JP2012038982A - Method of manufacturing electric double layer capacitor electrode and electric double layer capacitor electrode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing the electrode of an electric double layer capacitor having a high capacity in a short time.SOLUTION: In an electrolytic solution of phosphoric acid or sulphuric acid, a rectangular wave having a lower limit potential from 0.0 V to +0.3 V for a reversible hydrogen electrode used as a reference electrode and an upper limit potential in the range from +0.5 V to +0.7 V is applied to a carbon substrate, i.e. the electrode body of an electric double layer capacitor, for 10-60 sec of the upper limit potential holding time until a charge amount of 3,800-120,000C flows per 1 mol of carbon contained in the carbon substrate.

Description

  The present invention relates to a method for producing an electric double layer capacitor electrode and an electric double layer capacitor electrode.

  An electric double layer capacitor is a power storage device that charges and discharges electricity by adsorbing and desorbing ions on the surface of an electrode made of a porous conductive material. It can be charged in a short time, charged and discharged with a large current, and has high output. Excellent performance such as long life of charge / discharge cycles.

In recent years, electric double layer capacitors have been desired to have higher performance, in particular, higher capacity per unit volume of electrodes in order to expand applications. Conventionally, as an electrode, activated carbon whose specific surface area has been increased by forming pores by baking carbon fiber or resin at a high temperature and further activating with carbon dioxide or alkali at a high temperature has been used. However, there is a limit to increasing the capacity by increasing the pores. This is because the capacitance per volume decreases conversely when the number of pores is increased too much. In fact, it was common to use activated carbon of about 1500 m ² / g.

  Therefore, an electrolytic activation method has been proposed. For example, Patent Document 1 discloses a porous carbon material obtained by mixing an easily graphitizable carbon material with an alkali carbonate at a mass-based mixing ratio of 1: 1 to 1: 8 and heat-treating at a temperature of 700 to 1000 ° C. A method for manufacturing an electric double layer capacitor is described in which an electrode is formed using an electrode material, and is then subjected to electrolytic activation after cell assembly. According to such a manufacturing method, the capacitance per volume is described. It is described that an electric double layer capacitor having a high yield and a high yield can be easily and inexpensively manufactured industrially.

  Patent Document 2 discloses a step of obtaining an electric double layer capacitor in which a nonporous carbonaceous electrode having microcrystalline carbon similar to graphite is immersed in an organic electrolytic solution; A step of charging at a constant current until the voltage reaches a predetermined voltage that is equal to or higher than the capacitance expression voltage and lower than the rated voltage; it is considered that solute ions in the organic electrolyte are uniformly adsorbed on the surface of the microcrystalline carbon at the predetermined voltage. A step of charging at a constant voltage for a predetermined time; a step of charging at a constant current until the voltage between the electrodes reaches a predetermined voltage not lower than the rated voltage and not higher than the decomposition voltage of the electrolytic solution; and the solute ions in the organic electrolytic solution are minute at the predetermined voltage. A method of activating an electric double layer capacitor, which includes a step of charging at a constant voltage for a predetermined time which is considered to be uniformly inserted between layers of crystalline carbon. According to such a method, Even in the case of using a carbonaceous electrode of the same type, it has been described as remarkable effect that reduction of the internal resistance with improved capacitance density can be achieved.

JP 2006-278588 A Japanese Patent No. 3884060

  However, if electrolytic activation is performed after assembling the cells as in the method described in Patent Document 1 or 2, a decomposition product of the electrolytic solution may be released into the electrolytic solution, which may increase the diffusion resistance of adsorbed ions. Also, in order to avoid this, in order to perform electrolytic activation before assembling the cells, it is necessary to perform the electrolytic activation in an atmosphere having a dew point of −60 ° C. or lower in order to use an organic electrolytic solution while avoiding mixing of moisture. There are large facilities such as a dry room.

  Therefore, an object of the present invention is to provide a method for obtaining an electric double layer capacitor electrode having a higher capacitance than the conventional one. In addition, the decomposition product of the electrolytic solution is not released into the electrolytic solution and the diffusion resistance of the adsorbed ions does not increase, and it is not necessary to use a large facility such as a dry room in order to avoid the mixing of moisture. It is an object of the present invention to provide a method for producing an electric double layer capacitor electrode that can increase the capacitance of a carbon substrate only by applying for a short time.

The inventor has intensively studied to solve the above-mentioned problems, and has completed the present invention.
The present invention includes the following (1) to (9).
(1) A method for producing an electric double layer capacitor electrode, comprising a step of applying a potential that forms a rectangular wave to a carbon substrate in an electrolytic solution.
(2) The method for producing an electric double layer capacitor electrode according to (1), wherein the voltage is applied to the carbon substrate in the electrolytic solution at 150 to 220 ° C.
(3) The method for producing an electric double layer capacitor electrode according to (1) or (2), wherein the electrolytic solution is phosphoric acid or sulfuric acid.
(4) The electric secondary electrode according to any one of (1) to (3), wherein a lower limit potential of the potential forming the rectangular wave is 0.0 to +0.3 V with respect to the reversible hydrogen electrode used as a reference electrode. Manufacturing method of multilayer capacitor electrode.
(5) The upper limit potential of the potential that forms the rectangular wave is +0.5 to +0.7 V with respect to the reversible hydrogen electrode used as a reference electrode, according to any one of (1) to (4) above Manufacturing method of multilayer capacitor electrode.
(6) Manufacture of the potential double layer capacitor electrode according to any one of (1) to (5), wherein the charge is applied until a charge amount of 3,800 to 120,000 C flows per mol of carbon contained in the carbon substrate. Method.
(7) The method for producing an electric double layer capacitor electrode according to any one of (1) to (6), wherein the holding time of the upper limit potential of the potential forming the rectangular wave is 10 to 60 seconds.
(8) An electric double layer capacitor electrode obtained by the method for producing an electric double layer capacitor electrode according to any one of (1) to (7).
(9) An electric double layer capacitor having the electric double layer capacitor electrode according to (8) above.

  According to the present invention, it is possible to obtain an electric double layer capacitor electrode having a higher capacitance than conventional ones. In addition, the production method of the present invention can be applied to a powdery carbon raw material formed with a binder or a carbon material that is not powdery, regardless of the shape of the carbon substrate used for the electrode.

  Further, the present invention is preferably a method for producing an electric double layer capacitor electrode comprising a step of applying a potential forming a rectangular wave to a carbon substrate in the electrolyte at 100 ° C. or higher, preferably 150 to 220 ° C. According to such a preferable production method of the present invention, since the potential is applied before assembling the cell, the decomposition product of the electrolytic solution is not released into the electrolytic solution and the diffusion resistance of the adsorbed ions does not increase. In addition, it is not necessary to use a large facility such as a dry room in order to avoid the mixing of moisture, and the capacitance of the carbon substrate can be increased only by applying for a short time.

FIG. 1 is a diagram showing an example of a potential forming a rectangular wave applied to a carbon base material in the applying step according to the present invention. FIG. 2 is a schematic cross-sectional view showing a specific example of an apparatus that can be used to apply a rectangular wave potential to a carbon substrate. FIG. 3 is a diagram illustrating a cross-sectional shape of the electric double layer capacitor. FIG. 4 is a diagram showing the relationship between the bulk density of the porous carbon substrate and the capacitance in Examples and Comparative Examples. FIG. 5 is a diagram showing the relationship between the upper limit potential or the lower limit potential and the capacitance in the example. FIG. 6 is a graph showing changes in the charge amount (accumulated charge amount increase rate per unit time) of the porous carbon substrate in the example. FIG. 7 is a diagram showing the relationship between the charge amount and the bulk density in the example.

The present invention will be described.
The present invention is a method for producing an electric double layer capacitor electrode, comprising a step of applying a rectangular wave potential to a carbon substrate in an electrolytic solution.
In the present invention, the step of applying a rectangular wave potential to the carbon substrate in the electrolytic solution is also referred to as an application step below.

First, the potential that forms a rectangular wave in the application step will be described.
The potential that forms a rectangular wave in the applying step means a rectangular wave-like potential that changes regularly and instantaneously between two levels of potential when the time is plotted on the horizontal axis and the potential is plotted on the vertical axis. For example, as shown in FIG. FIG. 1 is a diagram showing an example of a potential forming a rectangular wave applied to a carbon substrate in the application step, in which the horizontal axis is time and the vertical axis is a potential (RHE) with respect to a reversible hydrogen electrode (unit: V).

  Further, as shown in FIG. 1, a high-level potential in a rectangular wave potential is defined as an upper limit potential, and a low-level potential is defined as a lower limit potential. Here, the upper limit potential or the lower limit potential may not always be constant. That is, in FIG. 1, the upper limit potential is constant at +0.7 V with respect to the reversible hydrogen electrode as the reference electrode, and the lower limit potential is constant at +0.1 V. For example, from the upper limit potential of +0.7 V to +0.1 V After changing to the lower limit potential, it may be changed to the upper limit potential of + 0.5V, and further to the lower limit potential of + 0.2V.

  In addition, it is preferable that both the upper limit potential and the lower limit potential are potentials with respect to the reversible hydrogen electrode which is a reference electrode. In this case, when applying a rectangular wave potential in the present invention, the reversible hydrogen electrode is used as a reference electrode soaked in the electrolyte.

  Moreover, it is preferable that the said upper limit electric potential is + 0.5- + 0.7V with respect to the reversible hydrogen electrode used as a reference electrode, and it is further more preferable that it is + 0.6- + 0.7V. This is because the capacitance of the carbon base material to which the potential forming the rectangular wave is applied is further increased when the upper limit potential is such.

  The lower limit potential is preferably 0.0 to +0.3 V, more preferably 0.0 to +0.2 V, and more preferably 0.0 to +0. More preferably, it is 1V. This is because the capacitance of the carbon base material to which the potential forming the rectangular wave is applied is further increased when the upper limit potential is such.

  Further, the upper limit potential is +0.5 to +0.7 V for a reversible hydrogen electrode used as a reference electrode, and the lower limit potential is 0.0 to +0. 3V is preferred. This is because the capacitance of the carbon base material to which a rectangular wave potential is applied is further increased when the upper limit potential and the lower limit potential are satisfied.

  As shown in FIG. 1, the time during which the upper limit potential is continued is defined as the upper limit potential holding time, and the time during which the lower limit potential is maintained is defined as the lower limit potential holding time. Here, the upper limit potential holding time and the lower limit potential holding time may not always be constant.

  The upper limit potential holding time is not particularly limited, but is preferably 10 to 60 seconds, more preferably 20 to 50 seconds, more preferably 30 to 45 seconds, and 35 to 40 seconds. More preferably it is. This is because the charge amount of the carbon base material is sufficient when it is such an upper limit potential holding time.

  The lower limit potential holding time is not particularly limited, but is preferably 10 to 60 seconds, more preferably 20 to 50 seconds, more preferably 30 to 45 seconds, and 35 to 40 seconds. More preferably it is. This is because the charge amount of the carbon substrate is sufficient when the lower limit potential is maintained.

Further, per 1 mol of carbon contained in the carbon base material, preferably 3,800 to 120,000 C, more preferably 20,000 to 60,000 C, more preferably 30,000 to 46,000 C, still more preferably 38, Apply until a charge amount of about 000 C flows. Increasing the amount of charge to be applied oxidizes the surface of the carbon substrate, and part of it becomes CO ₂ , resulting in lower density and lower strength, making it difficult to maintain the structure as an electrode. Even if it is applied until such a charge amount flows, the decrease in strength is small.

Next, a method of applying a rectangular wave potential as described with reference to FIG. 1 to the carbon substrate will be described with reference to FIG. Although the method of applying the rectangular wave potential as described above to the carbon substrate in the electrolyte is not particularly limited, it is preferably performed using a device shown as a specific example.
FIG. 2 is a schematic cross-sectional view showing a specific example of an apparatus that can be used to apply a rectangular wave potential to a carbon substrate.
In FIG. 2, the carbon substrate 10 is accommodated in a pocket of the working electrode 20. The working electrode 20, the counter electrode 22, and the reversible hydrogen electrode 24 are immersed in the electrolytic solution 15 stored in the container 5, and each is connected to a potentiostat 26. Here, the working electrode 20 is disposed so that all of the pocket portions containing the carbon substrate 10 are immersed in the electrolytic solution 15. Further, the distance between the electrodes is adjusted so that the current flowing through the working electrode 20 and the counter electrode 22 does not change. If the distance between the poles changes while applying a rectangular wave potential to the carbon substrate, the ionic resistance changes and the current changes. Therefore, the electrodes are fixed and the distance is adjusted to be constant.
The current flowing between the working electrode 20 and the counter electrode 22 can be controlled by the potentiostat 26 so that the potential between the working electrode 20 and the reversible hydrogen electrode 24 becomes a potential forming a desired rectangular wave. .

Next, the electrolytic solution in the application step will be described. In the applying step, a potential that forms the rectangular wave is applied to the carbon base material in an electrolytic solution described below.
In the application step, the electrolytic solution is not particularly limited, and is preferably substantially free of water, preferably stable at 100 ° C. or higher and having a decomposition voltage larger than the voltage at the time of application. Here, the decomposition voltage refers to a voltage at which the current between the sample electrode and the reference electrode increases and the electrochemical decomposition of the electrolytic solution is started.
Further, in the applying step, it is preferable to apply a potential that forms the rectangular wave to the carbon base material in a state where the electrolytic solution is 100 ° C. or higher, preferably 150 to 220 ° C., more preferably 160 to 190 ° C. This is because moisture can be removed from the electrolytic solution. In addition, since the potential is applied before assembling the cell, the decomposition product of the electrolytic solution is not released into the electrolytic solution and the diffusion resistance of the adsorbed ions does not increase. This is because there is no need for advanced humidity management using large-scale equipment or a glove box, and the capacitance of the carbon base material can be increased only by applying for a short time. Phosphoric acid or sulfuric acid is stable at 100 ° C. or higher, and the decomposition voltage is higher than the applied voltage at the time of activation, so that it can be preferably used as an electrolyte.

Next, the carbon substrate in the application step will be described.
In the application step, the carbon substrate is not particularly limited as long as it is a material mainly composed of carbon. The shape is not limited, and a powdery carbon raw material formed with a binder or a lump-like carbon material that is not powdery can be used.
Examples of the carbon substrate include activated carbon, carbon fiber, pulp, resin, coal-based or petroleum-based pitch coke, mesophase pitch-based carbon fiber, mesocarbon microbead, needle coke, carbon black, infusible vinyl chloride, and carbon nanotube. Etc. can be used as the carbon substrate. Here, if the carbon fiber is crimped, it can be preferably used because it hardly shrinks after heat treatment and the pore volume tends to increase. Examples of the pulp include hardwood bleached kraft pulp (LBKP), hardwood unbleached kraft pulp (LUKP), softwood bleached kraft pulp (NBKP), softwood unbleached kraft pulp (NUKP), cotton pulp, hemp pulp and the like. It is done. Examples of the resin herein include phenol resin, furan resin, epoxy resin, unsaturated polyester resin, polyimide resin, urea resin, and melamine resin.

  Moreover, the said carbon base material can also be used in mixture of multiple types. For example, a carbon base material obtained by mixing carbon fiber subjected to crimping treatment with pulp is preferable because it has high strength and has high shape retention. In particular, when hemp pulp is used as the pulp, the shape retention is excellent. In addition, for example, a mixture of carbon black or activated carbon and a mixture of polyethylene tetrafluoride or polyvinylidene fluoride can be used as the carbon substrate.

The carbon substrate is preferably a porous material such as activated carbon. For example, carbon fiber and pulp subjected to crimping treatment are mixed and dried to form a molded body, and then resin (preferably 10 to 30% by mass of carbon fiber, 40 to 85% by mass of pulp, resin) Porous carbon base material can be obtained by impregnation, and then firing at a temperature of about 400 to 1200 ° C., preferably about 900 ° C. in an inert gas atmosphere.
In the present invention, the porous carbon substrate (hereinafter also referred to as “porous carbon substrate”) has a bulk density of 0.4 to 0.9 g / cm ³ calculated by measuring volume and mass. The carbon base material is meant. Here, the volume is measured using a caliper and a micrometer.

The applying step in the present invention is a step of applying a potential that forms a rectangular wave as described above to the carbon substrate as described above in the above-described electrolytic solution.
The reason why an electric double layer capacitor electrode having a high capacitance can be obtained by the present invention including such an application step is not clear, but the present inventor has determined that the hydroxyl group on the surface of the carbon substrate by the above application step. It is estimated that the capacitance can be increased.

Moreover, in this invention, an electrical double layer capacitor electrode can be manufactured by a normal method using the carbon base material after using the said application process. For example, it can be manufactured by applying a sheet electrode method or a slurry electrode method. Specifically, after subjecting a binder such as polytetrafluoroethylene, polyvinylidene fluoride, and PVA, and a conductive aid such as ketjen black, acetylene black, natural graphite, and artificial black smoke to the application step An electric double layer capacitor electrode can be manufactured by mixing with a carbon substrate. The mixing ratio of the carbon base material subjected to the application step, the binder, and the conductive auxiliary agent is not particularly limited, but is 50 to 95 parts by mass: 1 to 25 parts by mass: 1 to 25 parts by mass. It is preferable.
Further, for example, a carbon sheet having a thickness of 0.5 mm containing, for example, a predetermined amount of polytetrafluoroethylene and a carbon substrate after being subjected to the application step is prepared by a normal calender roll method, and the carbon An electric double layer capacitor electrode can be manufactured by punching out two sheets of, for example, an outer diameter of 16 mm and an area of 2 cm ² and impregnating each sheet with a predetermined electrolyte.

  According to the present invention as described above, it is possible to obtain an electric double layer capacitor electrode having a higher capacitance than the conventional one. Moreover, it can apply also to what formed the carbon raw material of a powder with the binder, and the carbon material which is not powdery, without choosing the shape of the carbon base material used for an electrode.

For example, the following electric double layer capacitor can be produced using the electric double layer capacitor electrode obtained by the present invention as described above.
FIG. 3 is a diagram illustrating a cross-sectional shape of the electric double layer capacitor. In FIG. 3, an electric double layer capacitor 30 includes an electric double layer capacitor electrode 32, a separator 33 that separates the electric double layer capacitor electrode 32 at a central portion, and current collector plates 34 provided at both ends of the electric double layer capacitor electrode 32. And an electrode lead wire 35 connected to the current collector plate 34 and an insulating cell frame 36. More specifically, the electric double layer capacitor 30 is formed by using, for example, a separator 33 made of electronically insulating porous pulp paper having a thickness of 0.3 mm punched to an outer diameter of 17 mm to Composed by separating at the central part.

In addition, there is no restriction | limiting in particular about a collector, A conventionally well-known thing can be used. For example, surface-etched aluminum foil, stainless steel foil, or the like can be used.
Moreover, a separator will not be specifically limited if the requirements, such as chemical resistance and heat resistance which are calculated | required from a manufacturing process and a use, are satisfy | filled. For example, known materials such as polyethylene porous film, polypropylene nonwoven fabric, glass fiber nonwoven fabric, and cellulosic special paper can be used.
The cell shape of the electric double layer capacitor is not particularly limited, and any system such as a coin type, a square type, and a cylindrical type can be adopted.

<Example 1>
A slurry-like composition is obtained by mixing 80% by mass of unbleached kraft pulp (NUKP) with 20% by mass of crimped carbon fiber (trade name: Donakabo S-chop, manufactured by Donac). It was.
Next, the obtained slurry was dehydrated using a paperboard machine and dried at 150 ° C. to obtain a molded body having a thickness of 6 mm. And after impregnating the obtained molded object with a phenol resin (trade name: SP260, manufactured by Asahi Organic Materials Co., Ltd.) at a mass ratio of the molded object: phenolic resin = 100: 80, warm air at 120 ° C. for 20 minutes The resin was cured by drying, and further fired at 900 ° C. in an inert gas atmosphere to obtain a porous carbon substrate.

In the obtained porous carbon base material, pulp and phenol resin were carbonized, and extra components such as tar were removed. Further, the bulk density of the porous carbon substrate was 0.79 g / cm ³ , and the capacitance in 1M sulfuric acid was 3 F / g.
Here, the bulk density of the porous carbon substrate is a value calculated by measuring volume and mass. The volume was measured using a caliper and a micrometer.
In addition, the capacitance is 1M sulfuric acid as an electrolytic solution, a platinum mesh (platinum wire mesh: PT-358055, manufactured by Niraco) capable of accommodating a sample in a pocket is used as a working electrode, and a platinum plate is used as a counter electrode. And a reversible hydrogen electrode were measured by cyclic voltammetry using a three-electrode method in which a potentiostat was connected. In addition, the temperature of the electrolytic solution at the time of measuring the capacitance was 25 ° C., the electrode area was 1 cm ² , and the potential was swept from 0 to 1 V at a potential sweep rate of 1 mV / s with respect to the reversible hydrogen potential. The capacitance was calculated from the current value of 6V.

Next, the obtained porous carbon base material was cut out into a disk shape and placed in a sample pocket provided in a platinum mesh (platinum wire mesh: PT-358055, manufactured by Niraco). Then, as shown in FIG. 2, this was immersed in a phosphoric acid at 170 ° C. placed in a PTFE beaker as a working electrode, and further, a platinum plate as a counter electrode and a reversible hydrogen electrode as a reference electrode were immersed in the working electrode and the counter electrode. And a reference electrode were connected to a potentiostat, and a rectangular wave potential was applied to the porous carbon substrate. Here, the distance between each electrode was adjusted so that the current flowing between the working electrode and the counter electrode did not change.
In this example, as shown in FIG. 1, the upper limit potential of a rectangular wave is +0.7 V, the lower limit potential is +0.1 V, the upper limit potential holding time is 30 seconds, the lower limit potential holding time is 1 second, It was applied until a charge amount of 38,000 C per 1 mol of carbon contained in the carbonaceous substrate flowed. Moreover, it adjusted so that the voltage between the electrode of a porous carbon base material and a counter electrode might become the set upper limit voltage or lower limit voltage using the potentiostat. In the examples, the upper limit potential and the lower limit potential both mean potentials with respect to the reversible hydrogen potential which is a reference electrode.

After flowing a predetermined amount of charge into the porous carbon substrate by such a method, it was taken out from phosphoric acid, and the capacitance in 1M sulfuric acid was measured by the same method as described above. Met. Moreover, the bulk density of the obtained porous carbon base material was 0.70 g / cm ³ . That is, before and after the application of a rectangular wave potential, the decrease in bulk density of the porous carbon substrate was small, and the capacitance was about 19 times.

<Example 2>
In Example 1, it was applied until a charge amount of 38,000 C per 1 mol of carbon contained in the porous carbon base material flowed, but this was applied until a charge amount of 76,000 C flowed, and all other operations were performed. The same experiment as in Example 1 was performed, and the capacitance was measured by the same method. As a result, the capacitance was 146 F / g, and the bulk density of the porous carbon substrate was 0.63 g / cm ³ .

<Comparative Example 1>
A porous carbon substrate having a bulk density of 0.79 g / cm ³ and a capacitance of 3 F / g in 1M sulfuric acid was prepared in the same manner as in Example 1.
Next, CO ₂ gas was allowed to flow at a flow rate of 300 mL / min in an electric furnace whose inside was adjusted to 850 ° C., and the porous carbon base material was put therein and held for 5 hours for activation.
And when the electrostatic capacitance in 1M sulfuric acid was measured by the method similar to the above, it was 21 F / g, and the bulk density of the porous carbon base material was 0.71 g / cm < ³ >.

<Comparative example 2>
In Comparative Example 1, activation was carried out by holding for 5 hours, but this was set to 10 hours, and all other than that, the same experiment as in Comparative Example 1 was performed, and the capacitance was measured by the same method. As a result, the electrostatic capacity was 48 F / g, and the bulk density of the porous carbon substrate was 0.63 g / cm ³ .

<Comparative Example 3>
In Comparative Example 1, activation was carried out by holding for 5 hours, but this was set to 15 hours, and all other experiments were performed in the same manner as in Comparative Example 1, and the capacitance was measured by the same method. As a result, the electrostatic capacity was 78 F / g, and the bulk density of the porous carbon substrate was 0.55 g / cm ³ .

FIG. 4 shows the relationship between the bulk density of the porous carbon substrate and the capacitance in the case of Example 1, Example 2, Comparative Example 1, Comparative Example 2, and Comparative Example 3 described above. Moreover, in FIG. 4, the plot which shows the relationship between the bulk density in the porous carbon base material before activation and an electrostatic capacitance is shown.
In contrast to Comparative Examples 1 to 3 activated using CO ₂ gas, it can be seen that in Examples 1 and 2, the capacitance with respect to the bulk density of the porous carbon substrate is increased.

<Example 3>
In Example 1, the lower limit potential of the rectangular wave was fixed at +0.1 V, but this was changed to 0.0, +0.2 V, +0.3 V, +0.4 V, +0.5 V, and +0.6 V. In each case, the same experiment as in Example 1 was performed, and the capacitance was measured by the same method. The results are shown in FIG. 5 together with the case of Example 1. In FIG. 5, the electrostatic capacity is shown as a ratio (capacitance after processing / original electrostatic capacity) before and after applying a rectangular wave potential.
As shown in FIG. 5, it was found that the electrostatic capacity increased when the lower limit potential was 0.0 to +0.3 V, and the electrostatic capacity was particularly increased when the lower limit potential was 0.0 to +0.1 V.

<Example 4>
In Example 1, the upper limit potential of the potential forming the rectangular wave was fixed to + 0.7V, but this was changed to + 0.4V, + 0.5V, + 0.6V, + 0.8V, + 0.9V, + 1.0V. In each case, the same experiment as in Example 4 was performed, and the capacitance was measured by the same method. The results are shown in FIG. 5 together with the case of Example 1. In FIG. 5, the electrostatic capacity is shown as a ratio (capacitance after processing / original electrostatic capacity) before and after applying a rectangular wave potential.
As shown in FIG. 5, it was found that the capacitance increases when the lower limit potential is +0.5 to +0.7 V.

<Example 5>
In the same manner as in Example 1, preparation was made to apply a rectangular wave potential to the porous carbon substrate. And the change of the charge amount (integrated charge amount increase rate per unit time) of the porous carbon base material after switching from +0.1 V that is the lower limit potential to +0.7 V that is the upper limit potential was measured. The measurement results are shown in FIG. In addition, the charge amount of the porous carbon substrate was measured by chronocoulometry (a method for measuring the charge when a constant potential was applied).
From FIG. 6, it can be seen that the change rate of the accumulated charge amount per unit time becomes extremely small after 60 seconds after switching from the lower limit potential to the upper limit potential. Moreover, it can be said that the upper limit potential holding time is desirably about 10 to 30 seconds.

<Example 6>
In Example 1, it was applied until a charge amount of 38,000 C per 1 mol of carbon contained in the porous carbon substrate flowed. This was applied to 1,000 C, 10,000 C, 38,000 C, 50,000 C, 70, In each case where the charge was changed to flow until 000 C and 100,000 C charge flows, the same experiment as in Example 1 was performed, and the bulk density was measured by the same method. The results are shown in FIG. In FIG. 7, the bulk density is shown as a ratio before and after applying a rectangular wave potential (bulk density after treatment / original bulk density (0.70 g / cm ³ )).
As shown in FIG. 7, it can be seen that a bulk density of about 70% of the original bulk density is maintained even when a charge amount of 120,000 C is passed. Therefore, it can be said that the electrode of the present invention is not easily destroyed and is easy to handle.

5 Container 15 Electrolyte 10 Carbon Base Material 20 Working Electrode 22 Counter Electrode 24 Reversible Hydrogen Electrode 26 Potentio Stud 30 Electric Double Layer Capacitor 32 Electric Double Layer Capacitor Electrode 33 Separator 34 Current Collector Plate 35 Lead Wire 36 Insulated Cell Frame

Claims (9)

  A method for producing an electric double layer capacitor electrode, comprising a step of applying a potential that forms a rectangular wave to a carbon substrate in an electrolytic solution.   The method for producing an electric double layer capacitor electrode according to claim 1, wherein the voltage is applied to the carbon substrate in the electrolytic solution at 150 to 220 ° C.   The method for producing an electric double layer capacitor electrode according to claim 1, wherein the electrolytic solution is phosphoric acid or sulfuric acid.   The method for producing an electric double layer capacitor electrode according to any one of claims 1 to 3, wherein a lower limit potential of the potential forming the rectangular wave is 0.0 to +0.3 V with respect to a reversible hydrogen electrode used as a reference electrode. .   The method for producing an electric double layer capacitor electrode according to any one of claims 1 to 4, wherein an upper limit potential of the potential forming the rectangular wave is +0.5 to +0.7 V with respect to a reversible hydrogen electrode used as a reference electrode. .   The method for producing a potential double layer capacitor electrode according to any one of claims 1 to 5, wherein the charge is applied until a charge amount of 3,800 to 120,000 C flows per mol of carbon contained in the carbon substrate.   The manufacturing method of the electric double layer capacitor electrode according to any one of claims 1 to 6, wherein a holding time of the upper limit potential of the potential forming the rectangular wave is 10 to 60 seconds.   The electric double layer capacitor electrode obtained by the manufacturing method of the electric double layer capacitor electrode in any one of Claims 1-7.   An electric double layer capacitor comprising the electric double layer capacitor electrode according to claim 8.

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