JPH10242010A - Manufacture of active carbon electrode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To sufficiently disperse excessive thermosetting resin by compulsorily discharging the decomposition gas of thermosetting resin in the course of heat treatment. SOLUTION: In the course of heat treatment, the decomposition gas or the like of phenolic resin which has been generated in a furnace is compulsorily discharged outside the furnace, by vacuum discharge in an exhaust process 5, and the atmospheric pressure in the furnace is maintained to be almost constant. That is, the decomposition gas of phenolic resin is prevented from remaining in the vicinity of the surface of a molded object, and decomposition is accelerated. A part of phenolic resin is carbonized and excessive parts are sufficiently dispersed to form active carbon-carbon compound material with a specified sinter density and deflection strength. Thereby an electric double layer capacitor having large capacitance and low capacity reduction ratio can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an activated carbon electrode, and more particularly to an improvement in a heat treatment process.

[0002]

2. Description of the Related Art For example, electric double layer capacitors are widely used as memory backup components. The electric double layer capacitor utilizes the fact that a pair of charge layers (that is, an electric double layer) having different signs are formed at the interface between the conductor forming the pair of electrodes and the electrolyte solution, and can be rapidly charged. In addition, there is a characteristic that the life cannot be deteriorated due to charging and discharging. Therefore, for example, an electric double-layer capacitor is connected in parallel with a battery or a commercial AC power supply that is converted to DC, and various components are backed up by the electric charge stored in the electric double-layer capacitor when the power supply is momentarily interrupted. Used in In recent years, by making such an electric double-layer capacitor capable of discharging a large capacity and a large current, it is considered that the electric double-layer capacitor is used for, for example, a regenerative energy storage device of an electric vehicle, a cell motor drive of the vehicle, a solar cell voltage leveling, and the like. Have been.

Conventionally, activated carbon powder, activated carbon fiber and the like have been used as the electrodes of the electric double layer capacitor as described above. Since the capacitance of the electric double layer capacitor is determined by the amount of electric charge stored in the electric double layer, a larger capacitance can be obtained as the surface area of the electrode is larger, so that the electric double layer capacitor has high conductivity and specific surface area. Activated carbon is suitable as an electrode material. However, since activated carbon is generally in the form of powder or fiber, when it is used as an electrode, electrical contact between the powder or fiber is ensured by, for example, storing it in a metal case or the like and applying pressure. Therefore, in order to obtain a large capacitance, it is necessary to increase the surface area by increasing the amount of activated carbon and to increase the pressing force in order to further ensure the electrical contact of the activated carbon. Extremely large. For this reason, an electric double-layer capacitor of a practical size can obtain only a capacitance of about several F at most, and there is a problem that the application for memory backup as described above is limited.

[0004]

Therefore, there has been proposed a solid activated carbon electrode in which activated carbon powder is solidified using a thermosetting resin while maintaining a high specific surface area. For example, a solid activated carbon electrode (hereinafter, referred to as a solid activated carbon electrode) constituting an electrode of a large-capacity electric double layer capacitor described in Japanese Patent Publication No. 7-91449 or the like. According to such a solid activated carbon electrode, electrical contact between activated carbon powders can be obtained without particularly applying pressure, so that the capacitance and discharge current value can be increased while keeping the dimensions of the electric double layer capacitor relatively small. .

[0005] Incidentally, the above-mentioned solid activated carbon electrode is prepared by mixing a thermosetting resin with activated carbon powder to form a desired shape, and then, for example, in a non-oxidizing atmosphere in which the gas in the furnace is replaced with nitrogen gas, at a predetermined temperature. It is manufactured by carbonizing the thermosetting resin by heat treatment. As a result, the activated carbon powder is bonded to each other by the carbide of the thermosetting resin without significantly reducing its specific surface area, and electrical contact between the activated carbon powders is secured while maintaining the large specific surface area. . Moreover, since the activated carbon powder is firmly bound by the carbide, the solid activated carbon electrode is given high mechanical strength and high conductivity.

However, when an electric double layer capacitor is manufactured using the solid activated carbon electrode obtained by the above-described manufacturing method, the expected high capacitance cannot be obtained and the capacity reduction rate is large. For example,
It became clear that application to regenerative energy storage devices and the like that require rapid charge and discharge is difficult. Note that the volume reduction factor, the percentage of reduction of the electrostatic capacitance C ₂ at the time of large current charging and discharging of the capacitances C ₁ at the time of a small current charge and discharge ([C ₂ -C
₁ ] / C ₁ ). Usually, the electric double layer capacitor has a small amount of electric current with a small current of about several hundreds (mA), which has a small effect on the mobility of ions, for example, a value standardized by the area of a pair of activated carbon electrodes facing each other. On the other hand, in actual use, the battery is charged and discharged with a large current of several hundred times or more of the measured current. Therefore, it is desired that the capacity reduction rate of the electric double layer capacitor be as small as possible.

The cause of the above problem is considered as follows. That is, since the carbide derived from the thermosetting resin has a small specific surface area, it hardly contributes to the accumulation of electric charge, and forms macropores which function exclusively as a passage for electrolyte ions leading to the activated carbon surface. On the other hand, when the activated carbon powder is formed into a desired shape in the above-described production process, it is necessary to add a larger amount of thermosetting resin than an amount corresponding to the amount of carbide necessary for obtaining mechanical strength. Therefore, the amount of carbide remaining in the solid activated carbon electrode after the heat treatment becomes excessive, and the macropore is closed by the excess carbide, or the pore diameter is reduced, and the length is further increased. As a result, the migration resistance of the electrolyte ions becomes large, and a large voltage drop occurs at the time of large current discharge, so that the capacitance apparently decreases.
Therefore, the amount of carbide remaining in the solid activated carbon electrode is
It is desired that the amount is as small as possible within a range where sufficient mechanical strength can be obtained.

[0008] When the molded body is heat-treated to produce a solid activated carbon electrode, a part of the thermosetting resin is decomposed, gasified, and dissipated. Then, the above-mentioned problem does not occur. However, in the above-described production method, since the heat treatment is performed in a state in which the nitrogen gas is sealed in the furnace for the purpose of suppressing the oxidation of the activated carbon powder, the decomposition gas easily stays near the surface of the molded body, and Similarly, the decomposition gas is also likely to stay on the back surface of the molded body that is brought into close contact with the setter (base plate). Therefore, it is thought that since the staying gas hinders the decomposition of the thermosetting resin, a large amount of the thermosetting resin added excessively to the amount required for the solid activated carbon electrode remains after the heat treatment. Can be In addition, such a problem is caused by the fact that, for example, when heat treatment is performed in a state where a plurality of compacts are stacked via a plate-shaped setter in order to increase the mass productivity of the solid activated carbon electrode, the decomposition gas further accumulates. It becomes remarkable because it is easy.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a method for manufacturing an activated carbon electrode capable of sufficiently dissipating excess thermosetting resin. is there.

[0010]

In order to achieve the above object, the gist of the first invention is to form a molded body in which activated carbon powder is bonded by a thermosetting resin in a vacuum or non-oxidizing atmosphere. A method for producing an activated carbon electrode comprising a heat treatment step of carbonizing the thermosetting resin to obtain an activated carbon electrode by heat treating under the following conditions, wherein (a) decomposing the thermosetting resin during the heat treatment step. An exhaust step for forcibly exhausting gas is included.

[0011]

In this way, the decomposition gas of the thermosetting resin is forcibly exhausted in the exhausting step during the heat treatment step. Therefore, the decomposition gas of the thermosetting resin is prevented from staying near the surface of the molded body, and the decomposition is promoted. Therefore, the excessively added thermosetting resin is sufficiently dissipated, and a large amount of the thermosetting resin is prevented from remaining after the heat treatment step. The evacuation step of forcibly discharging the decomposed gas in a vacuum or a non-oxidizing atmosphere is a method of exhausting the decomposed gas by evacuating the furnace for performing the heat treatment and evacuating even during the heat treatment. Alternatively, a method in which an inert gas (a non-oxidizing gas) such as a nitrogen gas or an argon gas is caused to flow in and out, and the decomposition gas is simultaneously discharged, or the like can be employed.

[0012]

A second aspect of the present invention to achieve the above-mentioned object is to provide a molded article in which activated carbon powder is bonded by a thermosetting resin under vacuum or non-oxidizing conditions. A method of manufacturing an activated carbon electrode including a heat treatment step of obtaining an activated carbon electrode by carbonizing the thermosetting resin by heat treatment in an atmosphere, wherein (b) one surface of a plate-shaped member having unevenness on one surface. The heat treatment step is performed in a state where the molded body is brought into surface contact with the molded article.

[0013]

According to the second aspect of the present invention, the heat treatment step
The molding is performed in a state where the molded body is brought into surface contact with one surface of a plate-shaped member having unevenness on one surface. Therefore, the decomposition gas of the thermosetting resin generated during the heat treatment is exhausted from between one surface and the molded body through a flow path formed in the gap between the irregularities on the plate-shaped member and the molded body. Dissipated.
Therefore, the excessively added thermosetting resin is sufficiently dissipated, and a large amount of the thermosetting resin is prevented from remaining after the heat treatment step. Moreover, by interposing the above-mentioned plate-shaped member as a setter between a plurality of compacts, it is possible to stack and heat-treat the plurality of compacts without hindering dissipation of the decomposition gas. Mass productivity can be improved.

[0014]

In another preferred embodiment of the second invention, preferably, the plate-like member has a concave portion formed by providing irregularities on the one surface thereof, and is connected to an end surface of the plate-like member. , A gas passage extending from the inner position to the end face is formed. With this configuration, since a decomposition gas discharge path is formed between the plate member and the molded body, the decomposition gas is more easily discharged from between the plate member and the molded body. The residual amount of the curable resin is further reduced. Since the molded body in which the activated carbon powder is bonded by the thermosetting resin is porous, the decomposition gas can be dissipated through the inside of the molded body even if the concave portion is not continuous to the end face. In this way, it can be more easily dissipated.

Preferably, the plate-shaped member is made of a noble metal such as gold or platinum, a high melting point metal such as tungsten or molybdenum, a heat-resistant alloy such as a nickel-based corrosion-resistant heat-resistant alloy, a stainless steel material, or an alumina-based or zirconia-based material. It is made of ceramics such as glass, silica, magnesia, yttria, titania, and carbon, or heat-resistant glass.

[0016]

A third aspect of the present invention to achieve the above-mentioned object is to provide a molded product in which activated carbon powder is bonded by a thermosetting resin to a predetermined plate-like member. By performing a heat treatment in a vacuum or a non-oxidizing atmosphere in a state of surface contact with the surface, a method of manufacturing an activated carbon electrode including a heat treatment step of carbonizing the thermosetting resin to obtain an activated carbon electrode, (c) The method includes a step of forming irregularities on one surface of the molded body that is brought into surface contact with the plate-shaped member, and the heat treatment step is performed in a state where the irregularities are formed on one surface.

[0017]

According to the third aspect of the present invention, the irregularities are formed on one surface of the molded body in the unevenness forming step, and the irregularities are formed on the one surface of the molded body brought into surface contact with the plate-like member in the heat treatment step. Applied in state. Therefore, the decomposition gas of the thermosetting resin generated during the heat treatment is discharged from between the one surface and the plate member through a flow path formed in the gap between the unevenness on the molded body and the setter. Dissipated. Therefore, the excessively added thermosetting resin is sufficiently dissipated, and a large amount of the thermosetting resin is prevented from remaining after the heat treatment step. In addition, since the molded body itself has irregularities, even when a plurality of molded bodies are stacked via a setter and subjected to a heat treatment, the dissipation of the decomposition gas is not hindered. Performance can be improved.

[0018]

According to another aspect of the present invention, in the second and third aspects, the irregularities provided on the plate-like member or the molded body are formed by cracks, holes, pores, through holes, or on one or both sides. By forming grooves at predetermined intervals along a predetermined one direction or multiple directions, they are formed by the grooves and the remaining convex portions. In the former case, it is possible to form pores and pores by forming the plate-like member and the molded body to be porous, but after adding an appropriate resin and molding, the resin is removed by heating. In the process, cracks and voids may be formed chemically. In addition, etching or perforation may be used. In the latter case, for example,
Grooves can be formed by machining such as etching or grinding, but the grooves are provided on both sides along one direction so that the cross section becomes corrugated, or in two directions orthogonal to each other on one surface It is provided along.
When grooves are formed on both surfaces, the protrusions may be left at the same position on both surfaces, or the protrusions on the other surface may be located at positions between the protrusions left on one surface. A groove may be formed so as to remain.

[0019]

Embodiments of the present invention will be described below in detail with reference to the drawings. In the following examples, the dimensional ratios and the like of each part are not necessarily drawn accurately.

FIG. 1 is a diagram schematically showing a cross-sectional structure of an electric double layer capacitor 12 using an activated carbon electrode 10 manufactured by a manufacturing method according to one embodiment of the present invention. The capacitor 12 has a box shape as a whole, and has a pair of flat activated carbon electrodes 10, 10, and the pair of activated carbon electrodes 10, 10.
, Activated carbon electrodes 10, 10
, A pair of current collectors 16, 16, a pair of terminal plates 18, 18, a pair of fixing plates 20, 20, and a pair of current collectors 16, 20 provided on the side surfaces of the activated carbon electrodes 10. 1
6, and a pair of supports 24, 24 provided on both sides of the gasket 22 to support the fixing plates 20, 20, respectively.
For example, a 30 (wt%) sulfuric acid aqueous solution is injected as an electrolytic solution into the interior surrounded by the gasket 22.

The pair of activated carbon electrodes 10, 10 is, for example, about 1 (mm) in thickness, and is a porous activated carbon-carbon composite in which activated carbon is bound by a carbon tissue. The separator 14 has, for example, a thickness of 0.
It is made of glass fiber of about 1 to 0.2 (mm) and slightly larger in area than the activated carbon electrode 10. This prevents an electric short circuit caused by contact between the activated carbon electrodes 10, 10 and allows the electrolyte to freely flow. It is formed porous so that it can be distributed.

The current collectors 16, 16 are, for example, conductive sheets made of conductive rubber containing carbon, for example, having a thickness of about 0.2 (mm). By being sandwiched between the cells, partition walls are formed. That is, it has a bipolar electrode structure.

The terminal plates 18, 18 provided outside the current collectors 16, 16 are, for example, aluminum plates having a thickness of about 0.2 (mm) and an area similar to that of the activated carbon electrodes 10, 10. By applying a voltage to a pair of terminals (not shown) provided on the terminal plates 18, 18, the current collector 16,
Electric power is supplied to the activated carbon electrodes 10, 10 via 16. In addition, fixing plate 20, gasket 2
2. Each of the supports 24, 24 is made of a sulfuric acid resistant resin.

The above electric double layer capacitor 12 is assembled as follows. That is, first, each of the above-mentioned constituent members is sequentially laminated, and at this time, a sulfuric acid-resistant adhesive is applied between the gasket 22 and the supports 24, and fixed. Next, after the terminal plates 18, 18 are crimped to the current collectors 16, from both sides, the fixing plates 20, 20 are
It is fixed from both sides by bolts and nuts 26 in places. Finally, the electric double layer capacitor 12 is obtained by injecting a predetermined amount of the electrolytic solution through an injection hole (not shown) provided in the gasket 22 and sealing the same.

As shown schematically in FIG. 2, the electric double layer capacitor 12 configured as described above, when a voltage is applied, causes the surface of a large number of activated carbon particles 28 to have positive or negative ions in the electrolyte solution. (Ie H ⁺ or SO
₄ ^2- ) is adsorbed to form an electric double layer, and charging is performed. At this time, the activated carbon electrode 10
Is formed by bonding activated carbon particles 28 to each other by a carbon structure (not shown) derived from a thermosetting resin described later. Path), the mobility of the ions at this time determines the mobility of the ions, that is, the degree of the decrease in the capacitance during large-current discharge.

The activated carbon electrode 10 is manufactured, for example, according to the process shown in FIG. First, in step 1, for example, when the bulk density is about 0.20 (g / cm ³ ),
Activated carbon powder having a specific surface area of about several hundred to 2,000 (m ² / g) measured by the ET method is about 60 (wt%), and phenol resin as a thermosetting resin is about 40 (wt%). About 200 (wt%) (value based on the total amount of the mixture of activated carbon powder and phenolic resin) and then, for example, by mixing with a dry mixer, the activated carbon powder and phenolic resin are uniformly dispersed in the solvent. A slurry is prepared. The amount of the phenol resin added is an amount required for constituting the activated carbon-carbon composite material (an amount required for obtaining sufficient mechanical strength of the activated carbon electrode 10), and is described in the following steps. It is determined in consideration of the moldability necessary to obtain a desired molded body in the molding step of No. 3. The addition of the solvent may be performed, for example, after mixing the activated carbon powder and the phenol resin.

Next, in step 2, the above slurry is spray-dried at a predetermined temperature of about 200 (° C.) using, for example, a spray dryer to produce granulated particles in which activated carbon particles 28 are bonded with a phenol resin. . The granulated particles have, for example, an average particle size of about 100 (μm), a bulk density
It has a hollow spherical shape of about 0.35 to 0.41 (g / cm ³ ). In the above step 1, the amount of the solvent to be added and the like are appropriately set so that the characteristics such as the viscosity of the slurry are adjusted so that the granulated particles are hollow and the average particle size and the like have the above-mentioned target values.
In the subsequent step 3, the granulated particles thus obtained are cold-pressed at a pressing pressure of, for example, about 0.5 to 5 (tonf / cm ² ), for example, 70 × 50 × 1 (mm ) Produce a compact with a size of the order.

Then, as shown in FIG. 4, a plurality of the compacts 30 are stacked via a setter 32 corresponding to a plate-like member. Heat treatment at 900 ℃ for about 2 hours under reduced pressure of about ^-2 (Torr). That is, the heat treatment is performed in a state where the plurality of molded bodies 30 are sandwiched between the setters 32, respectively. The setter 32 is inserted for the purpose of preventing the molded bodies 30 from being joined to each other by the phenol resin partially melted in the course of the heat treatment. For example, 73 × 51 × 1 (mm) It is made of porous alumina or porous carbon having a porosity of about 20 (%) or more, having a large size and a large number of pores communicating with each other in the thickness direction and opening on both sides thereof. For this reason, the compact 3
On one surface of the setter 32 that is brought into surface contact with zero, irregularities due to the large number of pores are formed. Note that the setter 32 also plays a role in preventing the molded body 30 from warping during the heat treatment, and is therefore also provided at the uppermost portion as shown in FIG.

During the above heat treatment step, by performing evacuation in the evacuation step of step 5, phenol resin decomposed gas and the like generated in the furnace are discharged outside the furnace, and the pressure in the furnace is substantially constant. Is held. The evacuation may be continuously performed before the start of heating, but since the decomposition gas of the phenol resin cannot be generated at the beginning of the heating, the evacuation is temporarily stopped after the pressure is reduced to the above degree of vacuum. Alternatively, the process may be restarted after reaching the decomposition temperature.
As a result, a part of the phenol resin is carbonized and the excess is sufficiently dissipated, and the sintering density becomes 0.50 to
An activated carbon electrode 10, which is an activated carbon-carbon composite material having a bending strength of about 0.90 (g / cm ³ ) and a bending strength of 50 (kgf / cm ² ) or more, is obtained. Capacity and
An electric double layer capacitor 12 having a low capacity reduction rate of 30 (%) or less can be obtained. The rate of temperature rise and fall during the heat treatment is 100 (° C./h), and the degree of vacuum in the furnace is 10 ^{−2 to} 100 (Tor
r) It is appropriately determined within the range.

Table 1 below shows the characteristics of the electric double layer capacitor 12 using the activated carbon electrode 10 manufactured in accordance with the above-described manufacturing process, based on the heat treatment conditions in the above-described processes 4 and 5, specifically, the setter 32 and the exhaust gas. It shows the results of evaluation with various conditions changed. In the table, “setter” indicates the type (material, shape, etc.) of the setter 32 used for the heat treatment, “exhaust” indicates the presence or absence of the exhaust process and the exhaust method, and “capacity 1 capacity”.
2 decrease rate ”represents the characteristics of the electric double layer capacitor 12. Among the capacitor characteristics, "Capacity 1" is 0.1 (A)
When the constant current discharge is performed, the "capacity 2" indicates the capacitance (unit: F) when the constant current discharge is performed at 10 (A). For example, the constant voltage charge is performed at 0.9 (V) for 30 minutes. After 0.45
(V) constant current discharge at the above current value until C = (i ·
Δt) / ΔV [where the capacitance is C (F) and the discharge current is i
(A), the time required for the voltage drop is Δt (sec), and the voltage drop is ΔV (V)]. Also,
The “decrease rate” represents the ratio of the decrease in the capacitance at the time of large current discharge to the capacitance at the time of small current discharge expressed as a percentage [(capacity
2-capacity 1) / capacity 1] x 100 (unit:
%). In addition, other conditions, such as a raw material property and a heat treatment temperature, which are not shown in the table, are all the same.

[0031]

[Table 1]

Nos. 1 to 4 in Table 1 above use dense alumina or dense carbon as the setter 32 instead of the porous body. “None” in the “Exhaust” column indicates that, as in the conventional heat treatment process, an inert gas such as nitrogen gas is introduced into the furnace before the heat treatment is started, and the flow of the inert gas is stopped during the heat treatment. "VAC" indicates that the heat treatment was performed in the active gas atmosphere, and "VAC" indicates that evacuation was performed during the heat treatment. Therefore, in Nos. 1 and 2, the exhaust process for discharging the decomposition gas of the phenol resin generated during the heat treatment is not performed. As is clear from the table,
If the exhaust process is not performed, sufficient capacitor characteristics cannot be obtained. However, by performing the exhaust process, the capacitance is increased and the capacity reduction rate is reduced, making it suitable for applications requiring high power. Can be obtained. That is, by performing the evacuation step (vacuum evacuation) during the heat treatment, the decomposed gas of the phenol resin in the molded body 30 is discharged outside the furnace, so that the decomposed gas is prevented from staying in the vicinity. To promote the dissipation of phenolic resin,
A large amount of carbide (carbon) of the phenol resin added excessively for the purpose of enhancing the moldability is suppressed from remaining in the activated carbon electrode 10, and high capacitor characteristics can be obtained.

Nos. 5 to 14 use the above-described porous body or a plate-like member processed from metal, alumina, or carbon as the setter 32. In the “setter” column, “porous alumina” and “porous carbon” (Nos. 5 to 8) are both porous bodies, but the porosity of No. 7 is slightly reduced. The “punched metal” is, for example, a sheet made of an alloy having high heat resistance such as SUS310 and having a thickness of about 1 (mm).
A large number of round holes of 0.5 (mm) or φ1.0 (mm) are regularly provided. In the punching metal shown in the above table, round holes are provided independently of each other. For example, as shown in FIG. 5 (c), each hole passes through a circular hole provided in one direction. By forming a plurality of grooves that make the end faces continuous as described above, the round holes may be connected to each other and the end faces of the setter 32 may be connected to each other. The "corrugated material" has a corrugated shape as shown in FIG. 5 (e), and the height of the wave, that is, the groove depth is, for example, 0.8 (mm).
Has been around. The "lattice groove" is one in which a large number of grooves are provided on one surface along two directions orthogonal to each other, as shown in FIG. 5 (f). The lattice grooves are provided on both sides of the setter 32. As shown in FIG. 5 (d), the "keyway" is provided so that a plurality of longitudinal grooves extending in one direction are mutually offset on both surfaces. In those provided with these grooves, the numerical values represent the depth of each groove. As is clear from the figure, the lattice grooves, the key grooves, and the like are all provided so as to open to the end faces.

In the column of “exhaust”, “N ₂ flow” and “Ar flow” are replaced by vacuum exhaust of the furnace.
During the heat treatment, nitrogen gas or argon gas flowed into and out of the furnace, respectively. That is, in these cases, the heat treatment is performed in an inert gas stream, whereby the decomposition gas of the phenol resin generated in the furnace is discharged with the discharge of the inert gas. The flow rate of the inert gas flow is, for example, about 10 (l / min).
About 20 (vol%) per minute (min) of the total amount of gas in the furnace will be replaced with new inflow gas.

As is clear from the comparison of No. 5 with Nos. 1 and 2 in the above table, by using a porous material for the setter 32, the decomposition gas of the phenol resin passes through the pores formed in the setter 32. It is discharged from between the setter 32 and the compact 30. Therefore, also in this case, the decomposition gas is prevented from staying in the vicinity of the molded body 30, and the molded body 3
Since the dissipation of the phenol resin excessively contained in the phenol resin is promoted, the carbide (carbon) of the phenol resin
Is suppressed from remaining in the activated carbon electrode 10 in a large amount. However, Nos. 6 to 8 using similar setters 32
As shown in (1), by performing a heat treatment in a vacuum exhaust or an inert gas stream, that is, by performing an exhaust process, higher capacitor characteristics can be obtained. In spite of using a setter 32 having a similar porosity, No. 6 has a higher capacitance than No. 8, so that active exhaustion is performed. It is presumed that vacuum evacuation is more appropriate as an evacuation method than an inert gas air flow. In addition, since the capacitor characteristics of No. 7 are lower than those of Nos. 6 and 8, when the setter 32 is formed of a porous material, it is considered that the higher the porosity, the better. In the porous setter 32, since most of the pores are communicated with each other, the pores that are opened on one side and are brought into contact with the molded body 30 are also communicated with the end face. Thus, a discharge path for discharging the decomposition gas from between the setter 32 and the molded body 30 is formed.

In the case of using the punching metals No. 9 and No. 10, a plurality of gaps corresponding to the round holes of the punching metal are independently formed between the compact 30 and the setter 32. Become. However, as apparent from the fact that the sintered density of the activated carbon electrode 10 is as low as about 0.50 to 0.90 (g / cm ³ ) as described above, since the molded body 30 is formed porous, The decomposed gas generated in step (1) is discharged from the space between the setter (32) and the pores in the compact (30). Therefore, it is considered that sufficiently high characteristics can be obtained as shown in Table 1 above. However, since a larger gap formed by the round hole promotes generation of a decomposition gas, that is, dissipation of the phenol resin, When the round hole is large (No. 10), higher characteristics can be obtained. Note that this
As is clear from the results of Nos. 9 and 10, even in the case of heat treatment in an argon gas stream, the decomposition gas is discharged outside the furnace in the same manner as in the case of heat treatment in a nitrogen gas stream.
Higher characteristics can be obtained than a simple atmosphere heat treatment filled with an inert gas. When this punched metal is used, as described above, the discharge path of the decomposed gas generated between the molded body 30 and the setter 32 is limited to the pores in the molded body 30, and therefore, the porous body Although the characteristics are lower than those in the case of using the mold, a groove passing through a round hole is formed as shown in FIG. If the dissipation of the phenolic resin is promoted by ensuring the above, higher characteristics can be expected.

In Nos. 11 to 14, grooves of various shapes are provided in the setter 32. In each case, a flow path (discharge path) of a decomposition gas is formed between the setter 32 and the compact 30. Is ensured, the phenol resin contained in excess is sufficiently dissipated, and sufficiently high characteristics are obtained. However, compared to the case where another setter 32 is used,
No. 12 using a setter 32 provided with a groove of 0.1 (mm) depth
Is relatively low, it is considered that the depth of the groove is insufficient at this level. From these results, it is presumed that it is desirable to set the depth to about 0.2 (mm) or more when providing a groove. Therefore, as in the setter 32 used in Nos. 5 to 14, irregularities, that is, pores, holes, grooves, and the like that form a flow path for promoting the discharge of the decomposition gas can be brought into surface contact with the molded body 30. By providing it on one surface, it is possible to sufficiently dissipate excess phenol resin and reduce the amount of carbide remaining in the activated carbon electrode 10.

Table 2 below shows various changes in the manufacturing conditions of the molded body 30. `` Capacity 1 Capacity 2 Reduction rate ''
Is the same as in Table 1. In the table, Nos. 15 to 22 differ in the sintering density of the activated carbon electrode 10 by changing the ratio of the phenolic resin in the mixing step of the step 1, for example. If the ratio of the phenolic resin mixed in order to enhance the moldability is reduced, the molding density is reduced. Therefore, the sintering density can be adjusted by appropriately changing the ratio. Nos. 17, 18, and 19 correspond to N in Table 1 above.
The same as o.2,5,6 respectively. No.24 to 26
In the mixing step, a thermoplastic resin such as polymethyl methacrylate (polymethyl methacrylate; PMMA) or MC is added to the molded body 30 of No. 23, for example, at 20 (wt%).
To the surface of the sintered body by cracking as shown in FIG.
Macro holes as shown in (b) are formed.
That is, in Nos. 24 to 26, an unevenness forming step of forming unevenness on one surface of the molded body is performed during the heat treatment step. The form and size of these cracks and macropores are controlled by the amount of the resin added, and all are formed so as to communicate in the thickness direction. As the setter 32, a metal provided with a key groove in No. 14 of Table 1 is used.
When the setter 32 having another shape is used, it is considered that the characteristic value is different but the same tendency is exhibited.

[0039]

[Table 2]

When the density of the molded body 30 is changed as shown in Nos. 15 to 22, the lower the molding density, that is, the lower the sintering density, the more the decomposition gas of the phenolic resin becomes. Since it becomes easy to dissipate through the interior of the electrode 30 and the specific surface area of the activated carbon electrode 10 increases, high characteristics can be obtained. For example, when the sintering density is 0.90 (g / cm ³ ) or more, the dense body has almost no pores, so that the specific surface area decreases and the flow path of the decomposition gas is not secured in the molded body 30. For this reason, even if a porous body is used for the setter 32 and vacuum evacuation is performed during the heat treatment, not so high characteristics can be obtained, and particularly, the capacity reduction rate is hardly improved. On the other hand, when the sintering density is smaller than 0.90 (g / cm ³ ), since the specific surface area is sufficiently large, the decomposition gas is discharged outside the furnace by evacuation or the like, or By using a porous material to prevent the decomposition gas from staying with the compact 30 and reducing the amount of carbide remaining in the activated carbon electrode 10, extremely high characteristics can be obtained. That is, in order to discharge the decomposition gas during the heat treatment or to obtain a sufficient effect of securing the discharge path of the decomposition gas in the setter 32, the sintering density of the activated carbon electrode 10 should be smaller than 0.90 (g / cm ³ ). It is desirable to do. Although no particular data is shown, the mechanical strength tends to decrease as the sintering density decreases. Therefore, the sintering density is determined by comparing the capacitor characteristics and the mechanical strength when the electric double layer capacitor 12 is formed. It is desirable to decide in consideration of the balance.

As shown in Nos. 24 to 26, when cracks and macropores are formed, they function as an exhaust gas discharge path, and as apparent from the comparison with No. 23, The reduction in the amount of carbide remaining in the activated carbon electrode 10 improves the capacitor characteristics. In addition, “crack (small)” is, for example, a crack (crack) formed on the surface of a sintered body having an opening width of about 0.5 (μm), and “crack (large)” has an opening width of about 0.5 (μm).
It is about 5 (μm). As is clear from the table, in order to obtain high capacitor characteristics, it is desirable that the cracks be as large as possible within a range where the required mechanical strength can be obtained. The macropores formed in No. 26 have a diameter of, for example, about 10 (μm), and the porosity of the sintered body is increased by about 20 (%) by the formation of the macropores. Although no particular data is shown, in order to increase the efficiency of decomposed gas emission without significantly reducing mechanical strength,
It is preferable to reduce the diameter of the macropores and thereby increase the porosity, that is, increase the capacity of the macropores.

As described above, according to Nos. 3 and 4 of the present embodiment, the decomposition gas of the phenol resin is forcibly exhausted in the exhausting step of the step 5 during the heat treatment step of the step 4. You. Therefore, the decomposition gas of the phenol resin is prevented from staying near the surface of the molded body 30, and the decomposition is promoted. Therefore, the excessively added phenol resin is sufficiently dissipated, and a large amount of the phenol resin is prevented from remaining after the heat treatment step. Therefore, when the electric double layer capacitor 12 is configured, high capacitor characteristics can be obtained.

Also, in Nos. 5 to 8 of this embodiment,
The heat treatment step is performed in a state in which the molded body 30 is brought into surface contact with one surface of the setter 32 having unevenness on one surface. Therefore, the decomposition gas of the phenol resin generated during the heat treatment is discharged from one surface and the molded body 30 through a flow passage formed in the gap between the irregularities on the setter 32 and the molded body and dissipated. Let me do. Therefore, the excessively added phenol resin is sufficiently dissipated,
A large amount is prevented from remaining after the heat treatment step. In addition, by interposing the setter 32 between the plurality of molded bodies 30, without dissipating the decomposition gas,
Since a plurality of compacts 30 can be stacked and heat-treated, mass productivity of the activated carbon electrode 10 can be increased.

In the setters 32 used in Nos. 5 to 8, 11 to 14 in Table 1, the recesses formed by the provision of irregularities such as pores and grooves have By being continued to the end face, a gas passage reaching the end face from the inside position is formed. In this way, since a discharge path for the decomposed gas is formed between the setter 32 and the molded body 30, the decomposed gas is
Therefore, the residual amount of the phenol resin is further reduced. In addition, since the compact 30 in which the activated carbon powder is bound by the phenol resin is porous, the decomposition gas can be dissipated through the inside of the compact 30 even if the concave portion is not opened on the end face, even if the concave portion is not opened at the end face. In this way, it can be more easily dissipated.

In Nos. 24 to 26 of this embodiment,
In the unevenness forming step substantially performed during the heat treatment step, irregularities such as cracks and macropores are formed on one surface of the molded body 30.
The cracks and macro holes (ie, irregularities) are formed on one surface of the molded body 30 that is brought into surface contact with the surface of the molded body 30. Therefore, the decomposition gas of the phenol resin generated during the heat treatment is discharged from the one surface and the setter 32 through a flow path formed in the gap between the irregularities on the molded body 30 and the setter 32 and dissipated. Let me do. Therefore, the excessively added phenol resin is sufficiently dissipated, and a large amount of the phenol resin is prevented from remaining after the heat treatment step. In addition, since the molded body 30 itself has irregularities, even when a plurality of molded bodies 30 are stacked and heat-treated, for example, via the dense setter 32, dissipation of the decomposition gas is prevented. Therefore, the mass productivity of the solid activated carbon electrode can be improved.

While the embodiment of the present invention has been described in detail with reference to the drawings, the present invention can be embodied in still another embodiment.

For example, in the embodiment, vacuum exhaust or an inert gas stream such as a nitrogen gas or an argon gas is used to exhaust the decomposition gas during the heat treatment. The heat treatment may be performed in an inert gas stream.

In the embodiment, the grooves provided for forming the irregularities on the surface of the setter 32 are lattice grooves or key grooves. However, the present invention is not limited to these, and grooves having various shapes are provided. Is also good. For example, when stripe-shaped grooves are provided on both surfaces, the grooves may be provided along one direction and the other direction orthogonal to each other.

In the embodiment, cracks or macropores (irregularities) are formed in the molded body 30 in the heat treatment step by mixing a resin such as PMMA into the raw material. When performing cold pressure molding, irregularities may be formed at the same time as molding by using a molding die having irregularities formed on the pressing surface. Also, after the molding, the irregularities can be formed by machining such as cutting or drilling.

In the embodiment, the setter 32 is made of carbon, alumina, SUS310 or the like. However, for example, noble metals such as gold and platinum, refractory metals such as tungsten and molybdenum, nickel-based corrosion-resistant heat-resistant alloy, SU
It may be made of a heat-resistant alloy such as stainless steel other than S310, zirconia-based, silica-based, magnesia-based, yttria-based, titania-based ceramics, or heat-resistant glass.

In the examples, a phenol resin was added as a thermosetting resin at 40% by weight. However, the type and amount of the thermosetting resin to be added depend on the conditions of each step, the equipment used,
It is appropriately changed according to the target sintered density of the activated carbon electrode 10 and the like. For example, another thermosetting resin such as a urea resin or a melamine resin may be used, and the addition amount may be more or less than 40 (wt%).

In the examples, a predetermined compact was formed from the granulated powder by cold press molding in the forming step. However, for example, hot press molding such as hot press, extrusion molding, injection molding, The molding may be performed by a molding method, a powder rolling method, a doctor blade method, or the like.

In the examples, alcohol was used as a solvent for preparing the slurry. For example, water, ketones such as acetone, ethers such as diethyl ether, esters such as methyl acetate, and the like. Hydrocarbons such as hexane and aromatics such as toluene may be used. That is, various solvents can be used as long as the thermosetting resin is sufficiently dissolved in the mixing step to obtain good dispersibility. In the examples, the amount of the solvent added was 200 (wt%) with respect to the total amount of the mixture of the activated carbon powder and the thermosetting resin.
This amount is appropriately changed according to the viscosity of the mixture suitable for mixing and drying.

Further, in the embodiment, the case where the present invention is applied to the manufacture of the activated carbon electrode 10 used in the electric double layer capacitor 12 has been described. The same applies to the manufacture of the electrode 10.

The temperature at the time of the heat treatment is not limited to about 900 (° C.) as shown in the embodiment, but may be, for example, about 600 (° C.) or about 1000 (° C.). That is,
The temperature at the time of the heat treatment is appropriately changed within a range in which the activated carbon is not oxidized and the thermosetting resin is sufficiently dissipated and carbonized.

In the examples, the slurry was dried and granulated simultaneously with the spray drying method.
After the mixing step of Step 1, the remaining solvent is removed and solidified by, for example, drying the slurry in a vacuum using a vacuum drier, and then pulverized by, for example, an attritor. You may granulate by passing through.

Although not specifically exemplified, the present invention can be appropriately modified without departing from the gist thereof.

[Brief description of the drawings]

FIG. 1 is a view showing a cross-sectional structure of an electric double layer capacitor to which an activated carbon electrode manufactured by a manufacturing method according to an embodiment of the present invention is applied.

FIG. 2 is a schematic diagram for explaining the operation of the electric double layer capacitor of FIG.

FIG. 3 is a process chart showing a method for producing the activated carbon electrode of FIG.

FIG. 4 is a view for explaining a method of placing a compact in a heat treatment step of step 4 in FIG. 3;

FIGS. 5 (a) and 5 (b) show examples of a form in which irregularities are provided on the surface of a molded body, and FIGS. 5 (c) to (f) show examples of a form in which irregularities are provided on a setter. FIG.

[Explanation of symbols]

 10: activated carbon electrode 30: molded body 32: setter

Continued on the front page (72) Inventor Yukari Kibi 5-7-1 Shiba, Minato-ku, Tokyo Inside NEC Corporation (72) Inventor Takayuki Saito 5-7-1 Shiba, Minato-ku, Tokyo NEC Corporation In company

Claims (4)

[Claims] Activated carbon comprising a heat treatment step of carbonizing said thermosetting resin to obtain an activated carbon electrode by heat-treating a molded body in which activated carbon powder is bound by a thermosetting resin in a vacuum or a non-oxidizing atmosphere. A method for producing an electrode, comprising: an exhausting step of forcibly exhausting a decomposition gas of the thermosetting resin during execution of the heat treatment step. 2. Activated carbon including a heat treatment step of heat-treating a molded body in which activated carbon powder is bound by a thermosetting resin in a vacuum or a non-oxidizing atmosphere to carbonize the thermosetting resin to obtain an activated carbon electrode. A method for manufacturing an activated carbon electrode, comprising: performing the heat treatment step in a state where the molded body is in surface contact with one surface of a plate-shaped member having unevenness on one surface. 3. The plate-like member has a concave portion formed by providing irregularities on the one surface, and a recess formed by being continuous with an end surface of the plate-like member, thereby forming a gas passage reaching an end surface from an inner position. 3. The method for producing an activated carbon electrode according to claim 2, wherein 4. A heat treatment in a vacuum or a non-oxidizing atmosphere in a state in which a molded body in which activated carbon powder is bonded by a thermosetting resin is brought into surface contact with a predetermined plate-shaped member, thereby converting the thermosetting resin. A method of manufacturing an activated carbon electrode including a heat treatment step of carbonizing to obtain an activated carbon electrode, the method including a step of forming irregularities on one surface of the molded body that is brought into surface contact with the plate-shaped member, wherein the heat treatment step includes:
A method for producing an activated carbon electrode, wherein the method is carried out in a state where irregularities are formed on the one surface.