JP2016111222A - Electric double layer capacitor and electrode material and method of producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrode material capable of increasing the specific capacity compared with active carbon and a production method thereof, and to provide a polarizable electrode of good conductivity, and an electric double layer capacitor using that electrode.SOLUTION: In a method of producing an electrode material, a carbon nanoballoon structure is formed by heat treating carbon black at a temperature of 2000°C or more, and it is furthermore activated by alkali activation. An electrode is manufactured of the activated material, and an electric double layer capacitor using it as a polarizable electrode is manufactured.SELECTED DRAWING: Figure 7

Description

  The present invention relates to an electrode material used for a polarizable electrode of an electric double layer capacitor, a manufacturing method thereof, and an electric double layer capacitor using a polarizable electrode made of the electrode material.

  In recent years, as represented by hybrid vehicles, energy-saving technologies for regenerating energy have been developed. This regenerates kinetic energy (braking energy) as electrical energy and stores it, but it is deteriorated when a secondary battery or the like repeatedly charges and discharges a large current because charging and discharging a large current is repeated. Could be the cause of progress. In view of this, a method of causing such a load to be borne by a capacitor has been devised, and an electric double layer capacitor is drawing attention as the capacitor.

  As is well known, an electric double layer capacitor is one in which an electric double layer is formed at the interface between an electrolyte and an electrode by applying a voltage to a polarizable electrode sandwiching a dielectric. Compared with a secondary battery, the electric double layer capacitor does not cause an oxidation-reduction reaction, and therefore has advantages such as being able to charge and discharge even at a large current and having a long life. In particular, a regenerative brake that regenerates braking energy as electric energy is performed by a capacitor, so that the number of times of charging / discharging of the battery can be reduced.

  As a polarizable electrode of this type of electric double layer capacitor, there is one obtained by mixing activated carbon with conductive carbon black (Patent Document 1). In this technology, activated carbon having a large specific surface area is used as an electrode material in consideration of the adsorption performance of electrolyte ions (specific capacity, that is, electrostatic capacity as a capacitor). However, since the resistance of activated carbon is large, it functions as a conductive agent. The conductive carbon black was mixed.

  However, in order to reduce the resistance of the polarizable electrode, if the mixing ratio of the conductive carbon black is increased, the amount of activated carbon is reduced, and the specific capacity (capacitance) is reduced. . Therefore, in place of the conductive carbon black, Ketjen Black (registered trademark) or furnace black (carbon black produced by the furnace method), which is one of conductive carbons, is used. It has been proposed to reduce the compounding rate of the agent (Patent Document 2).

  However, since the ketjen black (registered trademark) and furnace black are for functioning as a conductive agent, it is essential to mix activated carbon with a large specific surface area, and function as the main material of the polarizable electrode. It wasn't something to do. Therefore, the specific capacity (capacitance) has to rely exclusively on the specific surface area of the activated carbon, and it has not been possible to dramatically improve conduction and specific capacity.

  Therefore, it has been proposed to use carbon nanotubes as a polarizable electrode structure that does not use activated carbon (Patent Document 3). This technique is to grow carbon nanotubes on the surface of the catalytic metal layer laminated on the substrate by the CVD method. The carbon nanotube can function as a polarizable electrode, and at the same time, the substrate can function as a current collector. That's it. However, it has been reported that the capacitance of the electric double layer capacitor using the substrate manufactured by the above method can be stably charged and discharged, but the capacitance is only as high as that of activated carbon. Thus, an electrode more efficient than activated carbon could not be obtained.

  On the other hand, the inventors of the present application have developed that carbon nanoballoon structures can be formed by heating at high temperature in an inert gas atmosphere against soot generated by arc discharge (hereinafter referred to as arc black). (Patent Document 4). The carbon nanoballoon structure produced here is arranged so that the graphite layer (graphite layer) forms a curved surface, and has a hollow structure (balloon) such as a spherical shape or a gourd shape as a whole or in part. there were. Further, when the ketjen black (registered trademark) is also heat-treated, it is possible to obtain a carbon nanoballoon structure having several to 14 to 14 graphite layers, a diameter of 30 to 50 nm, and a porosity of 40 to 75%. It was also found out. However, since the carbon nanoballoon structure produced by the above technique has a hollow structure, it is expected to be a light absorbing material, a superhard material, a hydrogen storage body, etc. No use has been found.

  In addition, it has been proposed that porous fibrous nanocarbon in which radial pores are formed in the fiber axis direction from the outer peripheral surface of the nanofiber can be used as an adsorbent, a chromatographic substance, a catalyst carrier, and the like (Patent Document 5). ). Although this technology is characterized by high porosity and uniform size, it has been unclear whether it can be used for electric double-layer capacitors because it has not been analyzed for resistance and specific surface area. there were.

JP-A 63-244839 JP-A-7-320986 Japanese Patent Laid-Open No. 2004-289421 JP 2005-281055 A JP 2008-526663 A

Y.Okabe, H.Izumi, Y.Suda, H.Tanoue, H.Takikawa, H.Ue, K.Shimizu “Improvement in the Characteristic of Electric Double Layer Capacitor by Using the Mixture of Arc-Black and Carbon Nanoballoon” JPN J. Appl. Phys., 52 (2013) 11NM05 Y.Okabe, Y.Suda, H.Tanoue, H.Takikawa, H.Ue, K.Shimizu “Improving the characteristic of electric double layer capacitors using oxidized carbon nanoballoon” Electrochimica Acta, 131 (2014) 207-213

  As described above, the structure of the conventional electric double layer capacitor is to secure the capacitance by the specific surface area of the activated carbon or to use the specific surface area due to the structural characteristics of the carbon nanotube. It was not a dramatic improvement.

  Therefore, the present inventors compared the electric characteristics such as conductivity (internal resistance) of the arc black and the carbon nanoballoon structure with activated carbon, and found that the conductivity of the carbon nanoballoon structure is a precursor. Discovered that it is superior to black (see Non-Patent Document 1), and further analyzed the electrical characteristics of the oxidized carbon nanoballoon structure obtained by oxidizing the carbon nanoballoon structure (see Non-Patent Document 2) . From these studies, we found the possibility of using as a polarizable electrode for electric double layer capacitors from the specific capacity of carbon nanoballoon structures using arc black. However, in comparison with activated carbon, even if the conductivity is sufficiently high, the specific capacity has not been dramatically increased.

  The present invention has been made in view of the above-mentioned points, and an object of the present invention is to provide an electrode material capable of increasing the specific capacity as compared with activated carbon, and a method for producing the same, and at the same time, conductive. And providing an electric double layer capacitor using the electrode.

  The present inventors have studied whether the specific surface area can be increased by further processing the carbon nanoballoon structure. As a result of specific treatment, the specific capacity increases and the internal resistance decreases. The present invention has been found and the present invention has been completed.

The Ketjen Black (registered trademark) is a kind of carbon black and has high conductivity, and is therefore used as a conductivity improving material for electric double layer capacitors. However, the ketjen black (registered trademark) itself was not used as an electrode material.
An electric double layer capacitor utilizing the high specific surface area of activated carbon has been put into practical use by adding the ketjen black (registered trademark) to the activated carbon.
On the other hand, the present inventors have found that an electrode of an electric double layer capacitor having a high conductivity can be obtained by using only a material obtained by heat-treating the ketjen black (registered trademark).

  That is, the present invention relating to a method for producing an electrode material is a method for producing a material for an electrode used in an electric double layer capacitor, wherein the carbon nanoballoon structure is obtained by heat-treating carbon black at a temperature of 2000 ° C. or higher. And is further activated by an alkali activation method.

  According to the above configuration, a part of the hollow structure formed in the carbon nanoballoon structure can be opened, and pores can be formed on the surface of the carbon nanoballoon structure and the inner surface of the hollow structure part. The specific surface area as a whole can be increased, and it is suitable for the electrode material used for the electric double layer capacitor.

  In the invention of the above configuration, the carbon black is preferably ketjen black (registered trademark), and the heating temperature in the heat treatment is preferably 2400 ° C. or higher.

  By using the ketjen black (registered trademark) as the carbon black, it is possible to obtain an electrode material that increases the specific surface area while reducing the electrical resistance. Moreover, the carbon nanoballoon structure by the said ketjen black (trademark) can be obtained by heating temperature to 2400 degreeC or more. In addition, although the upper limit of heating temperature is assumed to be 3000 degreeC, if it is 2800 degrees C or less, a suitable carbon nanoballoon structure can be obtained.

  Moreover, it is preferable that the activation process in the invention of each configuration uses an aqueous potassium hydroxide solution adjusted to a molar concentration of 1 mol / L or more and 7 mol / L or less.

  The activation treatment is based on the alkali activation method. When the alkaline aqueous solution to be used is potassium hydroxide, if the molar concentration is too large, the degree of opening is too large for the hollow structure of the carbon nanoballoon structure. There is a possibility that the hollow structure is no longer maintained. Therefore, the hollow structure portion of the carbon nanoballoon structure can be appropriately opened by using a relatively low concentration alkaline aqueous solution. In addition, if it is in the range of 1 mol / L-7 mol / L, a specific capacity can be increased rather than the state before activation, but the molar concentration of 5 mol / L is preferable and the molar concentration of 3 mol / L is more. Is preferred.

  The present invention relating to an electrode material is an electrode material produced by any of the inventions relating to the production method, wherein a part of each hollow structure part forming the carbon nanoballoon structure is opened, The carbon nanoballoon structure has a structure in which pores are formed on each of the outer surface and the inner surface of the hollow structure portion.

  According to the above configuration, a part of each hollow structure part formed in the carbon nanoballoon structure is open, so that the inside of the hollow structure part becomes a part of the surface. Since pores are formed on the surface of the body and the inner surface of the hollow structure portion, the overall structure is porous, so that the specific surface area can be increased. The specific capacity can be increased by increasing the specific surface area. In addition, the graphite structure will decrease, and this seems to be a factor, but the internal resistance increases and the conductivity decreases, but the increase in specific surface area due to the porous structure as described above, A specific capacity sufficient to compensate for the decrease in conductivity can be obtained.

  The present invention relating to an electric double layer capacitor uses the electrode material described above, and is characterized by comprising a polarizable electrode made of the electrode material.

  According to the above configuration, in the electric double layer formed at the boundary between the polarizable electrode and the electrolytic solution, ions that can be adsorbed are increased, whereby an electric double layer capacitor having a large capacitance can be obtained. It is.

According to the present invention relating to the method for producing an electrode material, an electrode having a large specific capacity can be obtained. And since it is based on an alkali activation method after heat processing, it can manufacture without passing through a complicated manufacturing process. Further, according to the present invention relating to the electrode material, since the specific surface area is remarkably large, the internal resistance is increased, but the specific capacity is increased as the specific surface area is increased to compensate for the increase in the electric capacity. It can be used as a polarizable electrode of a double layer capacitor. Furthermore, according to the electric double layer capacitor of the present invention, even when compared with activated carbon, it is possible to obtain an effect of having a larger capacitance, charge / discharge of a large current is possible, and regenerative energy in an automobile is assumed. Thus, high-speed charging / discharging is possible.

It is a figure which shows the activation process condition dependence of the weight loss in dry air at the time of performing the thermogravimetric analysis of a carbon nanoballoon structure. It is a graph which shows the relationship between the voltage scanning speed computed from cyclic voltammetry measurement, and a specific capacity. It is the Ragon plot calculated | required from the cyclic voltammetry measurement. It is a graph which shows the relationship between the current density computed from constant current charge / discharge measurement, and a specific capacity. It is a Ragon plot calculated | required from the constant current charging / discharging measurement. It is a schematic diagram at the time of using the material in which the carbon nanoballoon structure was formed as an electrode. It is a schematic diagram at the time of using as the electrode the material which performed the activation process after forming the carbon nanoballoon structure.

  Details of the present invention will be described together with embodiments. First, a method for manufacturing an electrode material will be described. As a manufacturing method of an electrode material, a carbon nanoballoon structure is formed by heat-treating carbon black, and then an activation treatment is performed by an alkali activation method. As the carbon black, in addition to the aforementioned arc black, acetylene black (carbon black produced by the acetylene method), furnace black, ketjen black (registered trademark), and the like can be used. Although the temperature setting during the heat treatment varies depending on the type of carbon black used, a hollow structure can be formed in the carbon black at a heating temperature of 2000 ° C. or higher. However, if the heating temperature is increased, the number of layers of the graphite structure is increased and the thickness is increased. Therefore, the range of 2000 ° C. to 2800 ° C. is estimated as an appropriate heating temperature.

  Therefore, in this embodiment, Ketjen Black (registered trademark) is used and heat treatment at 2400 ° C. is performed. The heating temperature is set higher than that of Arc Black. This is due to the state of the carbon particles forming the carbon black. The difference is that the arc black is a spherical fine particle in which an amorphous component having a particle size of about 50 nm is dominant, whereas the Ketjen Black (registered trademark) is a spherical fine particle in which an amorphous component having a particle size of about 30 nm is dominant. There is. The heat treatment was performed in an argon gas atmosphere. A suitable carbon nanoballoon structure made of the ketjen black (registered trademark) can be obtained under the above heating conditions.

  The activation process is performed on the carbon nanoballoon structure thus manufactured. The activation treatment is based on an alkali activation method, and specifically uses an aqueous potassium hydroxide solution. Since 1.2 g of carbon nanoballoon structure (powder) is added to 200 mL of an appropriate concentration potassium hydroxide aqueous solution and stirred at 60 rpm for 30 minutes, an alkaline solution acts on the carbon nanoballoon structure. is there. After that, it was filtered and dried. Further, the activation treatment is completed by heating in a heating furnace set at 800 ° C. for 1 hour, neutralizing with dilute hydrochloric acid, further filtering and washing, and drying with a vacuum dryer.

  Here, depending on the concentration of the alkaline solution used for the activation treatment, the degree of opening becomes large with respect to the hollow structure of the carbon nanoballoon structure, which may cause a state in which the hollow structure is not maintained. The proper concentration (molar concentration) when used is in the range of 1 mol / L to 7 mol / L. Although the condition of changing the mixing and stirring time is also conceivable, the concentration condition is set in order to perform the activation process more stably than the stirring time.

  In the carbon nanoballoon structure activated by the process as described above, pores were formed on the surface of the carbon nanoballoon structure and the inner surface of the hollow structure in addition to a state in which a part of the hollow structure was opened. Since the structure is assumed to be porous as a whole, the structure has a large surface area including the surface of the structure and the inner surface of the hollow structure. This is the electrode material.

  Therefore, a polarizable electrode is produced using this electrode material. There is a method of forming an electrode into a desired shape using a binder. For example, 90 mg of the electrode material is added with 10 mL of a polytetrafluoroethylene (PTFE) dispersion (containing 10 mg of PTFE) as a binder, and kneaded for about 15 minutes. It is put into a mold and pressed at room temperature under a pressure of 14 MPa for about 10 minutes. In addition, the electrode produced in this way can provide an electric double layer capacitor with a large electrostatic capacity by providing it as a polarizable electrode on both sides of the separator.

  Below, the content of the experiment conducted in order to confirm the effect of this invention is demonstrated.

<Production of carbon nanoballoon structure>
For comparison with Ketjen Black (registered trademark), which is a precursor of the carbon nanoballoon structure described in this example, a carbon nanoballoon structure using Arc Black as a precursor, and the Ketjen Black (registered trademark) ) Was used as a precursor. The arc black was synthesized using a twin torch arc apparatus. The twin torch arc device has a structure in which two arc torch-like graphite electrodes facing each other at almost right angles (for example, facing each other at 80 degrees) are installed in the chamber, and the evaporation electrode and the counter electrode have different diameters. G347S (φ6 mm × 150 mm) manufactured by Tokai Carbon Co., Ltd. was used as the evaporation electrode, and G348 (φ10 mm × 150 mm) manufactured by Tokai Carbon Co., Ltd. was used as the counter electrode. Arc black was synthesized under the conditions of a nitrogen gas flow rate of 20 L / min, a pressure in the chamber of 80 kPa, and an arc current of AC 200A.

  For the production of the carbon nanoballoon structure, the arc black was heat-treated at a temperature of 2000 ° C., and the ketjen black (registered trademark) was heat-treated at a temperature of 2400 ° C. The heat treatment was performed in an inert gas atmosphere.

<Activation processing>
A potassium hydroxide aqueous solution was used for the activation treatment. In order to obtain an appropriate concentration, three types of aqueous potassium hydroxide solutions having different molar concentrations were prepared, and an activation treatment was performed on the carbon nanoballoon structure having the ketjen black (registered trademark) as a precursor. Three types of potassium hydroxide aqueous solution were 3 mol / L, 5 mol / L, and 7 mol / L. In the activation treatment, 200 mL of each of these three types of potassium hydroxide aqueous solutions was used, 1.2 g of the carbon nanoballoon structure was added thereto, and the mixture was stirred at 60 rpm for 30 minutes.

  Then, it filtered and it dried at 100 degreeC for 1 hour using the vacuum dryer. Subsequently, carbonization was performed by heating in a heating furnace at 800 ° C. for 1 hour at a flow rate of nitrogen gas of 80 mL / min. At this time, the heating conditions by the vacuum dryer were 1 hour for the temperature rise from room temperature to 800 ° C., 1 hour while maintaining the temperature at 800 ° C., and then cooled to room temperature by natural cooling. The material collected after drying was neutralized by ultrasonic dispersion using 200 mL of dilute hydrochloric acid having a concentration of 2 mol / L. Then, it filtered and wash | cleaned with distilled water 500mL. For washing, a method of stirring for 15 minutes with an ultrasonic homogenizer was adopted. Finally, it was filtered and dried in a vacuum dryer at 100 ° C. for 1 hour.

  For convenience of explanation, the material produced as described above is represented by the following symbols. A material made of the carbon nanoballoon structure having the arc black as a precursor is referred to as CNB, and a material having the carbon nanoballoon structure having the ketjen black (registered trademark) as a precursor is referred to as CNB-CB. Moreover, the material which performed the activation process is called ACNB-CB, and depending on the density | concentration (3 mol / L, 5 mol / L, 7 mol / L) of the potassium hydroxide aqueous solution used in the activation process, -KOH3M at the end, -KOH5M and -KOH7M are used for distinction.

<Thermogravimetric analysis>
The produced carbon nanoballoon structure was analyzed using thermogravimetric analysis (TGA). Thermogravimetric analysis measures the change in weight when the temperature is raised. FIG. 1 shows the temperature dependence of weight loss in dry air. Although the carbon nanoballoon structure disappears due to the oxidation, it is considered that the higher the oxidation temperature, the more the graphite structure. By heat-treating the ketjen black (registered trademark), CNB-CB contains a lot of graphite structure, and the conductivity is improved. Moreover, it is thought that by performing the activation treatment, the hollow structure was broken and the oxidation temperature was lowered.

<Raman spectroscopy>
The crystallinity of the produced carbon nanoballoon structure was analyzed using Raman spectroscopy. Table 1 shows the results of measuring the G / D ratio. Here, the G / D ratio is a Raman scattering intensity ratio, the G band is a peak derived from a carbon graphite structure, and the D band is a peak derived from a defect in the carbon graphite structure.

  A higher G / D ratio indicates more graphite structure and higher crystallinity. According to this analysis result, at the stage where CNB-CB was produced from ketjen black (registered trademark), many graphite structures were included. On the other hand, it shows that the graphite structure is broken because the G / D ratio is lowered by performing the activation treatment. Although the G / D ratio varies depending on the KOH concentration during the activation treatment, ACNB-CB-KOH3M has the lowest G / D ratio, so this condition is considered optimal.

<Production of electrode>
Electrodes were prepared using five types of materials, CNB, CNB-CB, ACNB-CB-KOH3M, ACNB-CB-KOH5M, and ACNB-CB-KOH7M prepared as described above. The electrode was prepared by preparing 90 mg of each of the above materials, using 10 μL of PTFE dispersion (containing 10 mg of PTFE) as a binder, kneading both for 15 minutes, and then dividing the material by 50 mg, The mold was placed and pressed at room temperature under a pressure of 14 MPa for 10 minutes. The electrode shape was a coin type and could be used as a polarizable electrode.

<Production of electric double layer capacitor>
An electric double layer capacitor was produced by using two coin-type electrodes produced as described above. To manufacture the electric double layer capacitor, an electrode cell manufactured by Toyo System Co., Ltd. was used, and assembly was performed in a probe box filled with nitrogen gas. For the production, the first collector electrode, the first coin-type polarizable electrode, the separator, the second coin-type polarizable electrode, and the second collector electrode are placed in the electrode cell in the order of electrolysis. As a liquid, 1 mol / L TEMABF ₄ / PC which is an organic electrolyte was injected and sealed. As the collector electrode, SUS mesh 316-200 mesh manufactured by Niraco Co., Ltd. was used, and TF4030 manufactured by Nippon Advanced Paper Industries Co., Ltd. was used as the separator.

<Experimental conditions and experimental results>
About five types of electric double layer capacitors produced by the above, the electrochemical measurement was performed with the electrochemical measurement system HZ-5000 by Hokuto Denko. Measurement was performed by cyclic voltammetry (CV) measurement and electrochemical impedance measurement.

  In the CV measurement, the potential window was set to 0 V to 2.5 V, and the voltage scanning speed was measured at 1 mV / s and 100 mV / s. In addition, when calculating | requiring the capacity | capacitance (C) of charging / discharging by CV measurement, the following formula was used.

ただし、
Ｉ ：電流［Ａ］
Ｖ ：電圧［Ｖ］
ΔＶ：電圧走査速度［Ｖ／ｓ］
ｍ ：電極１枚分のカーボンナノ材料の質量［ｇ］

However,
I: Current [A]
V: Voltage [V]
ΔV: Voltage scanning speed [V / s]
m: mass of carbon nanomaterial for one electrode [g]

  In the constant current charge / discharge measurement, the current density was changed from 0.1 A / g to 2.0 A / g. In addition, based on the measurement result, the specific capacity (C), output density (P), and energy density (E) of the capacitor were calculated by the following equations.

ただし、
Ｉ ：電流［Ａ］
Ｖ_１ ：満充電電圧の８０％［Ｖ］
Ｖ_２ ：満充電電圧の４０％［Ｖ］
ｔ_１，ｔ_２ ：Ｖ１，Ｖ２のときの時間［ｓ］
Ｖ ：電位窓［Ｖ］
（Ｔ２−Ｔ１） ：放電時間［ｓ］
ｍ ：電極２枚分のカーボン材料の質量［ｇ］

However,
I: Current [A]
V ₁ : 80% of full charge voltage [V]
V ₂ : 40% of full charge voltage [V]
t ₁ , t ₂ : time [s] when V1 and V2
V: Potential window [V]
(T2-T1): Discharge time [s]
m: mass of carbon material for two electrodes [g]

  FIG. 2 shows the result of specific capacity based on the voltage scanning speed obtained by CV measurement and the Ragon plot, and FIG. 3 shows the result of specific capacity at each current density obtained by constant current charge / discharge measurement. Shown in In FIG. 3, activated carbon (referred to as AC) is displayed as a comparison target.

  As is clear from FIG. 2, the specific capacity calculated from the CV measurement is larger for CNB-CB than for CNB, and further, for ACNB-CB-KOH subjected to activation treatment, greater than for CNB-CB. Yes. In particular, when compared with a scan rate of 100 (mV / s), the specific capacity of CNB is about 32 (F / g), and considering that activated carbon is about 20 (F / g), about 1. If it is a numerical value of 6 times and CNB-CB is used, it will be about 37 (F / g), and will be about 1.2 times of CNB (about 1.85 times of activated carbon). Furthermore, in the case of ACNB-CB-KOH3M, which resulted in the largest specific capacity, it was about 54 (F / g), so that the specific capacity was about 2.7 times that of activated carbon. Thereby, it turns out that the electrostatic capacitance of an electric double layer capacitor can be increased dramatically.

  Further, as is apparent from FIG. 3, the value of the energy density with respect to the output density is increased, and it can be seen that high-speed charging / discharging is possible while having a large capacity.

  Furthermore, as is clear from FIG. 4, a large specific capacity can be obtained in charge / discharge in a range where the current density is large as compared with the case of activated carbon (AC). In particular, as represented by ACNB-CB-KOH3M, in the case of a material that has been subjected to an activation treatment, it can be seen that a larger specific capacity can be obtained than a material that is not subjected to an activation treatment.

  According to the Ragon plot shown in FIG. 5, it was found that the output density was stable while maintaining the energy density in comparison with activated carbon (AC), and charge and discharge were possible at high speed while having a large capacity.

  The above results indicate that not only a part of the hollow part formed in the carbon nanoballoon structure is opened, but also pores are formed on the surface of the carbon nanoballoon structure and the inner surface of the hollow structure. FIG. 6 shows a schematic diagram of the state. FIG. 6 shows the state of the electrode by CNB-CB which is not activated, and FIG. 7 shows the state of the electrode of ACNB-CB which has been activated. In the figure, the black part is an electrode, and the gray part is an electrolyte. As shown in this figure, CNB-CB (see FIG. 6) has unevenness due to the carbon nanoballoons on the surface, and the overall specific surface area is large. Even in this state, since the specific surface area is reasonably large, it is considered that the specific capacity can be increased. On the other hand, in the activated ACNB-CB (see FIG. 7), the electrolyte penetrates into the carbon nanoballoon, and a larger specific surface area is obtained by the combined portion of the inner surfaces of the carbon nanoballoon. Is.

  As described above, the embodiments and examples of the present invention have been described. However, these are merely examples of the present invention, and the present invention is not limited thereto. Accordingly, it is possible to appropriately change the configuration of the embodiment. For example, the embodiment using ketjen black (registered trademark) as the carbon black has been mainly described, but other carbon blacks can also be used. In this case, the temperature of the heat treatment and the concentration of the alkali solution used for the activation treatment are appropriately adjusted.

The electric double layer capacitor using the polarizable electrode of the electrode material of the present invention can be used for an auxiliary power supply circuit and a regenerative power storage circuit used in a vehicle such as a hybrid vehicle or an electric vehicle, as well as an integrated circuit. It can also be used for backup power supplies, uninterruptible power supplies, and smart meters. It can also be used for medical equipment such as an X-ray imaging system. In addition, it can also be used in distributed power generation devices (energy buffers such as solar power generation) and power storage facilities (storage of surplus power).

Claims (5)

A method for producing a material for an electrode used in an electric double layer capacitor, comprising:
A method for producing an electrode material, comprising: forming a carbon nanoballoon structure by heat treatment of carbon black at a temperature of 2000 ° C. or higher, and further performing an activation treatment by an alkali activation method.   The method for producing an electrode material according to claim 1, wherein the carbon black is Ketjen Black (registered trademark), and a heating temperature in the heat treatment is 2400 ° C or higher.   The method for producing an electrode material according to claim 1 or 2, wherein the activation treatment uses a potassium hydroxide aqueous solution adjusted to a molar concentration of 1 mol / L or more and 7 mol / L or less.   An electrode material manufactured by the manufacturing method according to claim 1, wherein a part of each hollow structure part forming the carbon nanoballoon structure is opened, and the carbon nanoballoon structure is formed. An electrode material having a structure in which pores are formed on each of an outer surface of a body and an inner surface of the hollow structure portion. It is an electrical double layer capacitor using the electrode material of Claim 4, Comprising: The polarizable electrode produced with the said electrode material is provided, The electrical double layer capacitor characterized by the above-mentioned.

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