (a pair of electrodes) 40 including a negative electrode side electrode 42 and a positive electrode side electrode 44 arranged to face each other with a separator 46 interposed therebetween. Further, a negative electrode current collector 43 and a pair of current collectors electrically connected to the pair of negative electrode side electrode 42 and positive electrode side electrode 44 are provided outside the negative electrode side electrode 42 and the positive electrode side electrode 44, respectively. Each of the positive electrode current collectors 45 is disposed. The polarizable electrode 40 and the separator 46 are impregnated with the electrolytic solution 50 stored in the storage container 2.

The storage container 2 includes a container main body 20 that stores the electrochemical element 15 and a lid 10 that is a flat sealing plate that closes the opening of the container main body 20, and the positive electrode current collector 45. Is bonded to the bottom of the container body 20, and the negative electrode current collector 43 is bonded to the inner surface side of the lid body 10. In addition, an external terminal electrically connected to the bottom wall portion 21 of the container body 20 through the negative electrode current collector 43 and the positive electrode current collector 45 between the negative electrode side electrode 42 and the positive electrode side electrode 44. 60 and 70 are provided, and charging and discharging are possible through the external terminals 70 and 60.
In the electric double layer capacitor 1 of the present embodiment, one or both of the paired negative electrode current collector 43 and positive electrode current collector 45 is made of a high porosity material having a void portion, At least when the electric double layer capacitor (electrochemical cell) 1 is assembled, the electrolytic solution 50 is impregnated.

(Storage container)
As shown in FIG. 1, the storage container 2 includes a bottomed square cylindrical container body 20, a lid 10 that is a substantially flat sealing plate that closes the opening of the container body 20, and an opening of the container body 20. A sealing ring 30 provided at the periphery is provided, and the lid body 10 and the container body 20 are sealed through the sealing ring 30. Although the thickness of the wall of the storage container 2 is not specifically limited, For example, it is 0.15-0.25 mm. Further, the shape of the lid body 10 is not limited to a substantially flat plate shape as shown in the illustrated example, and may be a convex shape or a concave shape, for example.

In the illustrated example, the container body 20 includes a flat base plate 22 having a substantially rectangular shape in plan view, and a bottom wall portion 21 including an intermediate layer 26 provided on one surface of the base plate 22, and a peripheral edge of the bottom wall portion 21. And a square cylindrical side wall portion 24 erected. In addition, at approximately the center of the intermediate layer 26, at least one conductive protective layer 27 penetrating the intermediate layer 26 is provided.
The seal ring 30 is joined to the peripheral edge of the opening of the container body 20, that is, the upper end surface 23 of the side wall 24 by a brazing material 32.

Examples of the material of the base material 22 forming the container body 20 include heat-resistant materials having insulating properties such as ceramic, glass, plastic, and alumina.
The side wall 24 is made of the same material as the base material 22. The side wall part 24 is obtained by baking the green sheet comprised, for example with ceramic, glass, an alumina.
The intermediate layer 26 is made of the same material as the base material 22. The intermediate layer 26 is made of, for example, a green sheet in the same manner as the side wall portion 24, and after the second metal layer 72 is provided on the base material 22, the second metal layer 72 is covered with ceramic, glass, alumina, or the like. It is also possible to provide the structured green sheets by stacking, that is, stacking and firing.
Examples of the protective layer 27 include conductive metals such as aluminum, tungsten, gold, and silver, or conductive resins containing carbon as a conductive filler. Among them, an aluminum vapor deposition layer and a conductive resin layer are preferable. . When the intermediate layer 26 is provided, the protective layer 27 can be provided by providing an arbitrary quantity of conductive metal, conductive resin, or the like at any position and sintering.

Moreover, as a material of the seal ring 30, the thing etc. by which nickel plating was given to Kovar etc. are mentioned.
The lid 10 and the seal ring 30 have the same linear expansion coefficient in order to prevent the sealing portion from being fragile due to the degree of expansion of the material at the time of bonding and the stress at the time of contraction caused by cooling after bonding. It is preferable to use a material. Similarly, for the seal ring 30 and the container main body 20, it is preferable to select materials having a linear expansion coefficient in order to prevent the container main body 20 from being damaged by the residual stress due to heat. Here, for example, alumina (Al ₂ O ₃ ) used as the main component of the storage container 2 has a representative value of linear expansion coefficient (400 ° C.) of 7.1 × 10 ⁻⁶ K ⁻¹ , and the lid 10 Alternatively, the Kovar used as the main component of the seal ring 30 has a representative value of linear expansion coefficient of 4.9 × 10 ⁻⁶ K ⁻¹ .
Examples of the brazing material 32 include conventionally known brazing materials such as gold brazing and silver brazing.

  As the lid 10, for example, nickel plating was applied to a conductive metal flat plate such as a nickel-iron alloy containing about 50% by mass of nickel, such as Kovar (iron, nickel and cobalt alloy) and 42 alloy. Things can be adopted. This nickel plating serves as a bonding material when welding with the seal ring 30.

In the present embodiment, it is sufficient that the negative electrode side electrode 42 is electrically connected to the lid body 10. For example, the negative electrode side electrode 42 is bonded to the lid body 10 by a negative electrode current collector 43 made of a conductive resin adhesive. Preferably it is. The positive electrode 44 in the example shown in FIG. 1 is electrically connected to the protective layer 27 by a positive current collector 45 similar to the negative current collector 43.
In addition, the heat resistance of an adhesion part can be improved by using a thermosetting resin for a conductive resin adhesive (binder). Moreover, electroconductivity can be improved by using graphite and carbon black as a conductive filler with a thermosetting resin.

  Two external terminals 60 and 70 are provided on the outer bottom surface and the outer side surface of the container body 20. The external terminal 60 is connected to a first metal layer 62 provided between the brazing material 32 and the side wall portion 24. As a result, the external terminal 60 is electrically connected to the negative electrode 42 via the first metal layer 62, the brazing material 32, the seal ring 30, the lid body 10, and the negative electrode current collector 43. The external terminal 70 is connected to a second metal layer 72 provided between the base material 22 and the intermediate layer 26 and connected to the protective layer 27. Accordingly, the external terminal 70 is electrically connected to the positive electrode 44 via the second metal layer 72, the protective layer 27, and the positive electrode current collector 45.

The external terminal 60 is a flat plate or thin film made of a conductive metal such as nickel or gold, and is provided by, for example, conductor printing on the container body 20 and firing. It is preferable that a weld layer of nickel, gold, solder, or the like is provided on the surface of the external terminal 60 so as to be welded onto the substrate. This weld layer can be mainly provided by a plating method (wet method), but a vapor phase method (dry method) such as vapor deposition may be used.
The external terminal 70 is the same as the external terminal 60.

The first metal layer 62 is a flat plate or thin film of a conductive metal such as tungsten, nickel, gold, silver, and is provided by, for example, printing the metal on a green sheet and baking it. Among these, the first metal layer 62 is preferably tungsten.
The second metal layer 72 is the same as the first metal layer 62.

(electrode)
As the negative electrode side electrode 42, for example, a powdery activated carbon obtained by performing an activation treatment using an organic substance such as sawdust, coconut shell, pitch, coke, phenol resin or the like alone or in combination with water vapor or alkali is used as a binder. A rolling roll or a press-molded one is also included. Also, for example, phenol, rayon, acrylic, pitch, etc. fibers are infusibilized and carbonized to form activated carbon or activated carbon fibers, which are made into a felt, fiber, paper, or sintered body. You may use what you did.

The density of the negative electrode side electrode 42 is not particularly limited, but is preferably ^{0.1~0.9g / cm 3, 0.40~0.75g / cm} 3 is more preferable. When the density of the negative electrode side electrode 42 is less than 0.1 g / cm ³ , the energy density of the negative electrode side electrode 42 decreases, and when the negative electrode side electrode 42 expands due to impregnation with the electrolytic solution 50, There is a risk that the electrical resistance increases as the distance increases. On the other hand, when the density of the negative electrode side electrode 42 is more than 0.9 g / cm ³ , not only a great pressure is required when forming the negative electrode side electrode 42 but also the amount of impregnation of the electrolytic solution 50 into the negative electrode side electrode 42. Is significantly reduced.

The activated carbon that is the active material of the negative electrode 42 can have various pore distributions and surface states depending on the starting material, carbonization method, or activation conditions. Among the activated carbons having such various surface states and pore distributions, the specific surface area of the activated carbon used for the active material of the negative electrode 42 is preferably 1000 m ² / g or more, more preferably 1700 m ² / g or more, and 2400 m. ² / g or more is more preferable. If it is 1000 m <2> / g or more, sufficient electrostatic capacity can be obtained.
The pore volume of the activated carbon is preferably from 0.4 cm ³ / g or more, 0.7 cm ³ / g or more is more preferable. If the pore volume of the activated carbon is 0.4 cm ³ / g or more, sufficient electrostatic capacity can be obtained.
Further, the pores of the activated carbon are the ratio (fine pore ratio) of the pores having a pore radius of less than 1 nm in the total pores (number of pores having a pore radius of less than 1 nm) / (total number of pores). Is preferably 75% or less, more preferably 50% or less, and still more preferably 30% or less. This is because if this value is 75% or less, a sufficient capacitance can be obtained.
Further, the pores of the activated carbon are the ratio of the pores having a pore radius of 1 to 3 nm to the total pores (medium pore ratio) (the number of pores having a pore radius of 1 to 3 nm) / (total pores). The value represented by the number) is preferably 20% or more, more preferably 50% or more, and still more preferably 70% or more. If this value is 20% or more, sufficient electrostatic capacity can be obtained, and if it is 70% or more, it is prevented from deterioration by continuous application of a high voltage of 3 V or more by combination with the electrolytic solution 50 containing cyclic sulfone. The performance is further improved.

  As the binder, conventionally known substances can be used. For example, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), styrene butadiene Examples thereof include rubber (SBR), polyimide, etc. Among them, a fluorine-based binder is preferable, and PTFE and PVDF are most preferable. Any one of PTFE, PVDF, and PVDF-HFP can be used alone, or a plurality of kinds can be mixed at an arbitrary ratio and used simultaneously. For example, the content of the binder in the negative electrode 42 is preferably 2 to 14% by mass, and more preferably 4 to 12% by mass from the viewpoint of improving durability and handling properties during production. The blending ratio of the fluorine-based binder is preferably 8% by mass or less.

A conductivity-imparting agent (conducting aid) can be added to the negative electrode 42. Examples of the conductivity imparting agent include amorphous carbon such as carbon black such as furnace black, channel black, acetylene black, and thermal black, carbon fiber (CF), carbon nanohorn (CNH), and carbon nanotube, depending on the production method. Examples thereof include crystalline carbonaceous materials such as (CNT) and powdered graphite, and metal powders having high corrosion resistance such as SUS and Ti.
90/4 or less is preferable, as for the compounding ratio (activated carbon / conductive aid) of activated carbon and a conductive support agent, 70/24 or less is more preferable, and 50/44 or less is especially preferable.
When the blending ratio of the binder is reduced, it is necessary to apply sufficient shear to the PTFE of the binder to stretch the PTFE into a thread shape and entangle it with the activated carbon particles. Therefore, as the conductive auxiliary agent, carbon black that can maintain the structure structure of carbon black even when sufficient shearing is applied, and oil furnace black having a hollow shell structure is particularly desirable.

As the conductive assistant, it is desirable to use a mixture of graphite having high crystallinity and carbon black having low crystallinity. Although graphite has a large particle size, its own electronic conductivity is high. Carbon black has a smaller particle diameter, although it has lower electronic conductivity than graphite. Carbon black with a small particle diameter can enter the gaps in the electrode material and reduce the resistance of the entire electrode. Therefore, the resistance value can be optimized by mixing graphite and carbon black as a conductive aid. Graphite is desirably added in an amount of 20 wt% or more and 60 wt% or less.
Among carbon blacks, it is desirable to employ furnace black having a hollow shell-like structure with excellent electrode expansion action.

As the positive electrode side electrode 44, the same thing as the negative electrode side electrode 42 is mentioned.
The negative electrode side electrode 42 and the positive electrode side electrode 44 may have the same configuration or may be different, and can be determined in consideration of the type of the supporting salt and the like. Here, when the applied voltage at the time of charging of the electric double layer capacitor 1 is high, cations in the supporting salt are adsorbed on the negative electrode 42 and decomposed on the electrode surface, and the concentration in the electrolytic solution 50 is reduced. It will be a thing. As the concentration of the supporting salt decreases, the discharge capacity of the electric double layer capacitor 1 decreases. Similarly, the anion in the supporting salt is adsorbed on the positive electrode 44 and decomposed on the electrode surface, and the concentration in the electrolytic solution 50 is lowered. As the concentration of the supporting salt decreases, the discharge capacity of the electric double layer capacitor 1 decreases.

(Current collector)
In the electric double layer capacitor 1 of the present embodiment, as a pair of current collectors that are respectively disposed outside the negative electrode 42 and the positive electrode 44 that are a pair of electrodes and are electrically connected to these electrodes, A negative electrode current collector 43 and a positive electrode current collector 45 are provided.

The negative electrode current collector 43 is disposed on the negative electrode side electrode 42 side as in the example illustrated in FIG. 1, and the container body 20 is interposed via the lid body 10, the seal ring 30, the brazing material 32, and the first metal layer 62. Are electrically connected to external terminals 60 provided on the external bottom surface and the external side surface.
The positive electrode current collector 45 is disposed on the positive electrode side electrode 44 side, and is electrically connected to an external terminal 70 provided on the outer bottom surface of the container body 20 via the protective layer 27 and the second metal layer 72. Has been.

In the present invention, one or both of the negative electrode current collector 43 and the positive electrode current collector 45 are made of a high porosity material having a void portion, and the void portion is impregnated with the electrolytic solution 50.
As the high porosity material used for the negative electrode current collector 43 or the positive electrode current collector 45, it is preferable to use a foam metal body (also referred to as a porous metal), for example, a foam metal material of aluminum or stainless steel. it can.

  Examples of the metal foam material made of aluminum include foamed aluminum (porous aluminum: registered trademark; manufactured by Mitsubishi Materials Corporation), aluminum cermet (aluminum porous body: registered trademark; manufactured by Sumitomo Electric Industries, Ltd.), and the like. be able to. The foamed aluminum (registered trademark) is a sheet-like material obtained by mixing aluminum powder with a foamed material and foaming, followed by firing. The above-mentioned aluminum cermet (registered trademark) is obtained by plating a foamed polystyrene material with aluminum and then firing the foamed polystyrene material while sublimating it.

  In addition, as the foam metal material made of stainless steel, a commercially available foam metal material (for example, a foam metal manufactured by Mitsubishi Materials Corporation) can be used without any limitation.

Examples of the metal foam material include raw powder, a water-soluble resin binder, a foaming agent that is a water-insoluble hydrocarbon-based organic solvent, a surfactant that is added as necessary, and the balance. It may be obtained by a production method (slurry foaming method (powder sintering method)) in which a foamed slurry formed by mixing water and inevitable impurities is used as a raw material. Alternatively, it may be a foam metal material obtained by a method (plating method) in which the urethane foam is subjected to a conductive treatment and then plated, and if necessary, is subjected to a heat treatment.
In addition to the method described above, a method for producing a foam metal material (porous metal) includes a molten metal gas injection method (CL), a melt foam method (CL), a hollow metal sintering method (OP / CL), a half Examples thereof include a melt foaming method (precursor method) (CL), a gas expansion method (CL), and a continuous zone melting method (CL). However, when these methods are used, the metal porous portion is finished in a closed system, so that the effect of supplementing the electrolyte solution to the electrode is poor because it contains an electrolyte solution beforehand. It is preferable to use a plating method.
Furthermore, as a high porosity material used for each current collector, two or more types of foam metal materials having different hole diameters may be used in combination, and a material having high bending strength is preferably used.

  Further, in the present embodiment, as a high porosity material used for the negative electrode current collector 43 and the positive electrode current collector 45, a metal wire network can be employed instead of the above foam metal material, for example, aluminum Or the metal wire net | network which consists of stainless steel can be mentioned. Specifically, the metal wire net is a net produced by knitting a metal wire made of the above-mentioned material, and in addition, an expanded metal or a punching metal (hole shape: round hole, slit, ribbon, It also includes a sintered body of chatter metal such as a square hole, a slit bay screen) and an etching foil.

  Moreover, in this embodiment, you may employ | adopt the structure by which the negative electrode current collector 43 and the positive electrode current collector 45 which consist of a foam metal body or a metal wire net | network as mentioned above were coat | covered with the carbon material. By covering the negative electrode current collector 43 and the positive electrode current collector 45 with a carbon material, specifically, a conductive carbon paste, each current collector can be prevented from corroding.

  Furthermore, in the present embodiment, paper-like carbon paper is adopted as the high porosity material used for the negative electrode current collector 43 and the positive electrode current collector 45 in place of the foam metal body and the metal wire network. You can also As such carbon paper, for example, carbon paper TGP-H-030 (product name: registered trademark; manufactured by Toray Industries, Inc.) can be used, but commercially available carbon felt and carbon cloth can also be used. Is possible.

As carbon paper which is a high porosity material, in the case of carbon paper produced by binding short fibers with a binder, those having short fibers of 10 mm or more can be used. Further, as described above, a carbon cloth made of a woven fabric composed of a weft and a warp formed by aggregating a plurality of carbon fibers can be used as the high porosity material.
As described above, when carbon paper, carbon felt, carbon cloth or the like is used as the high porosity material, the purity of the carbon material is preferably 85% or more, and the density is 1.72 to A range of 2.1 g / cc is preferable. The carbon fiber diameter is preferably in the range of 1 to 20 μm.
In addition, when a carbon cloth composed of wefts and warps is used, the density of the wefts and warps is preferably 15 to 25 yarns / cm, and the density of the carbon material is 8 to 200 g / m ² . It is preferably 80 to 200 g / m ² . Further, the thickness of the carbon material without load is preferably 180 to 450 μm, more preferably 280 to 400 μm. Further, as the fabric, a flat knitting, a milling knitting, a Kanoko knitting or the like can be used, but in this embodiment, a flat knitting is preferable.

  On the other hand, when carbon paper is used for the negative electrode current collector 43 or the positive electrode current collector 45, since bonding with other members cannot be performed by welding, the carbon paper is bonded with a conductive adhesive or the like. From the viewpoint of bondability, it is most preferable to use a metal material such as the above-mentioned foam metal body or metal wire network.

  In this embodiment, regarding the high porosity material used for the negative electrode current collector 43 or the positive electrode current collector 45 as described above, the porosity is preferably in the range of 60 to 98%. If the porosity of the high porosity material is in the above range and a high porosity is ensured, it is possible to efficiently impregnate the cavity with a sufficient amount of the electrolytic solution 50. When the porosity of the high porosity material forming each current collector is less than 60%, the electrolyte solution 50 cannot be impregnated in a sufficient amount. Further, the porosity of the high porosity material is superior in terms of the amount of the electrolyte solution 50 impregnated, but it is difficult to produce a high porosity material with a porosity exceeding 98%. This is the upper limit.

  The negative electrode current collector 43 and the positive electrode current collector 45 preferably have a thickness in the range of 0.04 to 1 mm before assembly. In addition, after assembling the negative electrode current collector 43 and the positive electrode current collector 45, the thickness of the electric double layer capacitor 1 in a completed state is preferably in the range of 0.05 to 0.4 mm. Usually, each current collector after completion as the electric double layer capacitor 1 is in a state where the thickness is slightly reduced by compression. By setting the thickness before assembly of the negative electrode current collector 43 and the positive electrode current collector 45 and the thickness after being completed as the electric double layer capacitor 1 within the above range, each current collector is within a predetermined compression ratio range. It is suppressed to a minimum that the porosity of the high-porosity material forming the above is reduced by compression. As a result, a sufficient amount of the electrolyte solution 50 impregnated in the negative electrode current collector 43 and the positive electrode current collector 45 can be ensured. For example, when the storage container 2 is sealed by welding, the welding heat Even when the electrolytic solution 50 impregnated in each electrode volatilizes, the electrolytic solution 50 impregnated in the negative electrode current collector 43 and the positive electrode current collector 45 is gradually released, and the negative electrode side electrode 42 and the positive electrode side It is supplied to the electrode 44. And since the electrolyte solution 50 impregnates the negative electrode side electrode 42 and the positive electrode side electrode 44 and each electrode fully swells and the thickness increases, for example, even when the accumulation of dimensional error of each member is large, etc. Since the electrode-separator and the electrode-current collector are sufficiently in close contact with each other and the opposing area of each electrode through the separator 46 is increased, the contact resistance between the members is reduced. Further, since the negative electrode 42 and the positive electrode 44 swell and increase in thickness, the interstitial separator 46 is compressed by applying compressive stress, and the distance between the electrodes is reduced. The value is suppressed.

  Further, in the present embodiment, by using a high porosity material for the negative electrode current collector 43 and the positive electrode current collector 45, a sufficient amount of the electrolytic solution 50 can be impregnated in the void portion. There is no need to provide a gap filled with the liquid 50. In this case, since there is room in the internal space of the storage container 2, it is possible to design a large size in plan view of the negative electrode 42 and the positive electrode 44 in advance. That is, even if the volume of the negative electrode 42 and the positive electrode 44 is the same, the facing area between the electrodes can be secured large, so that a large current can be obtained.

In addition, in the present embodiment, since the electrolytic solution 50 is indirectly supplied also to the separator 46 via the negative electrode 42 and the positive electrode 44, the electric double layer capacitor 1 is repeatedly charged and discharged. Even when the electrolyte impregnated in the electrode or separator 46 is volatilized / decreased, the electrolyte 50 discharged from the current collector is supplied to maintain each electrode in a sufficiently swollen state. At the same time, the separator 46 is maintained in a state of sufficiently containing the electrolytic solution 50.
Therefore, an increase in internal resistance is prevented, a large current is obtained, charging / discharging efficiency is improved, and excellent electrical characteristics are obtained.

  In the present embodiment, regarding the various high porosity materials as described above, it is most preferable to employ a foam metal material in consideration of the porosity and the through holes. The foam metal material has a three-dimensional network structure such as sponge, and has a very high porosity, so when applied to the negative electrode current collector 43 and the positive electrode current collector 45, Can ensure a high impregnation amount of the electrolytic solution 50 and liquid permeability.

In this embodiment, when the negative electrode current collector 43 and the positive electrode current collector 45 are made of a metal material such as a foam metal material or a metal wire net, the container 2 and each current collector are welded. It is preferable. Specifically, it is preferable that the negative electrode current collector 43 and the lid 10 are welded and the positive electrode current collector 45 and the intermediate layer 26 are welded. As a welding method in this case, for example, resistance welding, ultrasonic welding, laser welding, or the like can be used.
As described above, by welding between the storage container 2 and each current collector, a high bonding force is exhibited, and the contact resistance between the storage container 2 and each current collector is reduced, which is good. Electrical characteristics can be obtained.

Moreover, in this embodiment, between the storage container 2 and each collector may be fixed with the conductive adhesive. In particular, when the negative electrode current collector 43 and the positive electrode current collector 45 are made of carbon paper or the like, since it is difficult to perform welding, a configuration in which the storage container 2 is joined by a conductive adhesive is used. can do.
On the other hand, when considering the bonding force, contact resistance, and the like between the storage container 2 and each current collector, it is preferable to employ a configuration in which these are welded.

(Separator)
The separator 46 is interposed between the positive electrode 44 and the negative electrode 42, and an insulating film having high ion permeability and mechanical strength is used. Examples of the separator 46 include glass fiber laminates (glass fiber laminates) such as borosilicate glass, alkali glass, quartz glass, lead glass, soda lime silica glass, and alkali-free glass, polyphenylene sulfide, polyether ether ketone, and the like. And non-woven fabric made of a resin, cellulose, and a microporous film of polytetrafluoroethylene (PTFE). In the present embodiment, among these materials, a glass fiber laminate is preferable, a fiber laminate of borosilicate glass, alkali glass, and quartz glass is more preferable, and an alkali glass fiber laminate is more preferable. Such a glass fiber laminate is excellent in mechanical strength and has a large ion permeability, so that it is possible to reduce internal resistance and improve discharge capacity.

  As the glass fiber laminate, for example, glass fibers may be bonded together with a binder and integrated as a whole, and a gap may be formed. The glass fiber laminate is formed of a mixture of glass fibers (glass fibers) and a binder into an arbitrary shape and heated in a temperature range of, for example, 25 to 327 ° C. The melting point of PTFE used for the binder of the electrode (327 C.) may be subjected to a heat treatment performed below.

  The separator 46 preferably contains no impurities as much as possible, and particularly preferably does not contain a metal such as cadmium, manganese, zinc, copper, nickel, chromium, and iron. The content of each metal as an impurity in the separator 46 is less than 1 μg / g cadmium, less than 0.5 μg / g manganese, less than 5 μg / g zinc, less than 4 μg / g copper, less than 1 μg / g nickel, Chromium is preferably less than 1 μg / g and iron is less than 25 μg / g.

  The glass fiber constituting the glass fiber laminate preferably has a plurality of fiber diameters of 10 μm or less, and more preferably 1 μm or less. If the fiber diameter is 10 μm or less, when laminating the fibers, the size of each void formed in the separator 46 can be reduced, and the impregnation of the electrolyte solution 50 into the separator 46 by capillary action is more effective. Become quick. In addition, since the liquid retention of the separator 46 is increased and the ionic conductivity between the electrodes can be reduced, the resistance in the electric double layer capacitor 1 can be further reduced.

In addition, the glass fibers constituting the glass fiber laminate may be a mixture of glass fibers having a fiber diameter of more than 0.5 μm and 1.0 μm or less and glass fibers having a fiber diameter of 0.5 μm or less. In this case, it is preferable that a glass fiber contains 80 mass% or more of glass fibers with a fiber diameter of 0.5 μm or less. By containing 80% by mass or more of glass fiber having a fiber diameter of 0.5 μm or less, the electrolyte solution 50 can be more easily impregnated into the separator 46 and the resistance between the electrodes can be further reduced.
Further, the mass per unit area (hereinafter referred to as unit mass) of the glass fiber laminate is preferably 24 g / m ² or less, and more preferably 16 g / m ² or less.

  The thickness of the separator 46 is not particularly limited, but is preferably 10 μm or more and 300 μm or less in an uncompressed state before assembly. In particular, the thickness of the separator 46 is preferably 50 μm or more and 200 μm or less, more preferably 150 μm or less, and still more preferably 100 μm or less. The thickness of the separator 46 before compression is preferably equal to or less than the thickness (for example, 200 μm) of the negative electrode side electrode 42 and the positive electrode side electrode 44 that have expanded by sucking the electrolytic solution.

  In the present invention, the positive electrode 44 and the negative electrode 42 paired via the separator 46 are impregnated with the electrolytic solution 50 and swell, and the thickness of each of these electrodes increases, so that the separator 46 is compressed. Can be provided and compressed. At this time, in the present invention, the electrolyte solution 50 impregnated in the pair of negative electrode current collector 43 and the positive electrode current collector 45 flows out from each current collector, and the electrolyte solution 50 is discharged from the negative electrode side electrode 42 and the positive electrode side. By flowing into the electrode 44, a configuration in which a compressive load is applied to the separator 46 can be obtained. Thus, the separator 46 is compressed and the interelectrode distance between the negative electrode side electrode 42 and the positive electrode side electrode 44 is shortened, so that the interelectrode resistance is reduced and the internal resistance is suppressed. . Here, the thickness between the electrodes at the position compressed by each electrode is preferably 5 to 40 μm, more preferably 10 to 20 μm. Here, if the interelectrode thickness in the separator 46 is less than 5 μm, the separator function for separating the negative electrode 42 and the positive electrode 44 may be impaired. On the other hand, if the thickness between the electrodes in the separator 46 is more than 40 μm, the resistance between the electrodes increases, and the charge / discharge characteristics may be deteriorated due to an increase in internal resistance.

(Electrolyte)
The electrolytic solution 50 used in the electric double layer capacitor 1 of the present embodiment is not particularly limited. For example, a supporting salt can be dissolved in a nonaqueous solvent. In this case, the non-aqueous solvent may contain a cyclic carbonate or a cyclic sulfone as a main solvent. The cyclic carbonate can contain at least propylene carbonate (PC) and ethylene carbonate (EC). Thus, the resistance value of electrolyte solution can be reduced by containing PC and EC with a high dielectric constant (conductivity). Furthermore, in this embodiment, a derivative of cyclic carbonate can be used for the electrolytic solution. As the cyclic sulfone, at least sulfolane (SL) and derivatives thereof can be used.

  In addition, when PC or EC is contained in the electrolytic solution as a cyclic carbonate, the applied voltage is preferably set to 3.1 V or less, depending on the activated carbon used as the electrode material. In addition, the non-aqueous solvent can contain one or more kinds of symmetrical or asymmetrical chain carbonates as a sub-solvent, and those having a short aliphatic chain are particularly preferable. Ethylene carbonate (MP = about 40 ° C.) that is solid at room temperature (25 ° C.) can be handled as a solution even at room temperature by mixing with a symmetrical chain carbonate (for example, dimethyl carbonate (DMC)). Electrolytic solution 50 in which a suitable supporting salt is dissolved in such a nonaqueous solvent can be impregnated into polarizable electrode 40 and separator 46.

  When the electrolyte contains sulfolane (SL) as a cyclic sulfone, the applied voltage can be set to 3.1 V or more depending on the activated carbon used as the electrode material. In that case, the non-aqueous solvent can be configured to contain one or more types of symmetric or asymmetric chain sulfone as a sub-solvent, and an asymmetric chain sulfone having a short aliphatic chain is particularly preferable. Sulfolane (MP = about 40 ° C.) having a high viscosity at room temperature (25 ° C.) can be handled as a solution even at room temperature by mixing with asymmetrical chain sulfone (for example, ethyl methyl sulfone (EMS)). Furthermore, the negative electrode 42, the positive electrode 44, and the separator 46 can be impregnated with the electrolytic solution 50 in which an appropriate supporting salt is dissolved in such a nonaqueous solvent.

  The amount of the electrolytic solution 50 in the storage container 2 is not particularly limited, and can be appropriately determined in consideration of the container size, element characteristics, and the like. On the other hand, in the present invention, as described above, the negative electrode current collector 43 and the positive electrode current collector 45 are made of a high porosity material, and the electrolytic solution 50 is impregnated in the voids. The electrolyte 50 can be supplied to the positive electrode 44 and the negative electrode 42 by being discharged from the electric body. Therefore, in the present invention, the electrochemical element 15 is designed while maximally utilizing the space in the storage container 2 without providing a space in the storage container 2, that is, a storage space for directly storing the electrolytic solution 50. It becomes possible.

  The content of the cyclic carbonate or cyclic sulfone in the non-aqueous solvent can be determined in consideration of the heating conditions in the preheating step or the sealing step in the production of the electric double layer capacitor 1, the heating conditions in use, etc. 25-90 mass% is preferable, 50-80 mass% is more preferable, 55-70 mass% is further more preferable. When it is less than 25% by mass, the viscosity of the electrolytic solution 50 is increased and the fluidity is lowered. For this reason, for example, the injection amount of the electrolytic solution 50 varies, the remaining amount of the electrolytic solution 50 becomes unstable, and it may be difficult to obtain the electric double layer capacitor 1 having a stable quality. Further, if the content of the cyclic carbonate or cyclic sulfone in the non-aqueous solvent is more than 90% by mass, the amount of the supporting salt in the non-aqueous solvent becomes insufficient, and the discharge capacity of the electric double layer capacitor 1 cannot be secured sufficiently. There is a fear. In addition, when the content of the cyclic carbonate or cyclic sulfone exceeds 90% by mass, the content of the chain carbonate or the supporting salt becomes insufficient, and the discharge capacity under a low-temperature environment (−20 ° C. or less) can be ensured. It can be difficult.

  The content of the chain carbonate or the chain sulfone in the non-aqueous solvent can be determined in consideration of the heating condition in the preheating step or the sealing step in the production of the electric double layer capacitor 1, the heating condition in use, For example, 10-80 mass% is preferable and 10-50 mass% is more preferable. When the content of the chain carbonate in the non-aqueous solvent is less than 10% by mass, the viscosity of the non-aqueous solvent is remarkably increased and the fluidity becomes insufficient. For example, it becomes difficult to inject the electrolytic solution 50 There is. For this reason, the amount of the electrolytic solution 50 becomes insufficient, and the performance of the electric double layer capacitor 1 cannot be secured sufficiently, and it is difficult to obtain the electric double layer capacitor 1 with stable quality. Further, when the content of the chain carbonate is more than 60% by mass, the solvent added at the time of sealing is volatilized, the cyclic carbonate and the cyclic sulfone component of the remaining electrolytic solution are reduced, and the amount of the electrolytic solution 50 is reduced. Insufficient performance of the electric double layer capacitor 1 cannot be ensured sufficiently, and it may be difficult to obtain the electric double layer capacitor 1 with stable quality.

  The total amount of the cyclic carbonate and the chain carbonate in the non-aqueous solvent, or the total amount of the cyclic sulfone and the chain sulfone is the heating condition in the preheating step or the sealing step in the production of the electric double layer capacitor 1, For example, 40 to 90% by mass is preferable, 65 to 90% by mass is more preferable, and 75 to 85% by mass is more preferable. When the total amount is less than 40% by mass, the viscosity of the electrolytic solution 50 is increased and the fluidity is lowered. For this reason, for example, the injection amount of the electrolytic solution 50 varies, the remaining amount of the electrolytic solution 50 becomes unstable, and it may be difficult to obtain the electric double layer capacitor 1 having a stable quality. Moreover, when the total amount is more than 90% by mass, the amount of the supporting salt in the non-aqueous solvent becomes insufficient, and the discharge capacity of the electric double layer capacitor 1 may not be sufficiently secured. In addition, when the total amount is more than 90% by mass, the content of the supporting salt becomes insufficient, and it may be difficult to ensure the discharge capacity under a low temperature environment (−20 ° C. or lower).

  The content ratio of the cyclic carbonate and the chain carbonate in the non-aqueous solvent or the content ratio of the cyclic sulfone and the chain sulfone increases the heat resistance as the cyclic carbonate or the cyclic sulfone increases. Or when there are few cyclic | annular sulfones, it is necessary to consider that resistance rises by the fall of ionic conductivity. Therefore, the content ratio can be determined in consideration of heating conditions, usage conditions, and the like in the production of the electric double layer capacitor 1, for example, cyclic carbonate: chain carbonate = 1: 9 to 9: 1 (mass ratio). Preferably, 5: 5 to 9: 1 is more preferable, and 7: 3 to 9: 1 is more preferable.

Examples of the supporting salt include a quaternary ammonium salt and a quaternary phosphonium salt. Examples of the quaternary ammonium salt include a compound having only an aliphatic chain, an alicyclic compound having an aliphatic chain and an alicyclic ring, or a fatty acid. Examples include spiro compounds having only a ring. A spiro compound is one in which two rings share one atom of a tetrahedral structure.
Examples of the counter ion constituting the salt include PF ₆ ⁻ , BF ₄ ⁻ , N (CF ₃ SO ₃ ) ₂ ⁻ , C (CF ₃ SO ₃ ) ₃ ^{− and the} like.

Among the quaternary ammonium salts as described above, examples of the compound having only a fatty chain include triethylmethylammonium (TEMA) salt and tetraethylammonium (TEA) salt. Examples of the spiro compound include 5-azonia spiro [4,4] nonanetetrafluoroborate (spiro- (1,1 ′)-bipyrrolidinium: SBP-BF4), 6-azoniaspiro [5,5] undecanetetrafluoroborate, 3 -Azonia spiro [2, 6] nonane tetrafluoroborate, 4-azonia spiro [3, 5] nonane tetrafluoroborate, etc. are mentioned. Further, examples of the quaternary phosphonium salt include 5-phosphonspiro [4,4] nonanetetrafluoroborate.
As the supporting salt, a quaternary ammonium salt is preferable, a spiro compound is more preferable, and 5-azonia spiro [4,4] nonanetetrafluoroborate is more preferable. Since the quaternary ammonium salt spiro compound has high electrical conductivity, the discharge capacity can be increased.

The content of the supporting salt in the electrolytic solution 50 can be determined in consideration of the type of the supporting salt. For example, when the supporting salt is SBP-BF ₄ , the content of the supporting salt in the electrolytic solution 50 at the time of injection is included. The amount is preferably 1.0 to 3.6 mol / dm ³ , more preferably 1.5 to 3.6 mol / dm ³ . When the content of the supporting salt in the electrolytic solution 50 is less than 1.0 mol / dm ³ , the electrolytic solution 50 is significantly deteriorated when charged at a voltage exceeding 2.9 V, and the discharge capacity is reduced in a short period. It becomes easy. On the other hand, if the content is more than 3.6 mol / dm ^{3, the} amount of SBP-BF ₄ dissolved in the non-aqueous solvent is saturated, which may cause problems in production such as nozzle clogging.

Further, the non-aqueous solvent and the supporting salt evaporate during preheating or sealing after the electrolytic solution 50 is generated. At this time, the cyclic carbonate, the chain carbonate, the cyclic sulfone, the chain sulfone, and the arbitrary solvent in the non-aqueous solvent evaporate more easily than the supporting salt. Therefore, in the electrolytic solution 50 in the electric double layer capacitor 1 of the final product. The content of supporting salt increases. For this reason, the content of the supporting salt in the electrolytic solution 50 to be filled is determined so that the content of the supporting salt in the electrolytic solution 50 in the electric double layer capacitor 1 of the final product is in consideration of the type of the non-aqueous solvent. Preferably, it may be adjusted to 1.0 to 3.6 mol / dm ³ , more preferably 1.5 to 3.6 mol / dm ³ .

  The supporting salt decomposes and decreases when a voltage is applied to the electric double layer capacitor 1. For this reason, in applications where a high voltage is applied, the supporting salt may be in an excessive (supersaturated) state. Alternatively, the supporting salt in the electrolytic solution 50 sealed in the storage container 2 may be temporarily precipitated without being dissolved after passing through the supersaturated state depending on the subsequent preheating or heating conditions at the time of sealing. . At this time, the electrolyte 50 has a high solubility in a low-temperature environment because the solubility of the supporting salt changes depending on the supersaturated supporting salt and decomposition products, and the supporting salt is redissolved to increase the concentration of the supporting salt. Discharge capacity can be secured. Thus, the supporting salt can be replenished by bringing the supporting salt into a supersaturated state.

  The electrolytic solution 50 is, for example, a cyclic carbonate and a chain carbonate, or a cyclic sulfone and a chain sulfone, and optionally mixed with an arbitrary solvent to form a non-aqueous solvent, and a supporting salt is added to the non-aqueous solvent and stirred. And can be prepared by dissolving.

(Paste layer)
In the present embodiment, further, between each of the pair of current collectors and the pair of electrodes, that is, between the negative electrode side electrode 42 and the negative electrode current collector 43, and between the positive electrode side electrode 44 and the positive electrode current collector 45. More preferably, a paste layer (not shown) made of a carbon-containing material is provided therebetween. Thus, by providing a layer made of a conductive paste containing carbon between each pair of current collectors and each pair of electrodes, the bonding force between each electrode and each current collector is increased. While being raised, the effect that contact resistance is suppressed and internal resistance is reduced is acquired.

  Here, in the electric double layer capacitor 1 of the present embodiment, when the paste layer having the above configuration is provided, detailed illustration is omitted, but it is necessary to have a through hole in the thickness direction. This is because the electrolytic solution 50 can be circulated in order to efficiently supply the electrolytic solution 50 released from the negative electrode 42 and the positive electrode collector 45 made of a high porosity material as described above to each electrode. This is because the through hole (void) is indispensable.

  As the paste layer made of the carbon-containing material, a conventionally known carbon-containing conductive adhesive or the like can be used without any limitation. For example, the paste layer includes a thermosetting resin such as polyimide and also includes carbon. Things. By providing a paste layer made of such a carbon-containing material between each electrode and each current collector, the bonding force between them is improved, especially even when exposed to a high temperature environment. And the like can be prevented. Therefore, it is possible to suppress an increase in the contact resistance between the negative electrode 42 and the negative electrode current collector 43 and between the positive electrode 44 and the positive electrode current collector 45, and the internal resistance of the electric double layer capacitor 1 can be suppressed. Can be kept low.

  In addition, as a thickness of a paste layer, it is preferable to set it as the grade of the range of 3-100 micrometers, for example. If the thickness of the paste layer is 3 μm or less, the strength at the time of bonding may be lowered, and further, when stainless steel is used as the high-voidage material, the contact resistance may be increased. On the other hand, if the thickness of the paste layer exceeds 100, it may be necessary to reduce the thickness of the positive electrode side electrode 44 or the negative electrode side electrode 42 due to the size or the like in the storage container 2. Capacity may be reduced.

According to the electric double layer capacitor (non-aqueous electrolyte battery) 1 of the present embodiment, in particular, the container 2 is sealed by welding by including the negative electrode current collector 43 or the positive electrode current collector 45 made of a high porosity material. Even when the electrolytic solution 50 in the storage container 2 is volatilized by the welding heat at the time of welding, the electrolytic solution 50 impregnated in the current collector is gradually released, and the negative electrode 42 and the positive electrode 44 are discharged. Supplied. Thereby, the negative electrode side electrode 42 and the positive electrode side electrode 44 are sufficiently swollen to increase the thickness, and in addition, the electrolytic solution 50 is indirectly supplied to the separator 46 via these electrodes. Moreover, even if the electrolytic solution 50 impregnated in each of the electrodes and the separator 46 is volatilized / decreased due to repeated charging / discharging of the electric double layer capacitor 1, the negative electrode current collector 43 and the positive electrode current collector 45. Since the electrolyte solution 50 impregnated is supplied, the state in which each electrode is sufficiently swollen is maintained, and the state in which the separator 46 sufficiently contains the electrolyte solution 50 is maintained. Accordingly, even if the accumulation of dimensional errors of the members constituting the electric double layer capacitor 1 is large, the gap between the electrodes and the separator 46, or between the electrodes and the current collectors is sufficient. And the opposing area of the negative electrode 42 and the positive electrode 44 through the separator 46 increases. Further, since the respective electrodes swell and increase in thickness, a compressive stress is applied to the intervening separator 46 to be compressed, so the distance between the negative electrode 42 and the positive electrode 44 is reduced. The resistance value between the electrodes is suppressed.
Therefore, an increase in internal resistance can be prevented, a large current can be obtained, charge / discharge efficiency can be improved, and the electric double layer capacitor 1 which is an electrochemical cell excellent in electrical characteristics can be provided.

"Production method"
Next, a method for producing an electric double layer capacitor (nonaqueous electrolyte battery) which is an electrochemical cell of the present invention will be described.
The manufacturing method described in the present embodiment is a method for manufacturing the electric double layer capacitor 1 having the above configuration. First, the intermediate layer 26, the protective layer 27, the external terminal 60, the first metal layer 62, the external terminal 70, and the The container body 20 provided with the second metal layer 72 is prepared.
Next, the seal ring 30 is joined to the peripheral edge of the opening of the container body 20, that is, the upper end surface 23 of the side wall 24 by the brazing material 32.
Next, nickel plating is performed so as to cover the seal ring 30, the brazing material 32, and the upper end surface 23. Examples of the nickel plating include electrolytic nickel plating and electroless nickel plating.

  Next, the positive electrode current collector 45 is welded or adhered to the inner bottom surface of the container body 20 with a conductive adhesive or the like, and then the positive electrode side electrode 44 is adhered thereon with a conductive paste (a paste layer made of a carbon-containing material). Further, after placing the separator 46 on the positive electrode 44, an arbitrary amount of the electrolytic solution 50 is injected into the container body 20. The injection amount of the electrolytic solution 50 at this time can be determined in consideration of the type of non-aqueous solvent, element characteristics, the porosity of the electric double layer capacitor 1, and the like.

  Here, for example, when a glass fiber laminate is used as the separator 46, the separator 46 may be heated in advance before injecting the electrolytic solution 50 as necessary. Thus, by heating the separator 46, the adsorbed water and various organic substances on the surface of the glass fiber laminate can be removed by oxidation or volatilization. Can be impregnated.

  Next, after the negative electrode current collector 43 is welded to one surface of the lid 10 or bonded with a conductive adhesive or the like, the negative electrode side electrode 42 is bonded thereon with the same conductive paste as described above. The lid 10 is placed on the seal ring 30 so that the side electrode 42 contacts the separator 46. Alternatively, the negative electrode side electrode 42 is placed so as to contact the separator 46, the lid body 10 provided with the negative electrode current collector 43 in advance is placed on the seal ring 30, and the negative electrode current collector 43 and the negative electrode side electrode are placed. 42 is bonded.

  Here, the positive electrode side electrode 44 and the negative electrode side electrode 42 absorb the electrolytic solution 50 and expand. The pair of expanded electrodes 44 and 42 applies a compressive load to both surfaces of the separator 46. Thereby, the part pinched | interposed between the electrodes of the separator 46 may be compressed and thickness may reduce.

  Next, the lid 10 and the seal ring 30 are welded while being partially melted to form an unsealed body. As a method of partial welding of the lid 10 and the seal ring 30 at this time, for example, nickel plating of the lid 10 and nickel covering the seal ring 30 using resistance welding, laser welding, thermal welding or the like. The method of welding partially with plating is mentioned, Especially resistance welding is suitable. Note that the above-mentioned “partial welding” means that the lid body 10 and the seal ring 30 are welded by spot welding or the like in which the welding portions are separated from each other.

Next, in the present embodiment, impurities such as moisture are removed by heating the non-sealed body in which the lid 10 and the seal ring 30 are partially welded at 200 ° C. or higher and lower than 900 ° C. as necessary. It can be removed from the electrolytic solution 50 or a part of the non-aqueous solvent can be evaporated to increase the concentration of the supporting salt in the electrolytic solution 50. In addition, by performing the preliminary heating described above, the viscosity of the electrolytic solution 50 can be reduced and the polarizable electrode 40 (the negative electrode 42 and the positive electrode 44) or the separator 46 can be sufficiently impregnated with the electrolytic solution 50. .
The heating method in this case is not particularly limited, and examples thereof include a method by energizing the lid 10, a laser irradiation method, and a heating method by warm air. Among these, a method of energizing the lid 10 is preferable. Thus, by energizing the lid 10, the temperature of the electrolytic solution 50 rises in a short time, and the impurities in the electrolytic solution 50 can be efficiently removed. Moreover, since the energization to the lid body 10 can also serve as partial welding of the lid body 10 and the seal ring 30 described above, the manufacturing efficiency of the electric double layer capacitor 1 can be improved.
The heating time can be determined in consideration of the type of non-aqueous solvent, the heating method, and the like, and is preferably 1 msec or more, for example. At this time, when the electrolytic solution 50 contains cyclic carbonate or cyclic sulfone having a relatively high boiling point, the electrolytic solution 50 does not easily volatilize, and an appropriate amount of the electrolytic solution 50 remains in the storage container 2. To do. In addition, by performing preliminary heating to remove low-boiling impurities, the low-boiling impurities are vaporized when the sealing process described later or flow soldering is performed, and the electric double layer capacitor 1 Can be prevented from being damaged.

Next, the inside of the storage container 2 is sealed by the lid body 10 and the container main body 20 by welding the lid body 10 and the seal ring 30 which are in a non-sealed body state. At this time, the method for welding the lid 10 and the seal ring 30 is not particularly limited, and examples thereof include seam welding by resistance welding. By performing this seam welding, the nickel plating of the lid 10 and the nickel plating covering the seal ring 30 are welded. In such welding, the electrolytic solution 50 is exposed to the melting point (800 to 1455 ° C.) of nickel plating. However, when the composition contains a cyclic carbonate or a chain sulfone having a relatively high boiling point, the electrolytic solution 50 can be easily electrolyzed. An appropriate amount of the electrolytic solution 50 remains in the storage container 2 without the liquid 50 volatilizing. In addition, since the entire amount of the electrolytic solution 50 does not volatilize easily, the storage container 2 can be prevented from being damaged during welding.
The electric double layer capacitor 1 of this embodiment is obtained by the procedure as described above.

  Here, in the present embodiment, a sufficient amount of the electrolytic solution 50 is impregnated in the void portions of the negative electrode current collector 43 and the positive electrode current collector 45 made of a high porosity material. Thereby, even when the electrolyte solution 50 impregnated in the negative electrode side electrode 42 or the positive electrode side electrode 44 is volatilized by welding heat when the storage container 2 is sealed by welding, each negative electrode current collector 43 or positive electrode The electrolytic solution 50 impregnated in the current collector 45 is gradually discharged and supplied to each electrode. Then, the electrolyte solution 50 supplied from each current collector impregnates the negative electrode side electrode 42 and the positive electrode side electrode 44, and each electrode is sufficiently swollen to increase the thickness. Even if it is large, between electrode-separator and between electrode-current collectors will be in the state where it adhered enough, and it can control that contact resistance between each member increases. Therefore, an increase in internal resistance is prevented, a large current is obtained, charge / discharge efficiency is improved, and the electric double layer capacitor 1 having excellent electrical characteristics can be manufactured.

  Next, an Example and a comparative example are shown and this invention is demonstrated further more concretely. The scope of the present invention is not limited by this example, and the electrochemical cell and the method for producing the same according to the present invention can be implemented with appropriate modifications without departing from the scope of the present invention. It is.

[Example 1]
In Example 1, first, an electric double layer capacitor having a rectangular shape in plan view as shown in FIG. 1 was produced as an electrochemical cell. In the present embodiment, the negative electrode current collector 43 shown in FIG. 1 is not provided, and the negative electrode 42 is directly attached to the lid body 10, except that the electric double layer capacitor 1 shown in FIG. A cell was prepared.

  First, a commercially available activated carbon electrode (thickness = 0.23 mm) was prepared, and this was cut into 1.7 mm × 1.0 mm as a positive electrode side electrode 44 and a negative electrode side electrode 42.

Next, the negative electrode side electrode 42 was bonded to the lid 10 obtained by electrolytic nickel plating on a Kovar flat plate with a conductive paste (commercially available phenol-based conductive paste).
Next, a Kovar seal ring 30 is joined to the periphery of the opening of the container body 2 having the bottom wall portion 21 made of the ceramic base material 22 and the intermediate layer 26 and the ceramic side wall portion 24 by silver brazing. did.
Next, a positive electrode current collector 45 made of a high porosity material (aluminum foam metal material: 1 × 1.7 mm, thickness = 180 μm) was joined to the inner bottom surface of the container body 20 by resistance welding.
Next, the positive electrode 44 was bonded to the positive electrode current collector with the same conductive paste as described above, and the separator 46 (a glass fiber laminate processed to 2.3 mm × 1.6 mm) was placed on the positive electrode 44. .
Next, a commercially available electrolytic solution (PC + EC + DMC / 1.5M, SBP-BF ₄ , specific gravity: 1.26) is injected in an amount of 1.6 μL from the positive electrode 44 into the container body 20 as the electrolytic solution 50. The lid 10 was placed on the seal ring 30 so that the negative electrode 42 was in contact with the separator 46.
Next, the lid 10 and the seal ring 30 were partially welded by spot welding to form an unsealed body, and then the lid 10 was heated at 250 ° C. for 30 minutes in an N ₂ atmosphere.
Subsequently, the storage container 2 was sealed by seam welding by resistance welding, and the electric double layer capacitor 1 was obtained.

  Then, regarding the electric double layer capacitors of Experimental Examples 1 to 8 manufactured under the above conditions, heat treatment equivalent to reflow soldering was performed, and each resistance value was measured after initial value, initial heat treatment, and 5 times after reflow. Is shown in Table 1 below. The resistance value was measured using an LCR meter KC-594B type manufactured by KDK and measured at an alternating current of 1 KHz using the R function.

  As the results shown in Table 1, the electric double layer capacitors of Experimental Examples 1 to 8 in which the current collector defined in the claims of the present invention is connected to the positive electrode are the initial values of the internal resistance after fabrication. Are all suppressed to 22.8Ω or less (average: 20.43Ω). That is, in Experimental Examples 1 to 8, the dimensional accuracy error of each electrode, each current collector, and each member of the separator is accumulated, and a large error is generated such that sufficient adhesion between the electrode and the separator cannot be obtained. In addition, even when the electrolyte impregnated in the electrode or separator is volatilized by welding heat when sealing the storage container, the electrolyte discharged from each current collector impregnates each electrode and swells. Thus, it is considered that the gaps between the respective members are filled and the internal resistance is suppressed from increasing.

  Furthermore, in Experimental Examples 1 to 8, the resistance increase rates were all 1 times or less (average: 0.9 times) even after heat treatment equivalent to reflow soldering that was continuously exposed to a high temperature environment. . That is, in Experimental Examples 1 to 8, according to the above experimental results, even if the electrolytic solution impregnated in the electrode or separator is volatilized by repetition of charge and discharge, the electrolytic solution discharged from each current collector is By impregnating and swelling each electrode, it is considered that the gap between the respective members is filled, and the increase in internal resistance is suppressed without separating each current collector from each electrode.

According to the electrochemical cell of the present invention, by providing a pair of current collectors made of a high porosity material, the current collector is impregnated even when the electrolyte impregnated in the electrode or separator is volatilized. By supplying the electrolyte to the electrode or separator, the electrode and the separator, or the electrode and the current collector are in close contact with each other, and an increase in internal resistance is prevented to obtain a large current. It is done. As a result, productivity and yield are high, and in addition, electrical double layer capacitors mounted on energy harvesting equipment, etc. have large temperature changes and humidity changes, and excellent electrical characteristics in fields that require harsh environmental resistance. An electrochemical cell can be provided.

1 ... Electric double layer capacitor (non-aqueous electrolyte battery: electrochemical cell),
2. Storage container,
10 ... lid,
20 ... the container body,
15 ... electrochemical element,
40: Polarizable electrodes (a pair of electrodes),
42 ... negative electrode (a pair of electrodes),
44 ... Positive electrode (a pair of electrodes),
46 ... separator,
43 ... negative electrode current collector (a pair of current collectors),
45 ... positive electrode current collector (a pair of current collectors),
50 ... Electrolyte 60, 70 ... External terminal

Claims (12)

A chip-type electrochemical cell equipped with an electrochemical element inside a storage container in which a lid and a container main body are sealed, and can be charged / discharged via an external terminal,
The electrochemical element is bonded to the storage container so as to be respectively disposed outside the pair of electrodes, a pair of electrodes disposed opposite to each other, a separator disposed between the pair of electrodes, A pair of current collectors that are electrically connected by being adjacent to the pair of electrodes, and an electrolytic solution that is housed in the storage container and impregnated in the pair of electrodes and the separator,
One or both of the pair of current collectors are made of a high porosity material having voids, and the voids are impregnated with the electrolytic solution.   2. The electrochemical cell according to claim 1, wherein the high porosity material forming the pair of current collectors has a porosity of 60 to 98%.   The electrochemical cell according to claim 1 or 2, wherein the high void material forming the pair of current collectors is a foam metal body.   4. The electrochemical cell according to claim 3, wherein the foam metal body is a foam metal material of aluminum or stainless steel.   The electrochemical cell according to claim 1 or 2, wherein the high void material forming the pair of current collectors is a metal wire net.   The electrochemical cell according to claim 5, wherein the metal wire mesh is made of aluminum or stainless steel.   7. The electrochemical according to claim 3, wherein the pair of current collectors made of the metal foam body or the metal wire net is covered with a carbon material. cell.   The electrochemical cell according to claim 1 or 2, wherein the high void material forming the pair of current collectors is carbon paper.   The electrochemical cell according to any one of claims 1 to 7, wherein the storage container and the pair of current collectors are welded.   The electrochemical cell according to any one of claims 1 to 8, wherein the storage container and the pair of current collectors are fixed with a conductive adhesive.   The electrolytic solution impregnated in the pair of current collectors flows into the pair of electrodes, and the pair of electrodes is swollen by the impregnation of the electrolytic solution, whereby a compressive load is applied to the separator. The electrochemical cell according to any one of claims 1 to 10, wherein the electrochemical cell is characterized.   The paste layer made of a carbon-containing material and having a through-hole is provided between each of the pair of current collectors and the pair of electrodes. The electrochemical cell according to any one of the above.

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