JP4350482B2 - Polarizable electrode for electric double layer capacitor and electric double layer capacitor using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polarizable electrode for an electric double layer capacitor, exhibiting good moldability and capable of realizing a high density or high cappacity electrode, and to provide an electric double layer capacitor employing it. <P>SOLUTION: The polarizable electrode for the electric double layer capacitor is composed of active carbon produced by activating a hard graphitization material (e.g. phenol resin) with steam wherein the active carbon has a medium particle size of 4-8 &mu;m in a particle size distribution measured by laser diffractometry and adsorption rate of benezene is 47.0-60% per weight of active carbon. The electric double layer capacitor employs a polarizable electrode of above constitution. <P>COPYRIGHT: (C)2004,JPO&amp;NCIPI

Description

  The present invention relates to a polarizable electrode for an electric double layer capacitor made of activated carbon and an electric double layer capacitor using the polarizable electrode.

  An electric double layer capacitor (electric double layer capacitor) uses electric energy accumulated in an electric double layer generated at an interface between a polarizable electrode and an electrolytic solution.

  Such an electric double layer capacitor has a farad-class large capacity and is excellent in charge / discharge cycle characteristics, and is therefore used in applications such as a backup power source for electric equipment and an in-vehicle battery.

  For example, as shown in FIG. 4, the electric double layer capacitor 1 has a structure including two polarizable electrodes, that is, a first electrode 2 and a second electrode 3 therein. The first electrode 2 and the second electrode 3 are separated by a separator 4.

  The first electrode 2 and a first current collector (hereinafter also referred to as a cap) 5 disposed outside the first electrode 2 constitute one electrode body 7 and function as an anode. On the other hand, the second electrode 3 and a second current collector (hereinafter also referred to as a case) 6 disposed outside the second electrode 3 constitute the other electrode body 8 and are configured to act as a cathode. Activated carbon having fine pores is suitably used for the first electrode 2 and the second electrode 3 constituting such an electric double layer capacitor 1 (see Patent Document 1).

  As shown in FIG. 5, the two polarizable electrodes 11 and 12 made of activated carbon constituting the electric double layer capacitor are impregnated with an electrolytic solution 15 made of a solvent and an electrolyte. As the electrolyte ions 16 and 17 are adsorbed and aggregated in the pores 18 and 19 of the activated carbon forming the two polarizable electrodes 11 and 12, one polarizable electrode 11 and the electrode body 13 form an anode. The other polarizable electrode 12 and the electrode body 14 constitute a cathode.

  The activated carbon forming the two electrodes can be considered to provide a field for the solvent and electrolyte ions to act electrochemically. Therefore, the physical properties and microstructure of activated carbon are one of the factors that greatly influence the performance of the electric double layer capacitor.

  As another example of the electric double layer capacitor described above, an electrode body formed into a sheet shape is bonded to a conductive foil-like metal body (hereinafter referred to as a conductive metal foil). 2. Description of the Related Art A capacitor is known that is formed by winding an electrode body that is affixed and integrated with an agent. In this case, as the conductive metal foil, for example, a foil made of a metal such as aluminum (Al) is not used, or the surface thereof is etched.

  By the way, as one of the characteristics required for an electrode for a high output capacitor (250 W class per single cell) intended for automobiles, there is a low internal resistance and a sufficient capacity enabling a large current to be taken out.

  As a method of increasing the capacity of the capacitor, there is a method of improving the capacity per electrode weight (F / g). However, when the capacity as a capacitor module is limited on the assumption that it is mounted on an automobile or the like. It is necessary to improve the capacity per electrode volume (F / cc) rather than the capacity per electrode weight (F / g). In other words, improving the capacity per electrode volume (F / cc) means that an improvement in the electrode forming density is required.

  In general, in order to improve the forming density of the electrode, a method of improving the density of the activated carbon itself without reducing the capacity per weight, or a method of creating a close packing structure when forming the electrode is widely known. .

  As the former method, ie, a method for increasing the density of activated carbon itself, for example, an easily graphitized raw material is used as an activated carbon raw material, and a carbon raw material obtained by carbonization at a temperature of 1000 ° C. or less in an inert atmosphere is alkali metal. The use of activated carbon or the like obtained by chemical activation with a hydroxide such as is disclosed in Patent Document 1.

  However, the manufacturing process using these chemical activations is difficult to control at the time of activation, and a process for cleaning the chemicals used to the level that does not affect the operation of the capacitor after activation is necessary. There are a lot of issues in terms.

  On the other hand, as the activated carbon that is stably produced, activated carbon activated by using a gas such as water vapor instead of the above chemical activation is known. At that time, a raw material obtained by carbonizing a hardly graphitized raw material at a temperature of about 1000 ° C. in an inert atmosphere is used as the carbon raw material. In this method, since the non-graphitizing raw material that is relatively easily activated is used, pore formation of the activated carbon proceeds excessively, and as a result, the density of the activated carbon itself tends to decrease.

  As the latter method, that is, a method of creating a close packing structure at the time of forming an electrode, a method of densifying the electrode sheet by controlling a roll rolling load or the like when forming the electrode sheet (see Patent Document 2), Examples include a method of controlling the particle size of activated carbon, which is a main component (see Patent Document 3).

  However, the electrode densified by any of the above methods may cause significant molding defects such as cracks or tears in the molded sheet, or decrease the electrolyte penetration rate in the electrolyte impregnation process during capacitor assembly. Insufficient impregnation may occur.

Moreover, since the above-described moldability and electrode density are physical property values that can be clearly evaluated only after being processed into a sheet shape, there is also a problem that it is difficult to judge whether the raw material activated carbon is good or bad in advance. .
Japanese Patent Laid-Open No. 9-320906 JP 2000-277391 A JP 2001-52972 A

  In view of the above circumstances, the present invention provides a polarizable electrode for an electric double layer capacitor that has good moldability and can increase the density and capacity of the electrode, and an electric double layer capacitor using the same The purpose is to do.

In order to solve the above problems, the present invention comprises activated carbon obtained by activating a non-graphitizable raw material with water vapor, and the activated carbon has a central particle size of 4 μm or more and 7.5 μm or less as observed by a laser diffraction method. And the benzene adsorption rate is 47.0% or more and 60% or less per weight of the activated carbon, and after kneading the activated carbon, the conductive filler and the binder into a mixture, the sheet-like member is formed by rolling the mixture. There is provided a polarizable electrode for an electric double layer capacitor, wherein the polarizable electrode for an electric double layer capacitor is formed by adding 5% by weight of the binder in the mixture .

  If it is activated carbon obtained by activating a non-graphite raw material (for example, the phenolic resin of the embodiment) with water vapor, a laser diffraction method (for example, a measurement method using a Shimadzu SALD-3000S device described in detail in the embodiment) ) With different benzene adsorption rates measured by weight differences in the central particle size of the particle size distribution observed by (3) and the adsorption of benzene vapor on activated carbon.

When the central particle size of the particle size distribution is less than 4 μm, the electrode sheet strength monotonously decreases as the central particle size decreases. On the other hand, when the center particle diameter exceeds 7.5 μm, the electrode sheet strength is significantly reduced as the center particle diameter increases. On the other hand, activated carbon having a particle size distribution with a central particle size of 4 μm or more and 7.5 μm or less is preferable because an extremely high electrode sheet strength of around 5 kgf / cm ² can be secured.

Activated carbon having a benzene adsorption rate of 47.0% or more and 60% or less per benzene weight is also desirable because it provides an extremely high electrode sheet strength of around 5 kgf / cm ² . It was confirmed that the electrode sheet strength tends to decrease when the content is lower than 47.0% or exceeds 60%. If the activated carbon has a particle size distribution center particle size or benzene adsorption rate within the above range, it can have a relatively high electrode sheet density exceeding 0.630 g / cc.

Therefore, relatively high electrode sheet strength can be obtained by using activated carbon having a central particle size distribution of 4 μm to 7.5 μm and a benzene adsorption rate of 47.0% to 60% per weight of the activated carbon. Therefore, for example, when manufacturing a polarizable electrode used by bonding to an Al foil or the like, it has good workability and can reduce the manufacturing cost. Contributes to higher capacity.

The present invention also provides an electric double layer capacitor comprising an electrode body comprising a current collector and a polarizable electrode, a separator, and an electrolyte solution, wherein the polarizable electrode is activated carbon obtained by activating a non-graphite raw material with water vapor. The activated carbon has a central particle size of 4 μm or more and 7.5 μm or less and a benzene adsorption rate of 47.0% or more and 60% or less per weight of the activated carbon observed by a laser diffraction method, after the activated carbon, conductive filler and mixtures by kneading a binder, Ri Na to form a sheet-shaped member by rolling of the mixture, the amount of the binder in said mixture Ru 5 wt% der An electric double layer capacitor is provided.

According to such a configuration, the activated carbon forming the polarizable electrode of the electric double layer capacitor has a central particle size (4 μm or more and 7.5 μm or less) of the particle size distribution having the above-mentioned range and a benzene adsorption rate (47. 0% or more and 60% or less), and can maintain a capacity maintenance rate of around 90% even after 2000 hours, so that it is possible to provide an electric double layer capacitor that can exhibit excellent reliability even during long-term use. Become.

  The polarizable electrode for an electric double layer capacitor according to the present invention comprises activated carbon having a central particle size distribution of 4 μm or more and 8 μm or less and a benzene adsorption rate of 47.0% or more and 60% or less per weight of the activated carbon. It is possible to have both relatively high electrode sheet strength and electrode sheet density, which results in good formability of the polarizable electrode.

  The good formability of the polarizable electrode described above improves the work stability when handling the polarizable electrode, thereby contributing to the reduction of manufacturing costs, and the high electrode sheet density contributes to the production of a highly polarizable electrode. Contribute.

  In addition, the electric double layer capacitor according to the present invention can have a high value of about 90% in capacity retention after 2000 hours by using the polarizable electrode having the above-described configuration.

  Therefore, according to the present invention, it is possible to provide a polarizable electrode for an electric double layer capacitor and an electric double layer capacitor which can be reduced in cost and have high performance and excellent long-term reliability.

  The activated carbon constituting the polarizable electrode for an electric double layer capacitor according to the present invention is formed by activating a non-graphite raw material with water vapor.

  Here, the term “non-graphitizable raw material” is used to generically refer to materials made of organic compounds that are difficult to graphitize. The difficulty in graphitization means that a graphite structure is hardly formed even by a baking treatment at 3000 ° C. or higher. Formation of the graphite structure can be confirmed, for example, by having a clear peak at 2θ around 25 ° in the X-ray diffraction pattern.

  The activated carbon constituting the polarizable electrode for an electric double layer capacitor according to the present invention is preferably obtained by a production method based on the technique described below.

  First, the raw material used when manufacturing the activated carbon which concerns on this invention is demonstrated. As the raw material of the activated carbon of the present invention, a non-graphitizable material that is difficult to graphitize is suitable. A graphitization catalyst may be added during graphitization. Examples of organic compounds that are difficult to graphitize to form a non-graphitizable material include, for example, furfuryl alcohol that is an aromatic compound, polycarbonate, cellulose, phenol resin, an epoxy resin that is an aliphatic compound, PVDF (polyvinylidene fluoride) , Polyvinyl alcohol, nylon, polypropylene and the like.

  Using such raw materials, the activated carbon of the polarizable electrode for an electric double layer capacitor according to the present invention can be produced by the following procedure. Here, a method is described in which a phenol resin is used as the non-graphitizable material, heat treatment is performed at a temperature at which a graphite structure is generated, and then activation treatment is performed with water vapor.

The heat treatment performed at the temperature at which the graphite structure is formed is usually 400 to 1000 ° C., preferably 500 to 800 ° C., more preferably under a non-oxidizing atmosphere, for example, a nitrogen gas (N ₂ gas) stream. The temperature is 500 to 700 ° C. The treatment time is usually 24 hours or less, preferably 1 to 10 hours, more preferably 2 to 5 hours. Other treatment conditions can be appropriately determined according to the raw materials used and the type of activated carbon for electrodes to be produced.

  Steam activation can be performed by a normal method. In a preferred embodiment, steam activation is performed as follows. That is, the washing bottle containing pure water is kept at room temperature to 100 ° C., preferably 80 ° C., nitrogen gas is allowed to flow through the bottle, and activation is performed with the nitrogen gas containing water vapor. Specifically, the temperature is raised in a nitrogen stream up to 800 to 1000 ° C., preferably up to 900 ° C., and when a predetermined temperature (for example, 800 ° C.) is reached, a mixed gas of nitrogen / water vapor is used for 5 minutes to Activation for 10 hours.

  The activated carbon of the polarizable electrode for an electric double layer capacitor according to the present invention can be obtained by pulverizing the activated carbon prepared as described above to a predetermined particle size using a pulverization method such as a jet mill or a ball mill.

  Next, using the obtained activated carbon, a polarizable electrode for an electric double layer capacitor can be produced by an ordinary method. Examples of a method for forming a sheet-like polarizable electrode include the following methods.

  After knead | mixing the activated carbon obtained from the phenol resin mentioned above, the graphite powder as a conductive filler, and Teflon (trademark) as a binder in a predetermined ratio (for example, 90: 5: 5 by weight ratio), rolling Then, a sheet-like member having a thickness of 150 μm is formed, and then this sheet-like member is punched into a circle to form a polarizable electrode having a diameter of 20 mm.

  Next, as shown in FIG. 4, a structure in which a separator is sandwiched between two sheet-like polarizable electrodes 2 and 3 is placed in a case 6 made of a conductive material and forming a cathode, and an electrolytic solution is injected. After that, the cap 5 made of a conductive material and forming the anode is placed, and then the ends of the case 6 and the cap 5 are crimped and sealed through the packing 9 of the insulating material to produce the electric double layer capacitor 1. can do.

  The central particle size, which is an index of activated carbon, can be determined from a particle size distribution obtained by a laser diffraction method (measurement method using a SALD-3000S apparatus manufactured by Shimadzu Corporation). The benzene adsorption rate can be determined by a measurement method defined in JIS standard K1474-1991.

  The electrode sheet strength, which is an index of the performance of the capacitor, can be determined by measuring the tensile strength using, for example, EZ Test-100N manufactured by Shimadzu Corporation. Moreover, an electrode sheet density can be calculated | required by measuring an apparent density, for example using a micrometer.

The capacity retention rate after endurance is a numerical value expressed as a percentage obtained by dividing the electrostatic capacity after performing a 2.5 V continuous voltage application test in a 45 ° C. environment for 2000 hours by the electrostatic capacity before voltage application. is there. Here, a predetermined electrolytic solution (for example, propylene carbonate solution of triethylmethylammonium tetrafluoroborate: TEMA.BF ₄ / PC, concentration 1.8 mol / l) is used for the electrostatic capacity, and a predetermined voltage and current (for example, And charging / discharging is repeated at a charging voltage of 2.5 V and a charging current of 5 mA), and can be obtained from the discharge energy.

  The present invention will be described more specifically with reference to the following examples. However, the present invention is not limited to the following examples.

(Example 1)
The activated carbon powder according to this example was produced by the following procedure.
(1) The phenol resin granulated so as to have a particle size of about 3 mm was carbonized by holding it in a nitrogen stream at 900 ° C. for 2 hours.

  (2) The obtained raw material carbon is heated again in a nitrogen stream, and when reaching 800 ° C., a nitrogen mixed gas containing 5% water vapor and 5% carbon dioxide is circulated to 900 ° C. (hereinafter, activation temperature). The activation process was performed by holding for 2 hours (hereinafter referred to as activation time).

  (3) The obtained activated carbon is allowed to cool, and then a ball mill pulverizer using high-purity alumina balls is used, the rotation speed of the pulverizer is 15 rpm, and the pulverization is performed for 180 hours (hereinafter referred to as pulverization time). An activated carbon powder according to this example was obtained.

  The central particle diameter of the produced activated carbon was determined from the particle size distribution obtained by a laser diffraction method (measurement method using a SALD-3000S apparatus manufactured by Shimadzu Corporation).

  Moreover, the benzene adsorption rate of the produced activated carbon was calculated | required with the measuring method defined by K1474-1991 of JIS specification.

  5% Teflon (registered trademark) (made by Mitsui DuPont Fluorochemical) 6J and 5% Denka Black (registered trademark, manufactured by Denki Kagaku Kogyo) as a binder by weight ratio are added to this activated carbon. A polarizable electrode having a thickness of 150 μm measured with a meter was used. In addition, the polarization electrode was vacuum-dried at 150 ° C. for 4 hours, and then the weight was measured to obtain a current density.

The electrolyte is a 1.8 M (C ₂ H ₅ ) ₃ CH ₃ N · BF ₄ PC solution, which is charged with a charging voltage of 2.5 V and a charging current of 5 mA for 2 hours, and the discharge energy thereof. From this, the capacitance was determined. The capacity retention rate after endurance was expressed by dividing the electrostatic capacity after applying a constant voltage of 2.5 V for 2000 hours in a 45 ° C. environment by the electrostatic capacity before applying the voltage, and expressing the value as a percentage. It is a numerical value.

  Table 1 collectively shows the numerical values regarding the center particle diameter and benzene adsorption rate of the activated carbon obtained in Example 1, the electrode density of the polarizable electrode, and the capacity retention rate after durability.

(Examples 2 to 6)
In this example, the grinding time was 130 hours (Example 2), 110 hours (Example 3), 80 hours (Example 4), 50 hours (Example 5), and 30 hours (Example 6). Except for the above, activated carbon was prepared in the same manner as in Example 1, and the central particle size and benzene adsorption rate of the activated carbon, the electrode density of the polarizable electrode, and the capacity retention rate after durability were determined in the same manner. These values are also shown in Table 1.

(Example 7)
In this example, activated carbon was produced by the same method as in Example 1 except that the activation time was changed to 0.5 hour and the pulverization time was changed to 80 hours, respectively. The electrode density of the polarizable electrode and the capacity retention rate after durability were determined. These values are also shown in Table 1.

(Examples 8 to 12)
In this example, the activation time is 0.75 hours (Example 8), 1.0 hour (Example 9), 1.25 hours (Example 10), 2.5 hours (Example 11). Activated carbon was prepared in the same manner as in Example 7 except that the time was 0 hour (Example 12), and the central particle size and benzene adsorption rate of the activated carbon, electrode density of the polarizable electrode, and capacity maintenance after durability were maintained in the same manner. The rate was determined. These values are also shown in Table 1.

(Comparative Example 1)
In this example, activated carbon was prepared by the same method as in Example 1 except that the pulverization time was changed to 300 hours, and the center particle size and benzene adsorption rate of the activated carbon, the electrode density of the polarizable electrode, and the durability after the same method. The capacity maintenance rate was obtained. These values are shown in Table 2.

(Comparative Examples 2 to 5)
In this example, the grinding time was the same as Comparative Example 1 except that the grinding time was 250 hours (Comparative Example 2), 20 hours (Comparative Example 3), 18 hours (Comparative Example 4), and 15 hours (Comparative Example 5). Activated carbon was produced by the method, and the center particle size and benzene adsorption rate of the activated carbon, the electrode density of the polarizable electrode, and the capacity retention rate after durability were obtained by the same method. These values are also shown in Table 2.

(Comparative Example 6)
In this example, activated carbon was prepared in the same manner as in Comparative Example 1 except that the activation temperature was changed to 850 ° C., the activation time was changed to 0.25 hours, and the pulverization time was changed to 80 hours. The center particle size and the benzene adsorption rate, the electrode density of the polarizable electrode, and the capacity retention rate after durability were determined. These values are also shown in Table 2.

(Comparative Examples 7 to 10)
In this example, the activation temperature is 800 ° C., the activation time is 0.25 hours (Comparative Example 7), the activation temperature is 850 ° C., the activation time is 0.5 hours (Comparative Example 8), the activation temperature is 900 ° C., and the activation time. Activated carbon was prepared in the same manner as in Comparative Example 6, except that the activation temperature was 900 ° C. and the activation time was 4.5 hours (Comparative Example 10). The center particle size and the benzene adsorption rate, the electrode density of the polarizable electrode, and the capacity retention rate after durability were determined. These values are also shown in Table 2.

FIG. 1 is a graph showing the relationship between the center particle size or benzene adsorption rate and the electrode sheet strength. From FIG. 1 (a), it can be seen that an extremely high electrode sheet strength of around 5 kgf / cm ² can be secured if the activated carbon has a particle size distribution with a center particle size of 4 μm or more and 8 μm or less. When the center particle size is less than 4 μm, the electrode sheet strength decreases monotonously as the center particle size decreases. When the center particle size exceeds 8 μm, the electrode sheet strength decreases significantly as the center particle size increases. It ’s not good.

From FIG. 1 (b), it can be seen that if the benzene adsorption rate is 47.0% or more and 60% or less per weight of the activated carbon, an extremely high electrode sheet strength of about 5 kgf / cm ² can be secured. When the benzene adsorption rate is lower than 47.0% or exceeds 60%, the electrode sheet strength tends to decrease, which is not good.

  FIG. 2 is a graph showing the relationship between the center particle size or benzene adsorption rate and the electrode sheet density. FIG. 2A shows that the electrode sheet density tends to monotonously decrease as the central particle size of the activated carbon increases. Further, from FIG. 2B, it was found that the electrode sheet density has the same tendency as the center particle size with respect to the benzene adsorption rate.

The range of the center particle size (4 μm or more and 8 μm or less) or the benzene adsorption rate (47.0% or more and 60% or less per weight of activated carbon) in which an extremely high electrode sheet strength of about 5 kgf / cm ² is obtained, which is apparent from FIG. It can be confirmed from the graph of FIG. 2 that it is possible to have a relatively high electrode sheet density exceeding 0.630 g / cc.

  1 and 2, the electric double layer capacitor using activated carbon having a particle size distribution with a central particle size of 4 μm or more and 8 μm or less and a benzene adsorption rate of 47.0% or more and 60% or less per weight of the activated carbon. It was confirmed that the polarizable electrode has a relatively high electrode sheet strength and electrode sheet density.

  FIG. 3 is a graph showing the relationship between the center particle size or benzene adsorption rate and the capacity retention rate after 2000 hours. From FIG. 3A, it is clear that when the center particle size of the particle size distribution is 4 μm or more, the capacity retention rate after 2000 hours can be as high as about 90%. In the region where the center particle size is less than 4 μm, the capacity retention rate decreases rapidly as the center particle size decreases, which is not good.

  From FIG. 3 (b), it can be seen that if the activated carbon has a benzene adsorption rate of 47.0% or more and 60% or less per weight of benzene, the capacity retention rate after 2000 hours can secure a high value of around 90%. When the benzene adsorption rate is lower than 47.0% or exceeds 60%, the capacity retention rate tends to decrease, which is not good.

  From the results of FIG. 3, the polarizability for an electric double layer capacitor using activated carbon having a central particle size of particle size distribution of 4 μm to 8 μm and a benzene adsorption rate of 47.0% to 60% per weight of the activated carbon. It has been clarified that an electric double layer capacitor using electrodes can maintain a high capacity retention rate of about 90% even after 2000 hours of charge and discharge.

It is a graph which shows the relationship between a center particle size or a benzene adsorption rate, and an electrode sheet intensity | strength. It is a graph which shows the relationship between a center particle size or a benzene adsorption rate, and an electrode sheet density. It is a graph which shows the relationship between a center particle size or a benzene adsorption rate, and the capacity | capacitance maintenance factor after 2000 hours. It is a figure which shows an example of an electrical double layer capacitor. It is a conceptual diagram which shows the state by which the ion in electrolyte solution is adsorb | sucked to an electrode.

Explanation of symbols

1 electric double layer capacitor,
2 First electrode (polarizable electrode),
3 Second electrode (polarizable electrode),
4 separator,
5 First current collector (cap),
6 Second current collector (case),
7 Electrode body (anode),
8 electrode body (cathode),
11, 12 minute polar electrode,
13, 14 electrode body,
15 electrolyte,
16, 17 Electrolyte ions,
18, 19 Pore.

Claims (2)

It consists of activated carbon obtained by activating a non-graphite raw material with water vapor, and the activated carbon has a central particle size of 4 μm or more and 7.5 μm or less observed by a laser diffraction method, and a benzene adsorption rate per weight of the activated carbon. 47.0% or more and 60% or less, and the polarizability for an electric double layer capacitor formed by kneading the activated carbon, the conductive filler and the binder into a mixture, and then forming a sheet-like member by rolling the mixture . An electrode,
A polarizable electrode for an electric double layer capacitor, wherein the amount of the binder added to the mixture is 5% by weight . In an electric double layer capacitor composed of an electrode body composed of a current collector and a polarizable electrode, a separator and an electrolyte,
The polarizable electrode is made of activated carbon obtained by activating a non-graphite raw material with water vapor, and the activated carbon has a central particle size of 4 μm or more and 7.5 μm or less as observed by a laser diffraction method, and has benzene adsorption. rate is 60% or less 47.0% more per weight of activated carbon, the activated carbon, after a conductive filler and a binder and kneaded to a mixture, Ri Na to form a sheet-shaped member by rolling of the mixture electric double layer capacitor amount of the binder in the mixture and wherein the 5 wt% der Rukoto.

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