JP2004253562A - Electrochemical capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrochemical capacitor which has such a structure as to be easily reduced in size and weight, and which can surely acquire superior charge/discharge properties even if a case using a flexible film is used. <P>SOLUTION: The electrochemical capacitor 1 mainly comprises an anode 10 (first electrode) and a cathode 20 (second electrode) which are opposite to each other, a separator 40 located between the anode 10 and the cathode 20 adjacently to these two electrodes, an electrolytic solution 30, and the case 50 which airtightly houses all these elements. The electrochemical capacitor 1 should satisfy a formula 1.0≤äA/(X+Y+Z)}≤1.4, where A is the volume of the electrolytic solution 30 filled in the case 50 at 25°C and 1 atm, X is a void volume in the anode 10, Y is a void volume in the cathode 20, and Z is a void volume in the separator 40. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【００９８】
本測定結果から実施例１、実施例２の結果は、各比較例に比し優れたレート特性を示すことが確認された。
【００９９】
また、実施例１及び実施例２並びに比較例１〜比較例４の各電気化学キャパシタのＸ及びＹの値は、エタノール含浸法により求めた。更に、実施例１及び実施例２並びに比較例１〜比較例４の各電気化学キャパシタの各セパレータにはＺの値が既知のものを用いた。
【０１００】
【発明の効果】
以上説明したように、本発明によれば、小型化及び軽量化が容易な構成を有し、可とう性を有するフィルム（例えば、複合包装フィルム）を用いて形成したケースを使用する場合であっても、優れた充放電特性を確実に得ることのできる電気化学キャパシタを提供することができる。特に、本発明によれば、厚さの薄いフィルム状の電気化学キャパシタ（例えば、厚さが３００〜５００μｍの電気化学キャパシタ）を提供することができる。
【図面の簡単な説明】
【図１】本発明の電気化学キャパシタの好適な一実施形態を示す正面図である。
【図２】図１に示す電気化学キャパシタの内部をアノード１０の表面の法線方向からみた場合の展開図である。
【図３】図１に示す電気化学キャパシタを図１のＸ１−Ｘ１線に沿って切断した場合の模式断面図である。
【図４】図１に示す電気化学キャパシタを図１のＸ２−Ｘ２線に沿って切断した場合の要部を示す模式断面図である。
【図５】図１に示す電気化学キャパシタを図１のＹ−Ｙ線に沿って切断した場合の要部を示す模式断面図である。
【図６】図１に示す電気化学キャパシタのケースの構成材料となるフィルムの基本構成の一例を示す模式断面図である。
【図７】図１に示す電気化学キャパシタのケースの構成材料となるフィルムの基本構成の別の一例を示す模式断面図である。
【図８】図１に示す電気化学キャパシタのアノードの基本構成の一例を示す模式断面図である。
【図９】図１に示す電気化学キャパシタのカソードの基本構成の一例を示す模式断面図である。
【符号の説明】
１…電気化学キャパシタ、１０…アノード、１２…アノード用リード線、１４…絶縁体、２０…カソード、２２…カソード用リード線、２４…絶縁体、３０…電解質溶液、４０…セパレータ、５０…ケース、６０…素体。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an electrochemical capacitor.
[0002]
[Prior art]
Electrochemical capacitors such as an electric double layer capacitor utilize capacitance caused by an electric double layer generated at an interface between an electrode electrolyte solution of a polarizable electrode. The polarizable electrode is generally formed using a porous carbon material as a constituent material. The capacitance of the double layer interface formed on the electrode of the electrochemical capacitor is characterized by being larger than other capacitors, and is usually 1 mF or more.
[0003]
Electrochemical capacitors such as electric double-layer capacitors can be easily reduced in size and weight. For example, they can be used as backup power supplies for portable equipment (small electronic equipment) and auxiliary power supplies for hybrid vehicles. It is expected, and various studies are being made to improve its performance.
[0004]
As one of the above studies, based on the void capacity of a porous polarizable electrode and a porous separator formed mainly of a carbon material (powder activated carbon, granular activated carbon or activated carbon fiber), these are accommodated. A suitable range (1.1 to 1.6 times the void volume) of the electrolyte solution to be filled in the outer container (for example, a stainless steel can) is determined. An electric double layer capacitor (electric double layer capacitor) configured to fall within the range has been proposed (for example, see Patent Document 1 (Example 1) below). The “void volume” is a value represented by (X + Y + Z) described later in this specification.
[0005]
[Patent Document 1]
Japanese Patent No. 308399
[0006]
[Problems to be solved by the invention]
However, in order to further reduce the size and weight of the electric double-layer capacitor, instead of an outer container (metal container) described in Patent Literature 1 described above, which has no flexibility, it is lightweight. The present inventors have found that there is the following problem when using a case formed using a flexible film (for example, a composite packaging film) that can be easily thinned.
[0007]
That is, when using a case formed using a flexible film, even if the volume of the electrolyte solution filled in the case is adjusted to the range described in Patent Document 1, sufficient charge / discharge characteristics are ensured. In some cases, they could not be obtained, and furthermore, they could not be discharged. In particular, when a range exceeding 1.4 out of the above range is intended to fill the electrolyte solution as much as possible in order to secure a sufficient electric double layer interface, the charge / discharge characteristics are poor. On the contrary, there was a problem of lowering.
[0008]
Further, the above-described problem in the electric double layer capacitor has similarly occurred in other electrochemical capacitors such as a pseudo capacitance capacitor having a similar configuration.
[0009]
The present invention has been made in view of the above-mentioned problems of the related art, and has a configuration in which a size and a weight can be easily reduced, and a case where a case formed using a flexible film is used. It is another object of the present invention to provide an electrochemical capacitor capable of reliably obtaining excellent charge / discharge characteristics.
[0010]
[Means for Solving the Problems]
The present inventors have intensively studied to achieve the above object, and as a result, in the case of an electrochemical capacitor having a case formed using a flexible film, it is effective to have a configuration satisfying the following conditions. And arrived at the present invention.
[0011]
That is, the present invention provides a flat plate-shaped first electrode and a flat plate-shaped second electrode facing each other, and a flat plate-shaped separator disposed adjacent to between the first electrode and the second electrode. , An electrolyte solution, a first electrode, a second electrode, a separator and a case formed from a film accommodating the electrolyte solution in a sealed state, and the first electrode and the second electrode are Each contains an electron conductive porous body as a constituent material, the separator is made of an insulating porous body, and at least a part of the electrolyte solution is contained inside the first electrode and the second electrode, and inside the separator. The volume A of the electrolyte solution filled in the case at 25 ° C. and 1 atm, the void volume X in the first electrode, the void volume Y in the second electrode, and the void volume Z in the separator Is represented by the following equation (1). Which satisfies the following conditions:
1.0 ≦ {A / (X + Y + Z)} ≦ 1.4 (1)
[0012]
Here, in the electrochemical capacitor of the present invention, the plate-shaped separator disposed between the plate-shaped first electrode and the plate-shaped second electrode has one surface thereof connected to the first electrode of the first electrode. 2 is disposed in contact with a surface on the electrode side (hereinafter, referred to as “inner surface”), and the other surface is a surface of the second electrode on the first electrode side (hereinafter, referred to as “inner surface”). Are arranged in contact with That is, in the electrochemical capacitor of the present invention, the separator is arranged in a state of being in contact with the first electrode and the second electrode, but is not joined by thermocompression bonding or the like.
[0013]
When the separator is bonded to the first electrode and the second electrode by thermocompression bonding or the like, 1) pores or voids contributing to the formation of the electric double layer in both electrodes are crushed. 2) The electric double layer in the separator. Since the pores contributing to the formation are partially crushed, the internal resistance increases. In particular, in a small electrochemical capacitor having a small capacitance and mounted on a small electronic device, a slight difference in internal resistance (impedance) significantly affects discharge characteristics. When the internal resistance increases, the ohmic loss (IR loss) increases and the discharge characteristics deteriorate. In particular, when a large current is discharged, the ohmic loss increases, and the discharge may not be possible. Therefore, the electric double layer capacitor of the present invention employs a configuration in which the separator is disposed in a state of being in contact with the first electrode and the second electrode as described above.
[0014]
Further, as described above, when the configuration in which the separator is disposed in contact with the first electrode and the second electrode is adopted, the contact state between the separator and the first electrode, and the separator and the second It is necessary to adjust the contact state with the electrodes so that the contact resistance becomes the minimum value. If the state of contact between the separator and the first electrode and the state of contact between the separator and the second electrode are insufficient, the internal resistance of the electric double layer capacitor increases and the discharge characteristics deteriorate.
[0015]
However, when a case formed by using a flexible composite packaging film, such as the electric double layer capacitor of the present invention, is employed, a predetermined structure is formed on the laminate including the first electrode, the separator, and the second electrode. Even if pressure is applied, the contact state between the separator and the first electrode at the time of manufacture, and the contact state between the separator and the second electrode are adjusted such that the contact resistance becomes the minimum value, the case is not considered. When the volume of the electrolyte solution filled in the inside becomes larger than a predetermined amount, the case formed of the flexible film during subsequent use (or storage) is deformed by the internal pressure, and the separator and the first The present inventors have found that the state of contact with the electrode and the state of contact between the separator and the second electrode are poor. When the case is deformed by the internal pressure and the above-mentioned contact state becomes poor, a liquid film of an electrolyte solution is formed between the separator and the first electrode and between the separator and the second electrode, and the internal resistance is reduced. Is thought to increase.
[0016]
Furthermore, the contact state between the separator and the first electrode, and the contact state between the separator and the second electrode are kept good, and the increase in the internal resistance due to the above-mentioned poor contact hardly occurs. Even so, the shape of the case formed from the flexible film is deformed during manufacturing and during use (or storage) thereafter, so that the first electrode, the separator, and the first The electrolyte solution moves between a region occupied by the laminate composed of the two electrodes (hereinafter, referred to as a “primary body” as necessary) and a region other than the region occupied by the laminate, and the inside of the primary body Varies between the time of manufacture and during use (or storage) thereafter.
[0017]
That is, in the electrochemical capacitor including the case formed of the flexible film, the region where the electric double layer can be formed in the element body changes during manufacturing and during use (or storage) thereafter. . Therefore, in order to obtain the highest possible charge / discharge characteristics, the volume of the electrolyte solution to be filled in the case must be determined in consideration of the change in the amount of the electrolyte solution held inside the element body. The present inventors have found.
[0018]
The present inventors have determined that the volume range (particularly the maximum value) of the electrolyte solution that can be filled in the case is as flexible as the outer container (metal container) described in Patent Document 1 described above. It has been found that the range is difficult to predict {the range represented by the above (1)} from the numerical range employed in the electrochemical capacitor of the type using no container.
[0019]
On the other hand, an electrochemical capacitor of a type using a container having no flexibility such as the outer container (metal container) described in Patent Document 1 described above (for example, a button-type electric double-layer capacitor) Since there is no deformation (deformation due to flexibility) of the container, the contact state between the separator and the first electrode, and the contact state between the separator and the second electrode, which are set at the time of manufacture, are determined during the subsequent use. (Or during storage). Therefore, it is not necessary to adopt the configuration conditions specific to the electric double layer capacitor of the present invention.
[0020]
Also, in the case of a so-called wound electric double layer capacitor (a type in which a laminate having at least a structure in which a first electrode, a separator, and a second electrode are sequentially laminated in this order) is manufactured. During the winding operation, an optimal pressure is applied to the first electrode, the laminated body including the separator and the second electrode, and the contact state between the separator and the first electrode, which is set at the time of manufacture, and the separator and the second electrode. The state of contact with the second electrode is maintained during subsequent use (or storage). Therefore, it is not necessary to adopt the configuration conditions specific to the electric double layer capacitor of the present invention.
[0021]
Here, in the present invention, when the electrolyte solution is filled in the case in a range where the value of {A / (X + Y + Z)} exceeds 1.4, the internal resistance of the electric double layer capacitor (particularly, the internal resistance at the interface between the electrode and the separator) And sufficient charge / discharge characteristics cannot be obtained. When the electrolyte solution is filled in the case where the value of {A / (X + Y + Z)} is less than 1.0, the electrolyte solution does not sufficiently spread in the pores of each electrode, and the size of the electrolyte solution is not sufficient. The electric double layer interface cannot be formed, and the electric conductivity of the electrode decreases. As a result, the internal resistance increases, and sufficient charge / discharge characteristics cannot be obtained. From the above viewpoints, in the present invention, the value of {A / (X + Y + Z)} is 1.0 to 1.4, preferably 1.05 to 1.35.
[0022]
Therefore, the electrochemical capacitor of the present invention that satisfies the above-described configuration conditions has a configuration that is easy to reduce in size and weight, and uses a case formed using a flexible film (for example, a composite packaging film). Even in such a case, excellent charge / discharge characteristics can be reliably obtained. In particular, according to the present invention, it is possible to provide a thin film-shaped electrochemical capacitor (for example, an electrochemical capacitor having a thickness of 300 to 500 μm).
[0023]
Further, the electrochemical capacitor of the present invention includes a case formed using a flexible film that is lightweight and easily thinned, so that the shape of the electrochemical capacitor itself may be a thin film. it can. Therefore, the original volume energy density can be easily improved, and the energy density per unit volume of the installation space where the electrochemical capacitor is to be installed (hereinafter referred to as “volume based on the volume of the space to be installed”). Energy density ”) can be easily improved.
[0024]
The “volume energy density” of an electrochemical capacitor is originally defined as the ratio of the total output energy to the total volume including the container of the electrochemical capacitor. On the other hand, "volume energy density based on the volume of the space to be installed" refers to the electrochemical capacitor with respect to the apparent volume calculated based on the maximum length, maximum width, and maximum thickness of the electrochemical capacitor. Means the ratio of the total output energy. In fact, when an electrochemical capacitor is mounted on a small electronic device, it is necessary to improve the volume energy density based on the volume of the space to be installed together with the improvement of the original volume energy density described above. This is important from the viewpoint of effectively utilizing the limited space in a state where the dead space is sufficiently reduced.
[0025]
Here, in the present invention, “film” refers to a film having flexibility. Further, “void volume X” and “void volume Y” are values indicating the total pore volume in each electrode. In the electrode, a void formed between particles that are a constituent material of the electrode or If there are minute cracks in the constituent material of the electrode, the value is a value calculated by adding the volume of the voids and the volume of the cracks. Further, “void volume Z” refers to the total pore volume in the separator, but in the separator, there are voids formed between particles that are the constituent material of the separator or fine cracks in the constituent material of the separator. In this case, the value is a value calculated by adding the volume and crack of the void.
[0026]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, preferred embodiments of the case where the electrochemical capacitor according to the present invention is applied to an electric double layer capacitor will be described in detail with reference to the drawings. In the following description, the same or corresponding parts will be denoted by the same reference characters, without redundant description.
[0027]
FIG. 1 is a front view showing a preferred embodiment of the electrochemical capacitor of the present invention. FIG. 2 is a developed view when the inside of the electrochemical capacitor shown in FIG. 1 is viewed from the normal direction of the surface of the anode 10. FIG. 3 is a schematic cross-sectional view when the electrochemical capacitor shown in FIG. 1 is cut along the line X1-X1 in FIG. FIG. 4 is a schematic cross-sectional view showing a main part when the electrochemical capacitor shown in FIG. 1 is cut along the line X2-X2 in FIG.
[0028]
As shown in FIGS. 1 to 5, the electric double-layer capacitor 1 mainly includes a flat anode 10 (first electrode) and a flat cathode 20 (second electrode) facing each other, One end is electrically connected to the flat separator 40 disposed adjacent to the cathode 20, the electrolyte solution 30, the case 50 for accommodating them in a sealed state, and the anode 10. And an anode lead 12 whose other end protrudes outside the case 50, and a cathode lead whose one end is electrically connected to the cathode 20 and whose other end protrudes outside the case 50. And a lead 22. Here, the “anode” 10 and the “cathode” 20 are determined based on the polarity at the time of discharging of the electrochemical capacitor 1 for convenience of explanation.
[0029]
The electrochemical capacitor 1 has a configuration described below in order to achieve the above-described object of the present invention.
[0030]
Hereinafter, details of each component of the present embodiment will be described with reference to FIGS.
[0031]
As described above, the case 50 has the first film 51 and the second film 52 facing each other. Here, as shown in FIG. 2, the first film 51 and the second film 52 in the present embodiment are connected. That is, the case 50 in the present embodiment bends a rectangular film made of a single composite packaging film at a folding line X3-X3 shown in FIG. 2, and sets a pair of opposing edges of the rectangular film ( The edge 51B of the first film 51 and the edge 52B) of the second film in the figure are overlapped and formed by using an adhesive or performing heat sealing.
[0032]
The first film 51 and the second film 52 indicate portions of the film having surfaces (F51 and F52) facing each other when a single rectangular film is bent as described above. . Here, in this specification, the respective edges of the first film 51 and the second film 52 after being joined are referred to as “seal portions”.
[0033]
This eliminates the need to provide a seal portion for joining the first film 51 and the second film 52 at the portion of the fold line X3-X3, so that the seal portion in the case 50 can be further reduced. As a result, the volume energy density based on the volume of the space where the electrochemical capacitor 1 is to be installed can be further improved.
[0034]
In the case of the present embodiment, as shown in FIGS. 1 and 2, one end of each of the anode lead 12 and the cathode lead 22 connected to the anode 10 is connected to the edge 51 </ b> B of the first film 51 described above. The edge 52B of the second film is disposed so as to protrude outside from a seal portion joined to the seal portion.
[0035]
As described above, the films constituting the first film 51 and the second film 52 are films having flexibility. Since the film is lightweight and easily thinned, the shape of the electrochemical capacitor itself can be made thin. Therefore, the original volume energy density can be easily improved, and the volume energy density based on the volume of the space where the electrochemical capacitor is to be installed can be easily improved.
[0036]
This film is not particularly limited as long as it is a flexible film.However, while ensuring sufficient mechanical strength and lightness of the case, moisture and air can enter the inside of the case from the outside and enter the outside of the case from the inside of the case. From the viewpoint of effectively preventing the escape of the electrolyte component into the composite package, the composite package has at least an innermost layer made of a synthetic resin in contact with the electrolyte solution and a metal layer disposed above the innermost layer. Preferably, it is a "film."
[0037]
As a composite packaging film that can be used as the first film 51 and the second film 52, for example, a composite packaging film having a configuration shown in FIGS. The composite packaging film 53 shown in FIG. 6 includes a synthetic resin innermost layer 50a that comes into contact with the electrolyte solution on the inner surface F50a and a metal disposed on the other surface (outer surface) of the innermost layer 50a. And a layer 50c. The composite packaging film 54 shown in FIG. 7 has a configuration in which an outermost layer 50b made of a synthetic resin is further disposed on the outer surface of the metal layer 50c of the composite packaging film 53 shown in FIG.
[0038]
The composite packaging film that can be used as the first film 51 and the second film 52 includes one or more synthetic resin layers including the innermost layer described above, and two or more layers including a metal layer such as a metal foil. Although it is not particularly limited as long as it is a composite packaging material having a layer, from the viewpoint of more reliably obtaining the same effect as described above, the innermost layer and the innermost layer, such as the composite packaging film 54 shown in FIG. Three layers having an outermost layer made of a synthetic resin disposed on the outer surface side of the case 50 farthest from the outermost layer and at least one metal layer disposed between the innermost layer and the outermost layer More preferably, it is composed of the above layers.
[0039]
The innermost layer is a layer having flexibility, and its constituent material is capable of expressing the above-mentioned flexibility, and has a chemical stability (chemical reaction, dissolution, It is not particularly limited as long as it is a synthetic resin having the property of not causing swelling) and chemical stability against oxygen and water (moisture in air), and furthermore, oxygen, water (moisture in air) and electrolyte Materials having a property of low permeability to the components of the solution are preferred. For example, engineering plastics, and thermoplastic resins such as polyethylene, polypropylene, modified polyethylene acid, modified polypropylene acid, polyethylene ionomer, and polypropylene ionomer are exemplified.
[0040]
In addition, "engineering plastics" refers to plastics having excellent mechanical properties, heat resistance, and durability as used in mechanical parts, electric parts, housing materials, and the like.For example, polyacetal, polyamide, polycarbonate, Polyoxytetramethyleneoxy terephthaloyl (eg, polybutylene terephthalate, polyethylene terephthalate, polyimide, polyphenylene sulfide, etc.).
[0041]
When a layer made of a synthetic resin such as the outermost layer 50b is provided in addition to the innermost layer 50a as in the composite packaging film 54 shown in FIG. Also, the same constituent material as the innermost layer may be used. Further, as the layer made of the synthetic resin, for example, a layer made of an engineering plastic such as polyethylene terephthalate (PET) or polyamide (nylon) may be used.
[0042]
The method of sealing all the seal portions in the case 50 is not particularly limited, but is preferably a heat seal method from the viewpoint of productivity.
[0043]
The metal layer is preferably a layer formed of a metal material having corrosion resistance to oxygen, water (moisture in air) and an electrolyte solution. For example, a metal foil made of aluminum, an aluminum alloy, titanium, chromium, or the like may be used.
[0044]
Next, the anode 10 and the cathode 20 will be described. FIG. 8 is a schematic cross-sectional view showing an example of the basic configuration of the anode of the electrochemical capacitor shown in FIG. FIG. 9 is a schematic cross-sectional view showing an example of the basic configuration of the cathode of the electrochemical capacitor shown in FIG.
[0045]
As shown in FIG. 8, the anode 10 includes a current collector 16 and a porous layer 18 formed on the current collector 16 and formed of an electron conductive porous body. As shown in FIG. 9, the cathode 20 includes a current collector 26 and a porous layer 28 formed on the current collector 26 and made of an electron conductive porous material.
[0046]
The current collector 16 and the current collector 26 are not particularly limited as long as they are good conductors capable of sufficiently transferring electric charges to the porous layer 18 and the porous layer 28, and are used in known electric double layer capacitors. Current collectors can be used. For example, the current collector 16 and the current collector 26 include a metal foil such as aluminum.
[0047]
The constituent material of the porous layer 18 and the porous layer 28 is not particularly limited, and those used for the porous layer constituting the polarizable electrode such as a carbon electrode used in a known electric double layer capacitor. The same material as described above can be used. For example, it can be obtained by activating coking coal (for example, petroleum coke produced from delayed coker using bottom oil of fluid catalytic cracking unit of petroleum heavy oil or bottom oil of vacuum distillation unit as starting oil). A carbon material (for example, activated carbon) used as a main component of the constituent material can be used. Other conditions (the types and contents of constituent materials other than the carbon material such as the binder) are not particularly limited. For example, a conductive auxiliary (for example, carbon black) for imparting conductivity to carbon powder and a binder (for example, polytetrafluoroethylene, hereinafter, referred to as PTFE) may be added.
[0048]
However, from the viewpoint of ensuring a sufficient contact interface with the electrolyte solution, the void volume (void volume in the anode 10) X of the porous layer 18 is preferably 60 to 80 μL, and more preferably 65 to 75 μL. More preferred. Further, the void volume (void volume in the cathode 20) Y of the porous layer 28 is preferably from 60 to 80 μL, and more preferably from 65 to 75 μL. In addition, the void volume X and the void volume Y can be determined by an ethanol impregnation method.
[0049]
The separator 40 disposed between the anode 10 and the cathode 20 is not particularly limited as long as it is formed of an insulating porous material, and a separator used for a known electric double layer capacitor can be used. . For example, as the insulating porous body, a laminated body of a film made of polyethylene, polypropylene or polyolefin, a stretched film of a mixture of the above resins, or at least one constituent material selected from the group consisting of cellulose, polyester and polypropylene And a fiber non-woven fabric.
[0050]
However, from the viewpoint of ensuring a sufficient contact interface with the electrolyte solution, the void volume Z of the porous layer 18 is preferably 50 to 75 μL when the porous layer volume is 100 μL, and more preferably 60 to 70 μL. preferable. The method for determining the void volume Z is not particularly limited, and can be determined by a known method.
[0051]
The current collector 28 of the cathode 20 is electrically connected to one end of a cathode lead 22 made of, for example, aluminum, and the other end of the cathode lead 22 extends outside the case 50. On the other hand, the current collector 18 of the anode 10 is also electrically connected to one end of the anode lead conductor 12 made of, for example, copper or nickel, and the other end of the anode lead conductor 12 extends outside the encapsulation bag 14.
[0052]
The electrolyte solution 30 is filled in the inner space of the case 50, and a part of the electrolyte solution 30 is contained in the anode 10, the cathode 20, and the separator 40. The amount of the electrolyte solution 30 filled in the internal space of the case 50 is adjusted so as to satisfy the following conditions in order to obtain the above-described effects of the present invention.
[0053]
That is, the volume A [μL] of the electrolyte solution 30 filled in the case 50 at 25 ° C. and 1 atm, the void volume X [μL] in the anode 10, the void volume Y [μL] in the cathode 20, the separator The gap volume Z [μL] in 40 satisfies the condition represented by the following equation (1).
[0054]
1.0 ≦ {A / (X + Y + Z)} ≦ 1.4 (1)
[0055]
Thereby, even when a case formed using a flexible film (for example, a composite packaging film) is used, an electrochemical capacitor capable of reliably obtaining excellent charge / discharge characteristics can be configured. Can be.
[0056]
The electrolyte solution 30 is not particularly limited, and an electrolyte solution used for a known electric double layer capacitor (an aqueous electrolyte solution or an electrolyte solution using an organic solvent) can be used. However, since the electrolytic solution is electrochemically low in decomposition voltage, the withstand voltage of the capacitor is limited to a low level. Therefore, an electrolyte solution using an organic solvent (a non-aqueous electrolyte solution) is preferable.
[0057]
Further, the type of the electrolyte solution 30 is not particularly limited, but is generally selected in consideration of the solubility, dissociation degree, and viscosity of the solute, and has a high conductivity and a high potential window (high decomposition starting voltage). Desirably, it is an electrolyte solution. For example, as a typical example, a solution in which a quaternary ammonium salt such as tetraethylammonium tetrafluoroborate is dissolved in an organic solvent such as propylene carbonate, diethylene carbonate, or acetonitrile is used. In this case, it is necessary to strictly control the water content.
[0058]
Further, as shown in FIGS. 1 and 2, the portion of the anode lead 12 that contacts the sealing portion of the enclosing bag formed by the edge 51 </ b> B of the first film 51 and the edge 52 </ b> B of the second film includes And an insulator 14 for preventing contact between the anode lead 12 and a metal layer in a composite packaging film constituting each film. Further, the portion of the cathode lead 22 that contacts the sealing portion of the enclosing bag formed by the edge portion 51B of the first film 51 and the edge portion 52B of the second film is combined with the cathode lead 22 and a composite material forming each film. An insulator 24 for preventing contact with a metal layer in the packaging film is coated.
[0059]
Although the configuration of the insulator 14 and the insulator 24 is not particularly limited, for example, each of them may be formed of a synthetic resin. The insulator 14 and the insulator 24 may not be disposed as long as the contact of the metal layer in the composite packaging film with the anode lead 12 and the cathode lead 22 can be sufficiently prevented.
[0060]
Further, from the viewpoint that the electric double layer capacitor 1 can be installed in a limited narrow installation space in a portable small electronic device, the thickness of the electric double layer capacitor 1 (the thickness of the entire electric double layer capacitor 1) is 0.2. It is preferably from 2.0 to 2.0 mm, more preferably from 0.2 to 1.0 mm.
[0061]
Furthermore, from the viewpoint of being able to be installed even in a limited narrow installation space in a portable small electronic device, a laminated body including the anode 10, the separator 40, and the cathode 20 (from the first electrode, the separator and the second electrode). The thickness of the laminated body (thickness of the element body 60) is preferably 0.1 to 0.4 mm, and more preferably 0.1 to 0.3 mm.
[0062]
The electric double layer capacitor 1 has a capacitor capacity of 1 × 10 ^-3 To 1F, more preferably 0.01 to 0.10F. As a result, an electric double layer capacitor having a large capacity while having a film shape can be obtained. These can be used for IC cards, IC tags, etc., making use of their thin characteristics. In addition, applications for toys and the like and applications for portable devices will be expanded.
[0063]
Next, a method of manufacturing the case 50 and the electric double layer capacitor 1 described above will be described.
[0064]
The method of manufacturing the element body 60 (a stacked body in which the anode 10, the separator 40, and the cathode 20 are sequentially stacked in this order) is not particularly limited, and a known thin-film manufacturing technique employed in manufacturing a known electrochemical capacitor. Can be used.
[0065]
When the electrodes serving as the anode 10 and the cathode 20 are carbon electrodes, for example, a sheet-like electrode can be manufactured using a carbon material such as activated carbon that has been activated by a known method. In this case, for example, a carbon material is pulverized to about 5 to 100 μm to adjust the particle size, and then, for example, a conductive auxiliary (for example, carbon black) for imparting conductivity to the carbon powder and a binder (for example, polytetrafluoroethylene) are used. Fluoroethylene (hereinafter, referred to as PTFE)) is added and kneaded, and the kneaded material is drawn and formed into a sheet.
[0066]
Here, in addition to carbon black, powdered graphite or the like can be used as the conductive auxiliary agent, and as the binder, PVDF, PE, PP, fluororubber, or the like is used in addition to PTFE. be able to.
[0067]
In addition, in order to form a carbon electrode, it is necessary that fine particles obtained by pulverizing a carbon material and carbon black are evenly distributed and knotted with PTFE fiber with almost the same strength. It needs to be done vertically and horizontally.
[0068]
Next, the anode lead conductor 12 and the cathode lead 22 are electrically connected to the anode 10 and the cathode 20, respectively. The separator 40 is disposed in a state of contact (non-adhesion state) between the anode 10 and the cathode 20 to complete the element body 60.
[0069]
Next, an example of a method for manufacturing the case 50 will be described. First, when the first film and the second film are composed of the above-described composite packaging film, a dry lamination method, a wet lamination method, a hot melt lamination method, and an extrusion lamination method are used. And the like, using a known manufacturing method.
[0070]
For example, a film to be a synthetic resin layer constituting the composite packaging film, and a metal foil made of aluminum or the like are prepared. The metal foil can be prepared, for example, by rolling a metal material.
[0071]
Next, a composite packaging film (multilayer film) is formed by bonding a metal foil via an adhesive onto a film to be a layer made of a synthetic resin so as to preferably have the above-described configuration of a plurality of layers. Is prepared. Then, the composite packaging film is cut into a predetermined size, and one rectangular film is prepared.
[0072]
Next, as described above with reference to FIG. 2, one film is bent, and the sealing portion 51B (the edge portion 51B) of the first film 51 and the sealing portion 52B (the edge portion) of the second film 51 are bent. 52B) is heat-sealed by a desired sealing width under a predetermined heating condition using, for example, a sealing machine. At this time, in order to secure an opening for introducing the element body 60 into the case 50, a part where heat sealing is not performed is provided. Thus, the case 50 having the opening is obtained.
[0073]
Then, the element body 60 to which the anode lead conductor 12 and the cathode lead 22 are electrically connected is inserted into the case 50 having the opening. Then, the electrolyte solution 30 is injected. Subsequently, with a part of the anode lead 12 and a part of the cathode lead 22 inserted into the case 50, the opening of the case 50 is sealed using a sealing machine. Thus, the fabrication of the case 50 and the electric double layer capacitor 1 is completed.
[0074]
As described above, the preferred embodiments of the present invention have been described in detail, but the present invention is not limited to the above embodiments. For example, in the description of the above-described embodiment, a preferred configuration has been mainly described when the present invention is applied to an electric double-layer capacitor, but the electrochemical capacitor of the present invention is not limited to an electric double-layer capacitor. For example, a first plate-shaped electrode and a second plate-shaped electrode facing each other, such as a pseudo capacitor and a redox capacitor, are disposed adjacent to each other between the first electrode and the second electrode. The present invention is applicable to an electric double layer capacitor having a plate-shaped separator and an electrolyte solution and housed in a case formed of a flexible film.
[0075]
【Example】
Hereinafter, the contents of the electrochemical capacitor of the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.
[0076]
(Example 1)
According to the following procedure, an electrochemical capacitor having the same configuration as the electrochemical capacitor shown in FIG. 1 was manufactured.
[0077]
(1) Preparation of electrode
The anode (polarizable electrode) and the cathode (polarizable electrode) were prepared according to the following procedure. First, activated carbon material (specific surface area: 2000 m ² / G, manufactured by Kuraray Chemical Co., Ltd., trade name: “BP-20”), a binder {fluoro rubber, manufactured by DuPont, trade name: “Viton-GF”}, and a conductive auxiliary agent (acetylene black, Denki Kagaku Kogyo Co., Ltd.) Manufactured by DENKABLACK Co., Ltd.) in a mass ratio of carbon material: binder: conducting aid = 80: 10: 10, which is a solvent NMP (N-methylpyrrolidone). The solution was kneaded and kneaded to prepare a coating solution for electrode formation (hereinafter, referred to as “coating solution L1”).
[0078]
Next, this coating liquid L1 was uniformly applied on one surface of a current collector (thickness: 50 μm) made of aluminum foil. Thereafter, NMP was removed from the coating film by a drying treatment, and a laminate composed of the current collector and the dried coating film was pressed using a rolling roll to form a current collector made of aluminum foil (thickness: 50 μm). ) To form an electrode (hereinafter, referred to as “electrode E1”) having an electron-conductive porous layer (thickness: 37 μm) formed on one surface. Next, the electrode E1 is cut into a rectangular (size: 8 mm × 8 mm) shape, and further vacuum-dried at a temperature of 150 ° C. to 175 ° C. for 12 hours or more to obtain an electron conductive porous body. The anode and cathode mounted on the electrochemical capacitor of Example 1 were produced by removing the moisture adsorbed on the surface of the layer.
[0079]
(2) Production of electrochemical capacitor
First, a lead portion made of aluminum foil (width 2 mm, length 10 mm) is formed on the outer edge of the surface of the current collector on which the prepared electron-conductive porous layers (thickness: 37 μm) of the anode and the cathode are not formed. ). Next, the anode and the cathode are opposed to each other, and a separator (8.5 mm × 8.5 mm, thickness: 0.05 mm, manufactured by Nippon Kogyo Kogyo Co., Ltd., trade name: “TF4050”) is arranged between the anode and the cathode. Then, a laminated body (element body) was formed in which the anode, the separator, and the cathode were in contact with each other in this order (non-bonded state).
[0080]
Next, a sealant material was thermocompression-bonded to the tab portion. Next, the laminate (element) was placed in a case formed of a flexible composite packaging film, and the tab portions were heat-sealed. As a composite packaging film having flexibility, an innermost layer made of synthetic resin (layer made of modified polypropylene), a metal layer made of aluminum foil, and a layer made of polyamide are sequentially laminated in this order in contact with the electrolyte solution. Was used. Then, two composite packaging films were laminated and the edges thereof were heat-sealed.
[0081]
After an electrolyte solution (a 1.2 mol / L solution of triethylmethylammonium tetrafluoride in propylene carbonate) was injected into the case, vacuum sealing was performed to complete the manufacture of an electrochemical capacitor (electric double layer capacitor). At this time, the volume A [μL] of the electrolyte solution injected into the case was adjusted so that {A / (X + Y + Z)} = 1.30.
[0082]
(Comparative Example 1)
Except that the volume A [μL] of the electrolyte solution injected into the case was adjusted so that {A / (X + Y + Z)} = 1.43, the procedure and conditions were the same as those of the electrochemical capacitor of Example 1. An electrochemical capacitor was fabricated.
[0083]
(Comparative Example 2)
Except that the volume A [μL] of the electrolyte solution injected into the case was adjusted so that {A / (X + Y + Z)} = 0.95, the procedure and conditions were the same as those of the electrochemical capacitor of Example 1. An electrochemical capacitor was fabricated.
[0084]
(Example 2)
One side of the current collector made of aluminum foil in the same procedure and under the same conditions as in Example 1 except that the thickness of the electron conductive porous layer formed on one side of the current collector was 120 μm. An electrode having an electron conductive porous layer (thickness: 120 μm) formed thereon (hereinafter, referred to as “electrode E2”) was produced.
[0085]
Next, an anode and a cathode mounted on the electrochemical capacitor of Example 2 were manufactured in the same procedure and under the same conditions as in Example 1, except that the electrode E2 was cut so as to have a rectangular shape (size: 16 mm × 18 mm). Was prepared.
[0086]
Next, a tab portion made of aluminum foil (width: 3 mm, width: 3 mm; thickness: 0.120 mm) was formed on the outer edge of the surface of the current collector on the side where the electron conductive porous layers (thickness: 0.120 mm) of the produced anode and cathode were not formed. (Length 3 mm). The tab portion serves as a joining portion for joining the leads.
[0087]
Next, an aluminum ribbon (width 3 mm x length 20 mm x thickness 0.1 mm) serving as a lead was ultrasonically welded to the tab portion. Next, the anode and the cathode are opposed to each other, and a separator (16.5 mm × 18.5 mm, thickness: 0.05 mm, manufactured by Nippon Kogyo Kogyo Co., Ltd., trade name: “TF4050”) is arranged between the anode and the cathode. Then, a laminated body (element body) was formed in which the anode, the separator, and the cathode were in contact with each other in this order (non-bonded state). Next, after the sealant material is thermocompression-bonded to the lead portion, the laminate (element body) is put into a case formed of the same composite packaging film as that used in Example 1, and the lead portion is heat-sealed. did.
[0088]
Next, an electrolyte solution (a 1.2 mol / L solution of triethylmethylammonium tetrafluoride in propylene carbonate) was injected into the case, and vacuum sealing was performed to manufacture an electrochemical capacitor (electric double layer capacitor). Completed. At this time, the volume A [μL] of the electrolyte solution injected into the case was adjusted so that {A / (X + Y + Z)} = 1.23.
[0089]
(Comparative Example 3)
Except that the volume A [μL] of the electrolyte solution injected into the case was adjusted so that {A / (X + Y + Z)} = 1.44, the procedure and conditions were the same as those of the electrochemical capacitor of Example 2. An electrochemical capacitor was fabricated.
[0090]
(Comparative Example 4)
Except that the volume A [μL] of the electrolyte solution injected into the case was adjusted so that {A / (X + Y + Z)} = 0.89, the procedure and conditions were the same as those of the electrochemical capacitor of Example 2. An electrochemical capacitor was fabricated.
[0091]
[Characteristic evaluation test of electric double layer capacitor]
The following various characteristics were measured for the electric double layer capacitors of Example 1 and Example 2 and Comparative Examples 1 to 5.
[0092]
The charge / discharge measurement was performed using a charge / discharge test device (HJ-101SM6 manufactured by Hokuto Denko KK). First, a low-current charge of 0.5 C is performed, and a rise in voltage is monitored as electric charges are accumulated in the electric double layer capacitor. After the potential reaches 2.5 V, constant voltage charge (relaxation charge) is performed. The charging was terminated when the current became 1/10 of the charging current. The total charging time at this time (that is, charging time + relaxation charging time) depends on the capacitance of the cell. The discharge was also performed at a constant current of 0.5 C, and the final voltage was set to 0 V. After this test, the battery was charged with a current of 1 C. After the potential reached 2.5 V, the charging was switched to constant voltage charging, and the charging was terminated when the current became 1/10 of the charging current. The discharge was also performed at a constant current of 1C, and the final voltage was set to 0V. Charging was started again, and this was repeated 10 times.
[0093]
The capacitor capacity (electrostatic capacity of the cell of the electrochemical capacitor) was determined as follows. That is, the total discharge energy [W · s] is obtained from the discharge curve (discharge voltage−discharge time) as a time integral of discharge energy (discharge voltage × current (= 10 mA)), and capacitor capacity [F] = 2 × total discharge energy [ W · s] / (discharge start voltage [V]) ² Was used to determine the capacitance [F] of the capacitor of the evaluation cell.
[0094]
The volume energy density was determined as follows. That is, the energy density is obtained by dividing a value obtained by dividing the above total discharge energy [W · s] by the volume of the above-mentioned container into “volume energy density” [Wh · L] in this characteristic evaluation test. ^-1 ]).
[0095]
"Rate characteristics" (C2 / C1) were calculated based on the following definitions. That is, “C1” refers to an electrochemical capacitor having a capacitor capacity of αF and a discharge current value of α × 10 ^-3 A shows the capacitance when discharged at A. Further, “C2” means that the same electrochemical capacitor (electrochemical capacitor having a capacitance of αF) for which C1 was measured was discharged at a discharge current value of 100 × α × 10 ^-3 A shows the capacitance when discharged at A. The “rate characteristic” indicates a value (C2 / C1) obtained by dividing the above C2 by C1. An electrochemical capacitor having a large “rate characteristic” value can be evaluated as having excellent charge / discharge characteristics. For example, in the electrochemical capacitor of Example 1, since α = 0.054F, C1 is the capacitance measured when discharging at a current value of 54 μA, and C2 is discharging at a current value of 5.4 mA. This is the capacitance that is measured at that time.
[0096]
Table 1 shows the volume energy density, the capacitance (capacitance of the cell of the electrochemical capacitor), and the rate characteristics of each of the electrochemical capacitors of Example 1 and Example 2, and Comparative Examples 1 to 4.
[0097]
[Table 1]

[0098]
From these measurement results, it was confirmed that the results of Example 1 and Example 2 exhibited excellent rate characteristics as compared with each comparative example.
[0099]
Further, the values of X and Y of each of the electrochemical capacitors of Examples 1 and 2, and Comparative Examples 1 to 4 were determined by an ethanol impregnation method. Further, the separators of the electrochemical capacitors of Examples 1 and 2, and Comparative Examples 1 to 4 each used had a known Z value.
[0100]
【The invention's effect】
As described above, according to the present invention, there is a case where a case formed using a flexible film (for example, a composite packaging film) having a configuration that can be easily reduced in size and weight is used. Even so, it is possible to provide an electrochemical capacitor capable of reliably obtaining excellent charge / discharge characteristics. In particular, according to the present invention, it is possible to provide a thin film-shaped electrochemical capacitor (for example, an electrochemical capacitor having a thickness of 300 to 500 μm).
[Brief description of the drawings]
FIG. 1 is a front view showing a preferred embodiment of an electrochemical capacitor according to the present invention.
FIG. 2 is a developed view when the inside of the electrochemical capacitor shown in FIG. 1 is viewed from the normal direction of the surface of the anode 10.
FIG. 3 is a schematic cross-sectional view of the electrochemical capacitor shown in FIG. 1 taken along the line X1-X1 in FIG.
4 is a schematic cross-sectional view showing a main part when the electrochemical capacitor shown in FIG. 1 is cut along the line X2-X2 in FIG.
FIG. 5 is a schematic cross-sectional view showing a main part when the electrochemical capacitor shown in FIG. 1 is cut along the line YY in FIG.
6 is a schematic cross-sectional view showing an example of a basic configuration of a film serving as a constituent material of the case of the electrochemical capacitor shown in FIG.
FIG. 7 is a schematic cross-sectional view showing another example of the basic structure of a film as a constituent material of the case of the electrochemical capacitor shown in FIG.
8 is a schematic sectional view showing an example of a basic configuration of an anode of the electrochemical capacitor shown in FIG.
9 is a schematic cross-sectional view showing an example of a basic configuration of a cathode of the electrochemical capacitor shown in FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Electrochemical capacitor, 10 ... Anode, 12 ... Lead wire for anode, 14 ... Insulator, 20 ... Cathode, 22 ... Lead wire for cathode, 24 ... Insulator, 30 ... Electrolyte solution, 40 ... Separator, 50 ... Case , 60 ... prime field.

Claims (6)

A first plate-shaped electrode and a second plate-shaped electrode facing each other;
A plate-shaped separator disposed adjacent to between the first electrode and the second electrode;
An electrolyte solution;
A case formed from a film accommodating the first electrode, the second electrode, the separator, and the electrolyte solution in a sealed state;
Has,
The first electrode and the second electrode each include an electron conductive porous body as a constituent material,
The separator is made of an insulating porous material,
The electrolyte solution, at least a portion of which is contained in the first electrode and the second electrode, and inside the separator,
The volume A of the electrolyte solution filled in the case at 25 ° C. and 1 atm, the void volume X in the first electrode, the void volume Y in the second electrode, and the void volume in the separator Z satisfies a condition represented by the following formula (1);
An electrochemical capacitor, characterized in that:
1.0 ≦ {A / (X + Y + Z)} ≦ 1.4 (1) The electrochemical capacitor according to claim 1, wherein the thickness is 0.2 to 2.0 mm. 3. The electrochemical capacitor according to claim 1, wherein a thickness of the stacked body including the first electrode, the separator, and the second electrode is 0.1 to 0.4 mm. 4. The electrochemical capacitor according to any one of claims 1 to ^3, wherein the capacitance of the capacitor is 1 x ^{10-3 to} 1F. The film is formed of a composite packaging film having at least an innermost layer made of a synthetic resin that comes into contact with the electrolyte solution, and a metal layer disposed above the innermost layer. The electrochemical capacitor according to claim 1, wherein: The electrochemical case according to any one of claims 1 to 5, wherein the case is formed using at least a pair of the composite packaging films facing each other.

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