JP2002249307A - Method for reforming active carbon and method for manufacturing electric double layered condenser - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing an electric double layered condenser capable of improving electrostatic capacity and internal resistance and further lengthening the life of the condenser by using an active carbon having a good electrochemical stability as its electrode material. SOLUTION: This apparatus for manufacturing an electric double layered condenser is provided with heat treating means 10 which perform a heat treatment of an activated carbon at 400-900 deg.C, electrode forming means 20 which form polarizable electrodes by forming the heat treated active carbon into a given shape, arrange these electrodes so as to oppose each other via a separator, and form a main part of the condenser to make current collecting electrodes contact with the electrodes, electrolyte injecting means 30 which inject a given electrolyte into a case housing the main part of the condenser, and cell sealing means 40 which seal the case under condition of soaking the main part of the condenser in the electrolyte, and wherein each means are constituted to work in a specific atmosphere shielded from open air.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of reforming activated carbon and a method of manufacturing an electric double layer capacitor, and more particularly to a method of reforming activated carbon having stable electrochemical characteristics and using the activated carbon as an electrode material. The present invention relates to a method for manufacturing an electric double layer capacitor.

[0002]

2. Description of the Related Art In recent years, in a wide range of industrial fields such as portable information devices and electric vehicles, a technique of applying a secondary battery having a capacitor type storage battery such as an electric double layer capacitor to a driving power source has been studied. Generally, electric energy E that can be stored in a capacitor including an electric double layer capacitor
Is represented by the following equation, where V is the voltage between terminals of the capacitor (charging voltage) and C is the capacitance (capacitance of the capacitor). E = 1/2 · C · V ² (1)

From the above equation (1), it is necessary to increase the capacitance C or the terminal voltage V in order to store a larger electric energy E in the capacitor. Since the square value of (E) greatly affects the electric energy E, applying a high voltage between the terminals of the capacitor is extremely effective in terms of the electric characteristics of the capacitor.

Here, an electric double layer capacitor generally includes a pair of polarizable electrodes 101a and 101b to which activated carbon generated by making a carbon material porous by an activation treatment is applied as shown in FIG. , Disposed opposite each other with an insulating separator 103 interposed therebetween, and the pair of polarizable electrodes 101a,
101b has a stacked body in which individual collecting electrodes 102a and 102b are brought into contact with each other, and the stacked body is connected to a predetermined electrolyte 104
And sealed in a capacitor cell (case) 105. Although not shown, each of the collecting electrodes 102a and 102b is provided with an extraction electrode (terminal) extending outside the capacitor cell 105. The specific configuration of the electric double layer capacitor will be described later.

In such a method of manufacturing an electric double layer capacitor, conventionally, a coconut shell, a petroleum pitch,
About 3 carbonaceous materials such as petroleum coke and phenolic resin
Carbonization at a temperature condition of 00 to 900 ° C., and then, for example,
About 650 to 750 in atmospheres such as steam and carbon dioxide
Activated steam heated at a temperature of ℃, or mixed with an alkali such as potassium hydroxide (KOH) and sodium hydroxide (NaOH), and then mixed with an inert atmosphere for about 400 to 7
By performing an alkali activation or the like by heating at a temperature of 00 ° C., a large number of pores suitable for adsorption are generated on the surface of the carbonized carbonaceous material to make it porous, and finally the washing, drying, and pulverization steps are performed. To obtain activated carbon as an electrode material.

[0006]

However, in an electric double layer capacitor in which activated carbon generated by the above-described activation treatment is applied to a polarizable electrode, the above-described activation treatment (particularly, alkali activation) Under a high temperature condition, a chemical reaction occurs between the activator (for example, potassium hydroxide) and the carbonaceous raw material, and a chemically unstable functional group such as a carboxyl group (—COOH) or a hydroxyl group (—OH) or a gas. And the like, and these impurities are adsorbed and bonded to the pores formed on the surface of the carbonaceous raw material (activated carbon) activated by the activation, whereby the chemical stability of the activated carbon is improved.
In particular, the electrochemical stability has been impaired.

Here, after the activation treatment, the activated carbon is washed,
Although drying treatment is performed, these treatments have failed to sufficiently remove the adsorbed functional groups and impurities such as gas and improve the chemical stability. Therefore, when such activated carbon is applied to the polarizable electrode of an electric double layer capacitor, there is a problem that the capacitance is reduced or the internal resistance is increased due to impurities adsorbed on the surface pores of the activated carbon. Had.

In the above-described electric double layer capacitor, when an organic electrolytic solution is used as the electrolytic solution for immersing the laminate constituting the main constituent part, it is contained in the laminate and the capacitor cell. Alternatively, there is also a problem that the chemical decomposition of the electrolytic solution is promoted by the existing moisture, and the life of the electric double layer capacitor is shortened.

In view of the above-mentioned problems, the present invention provides a method for modifying activated carbon having good electrochemical stability and using the same as an electrode material to improve capacitance and internal resistance. Still another object of the present invention is to provide a method for manufacturing an electric double layer capacitor capable of extending the life of the capacitor.

[0010]

The activated carbon reforming method according to the present invention is characterized in that activated carbon produced by subjecting a carbon material to a predetermined activation treatment is degassed to a predetermined vacuum state, The heat treatment is performed under a temperature condition of 400 to 900 ° C.

That is, in the method of reforming activated carbon used for the polarizable electrode of the electric double layer capacitor, the activated carbon generated by the activation treatment with alkali or the like is reduced by 400%.
By performing the heat treatment at a temperature condition of ~ 900 ° C, the crystallization of the activated carbon is suppressed, and the reaction gas or the functional group or the like adsorbed on the surface pores of the activated carbon is released and desorbed, and Predetermined vacuum condition (atmospheric pressure condition)
, The desorbed impurities are removed from the vicinity of the surface pores. As a result, the activated carbon surface can be activated by improving the degradation of the chemical stability of the activated carbon caused by the chemically unstable impurities adsorbed on the surface pores, and has excellent electrochemical stability. Activated carbon can be provided.

Here, in the heat treatment step, it is preferable to perform heat treatment in a predetermined reducing gas atmosphere after degassing. That is, by supplying a reducing gas such as hydrogen or a mixed gas of a reducing gas and an inert gas to the heat treatment atmosphere, impurities desorbed from the surface pores of the activated carbon by the above heat treatment are reduced and the surface pores are reduced. Removed from the neighborhood. As a result, impurities released from the surface pores of the activated carbon can suppress dangling bonds that are re-adsorbed and bonded to the activated activated carbon surface, thereby improving the chemical stability of the activated carbon and improving the activated carbon surface. Can be activated.

Here, the specific surface area of the activated carbon produced by the activation treatment may be set to 120 m ² / g or less, whereby the activated carbon is applied to a polarizable electrode of an electric double layer capacitor. In addition, an electrode material that can increase the capacitance and reduce the internal resistance can be favorably manufactured.

In the heat treatment, at least the heat treatment conditions including the above temperature conditions and vacuum conditions are set so that the distance between the carbon rings constituting the activated carbon is 0.363 nm or less. Good. Accordingly, when the distance between the carbon rings is considered to be such that impurities such as a reaction gas and a functional group generated during the activation treatment of the carbon material are adsorbed on the surface pores of the activated carbon (0.364 nm or more). In comparison, since the heat treatment is performed so as to be narrower (0.363 nm or less), an activated carbon material which is released by releasing the bond of chemically unstable impurities can be manufactured, and the chemical characteristics of the activated carbon Of activated carbon with improved electrochemical stability.

The method of manufacturing an electric double layer capacitor according to the present invention is characterized in that activated carbon produced by subjecting a carbon material to a predetermined activation treatment is degassed to a predetermined vacuum state at 400 to 900 ° C. A step of performing a heat treatment under the temperature condition of, and forming the polarized electrode by shaping the heat-treated activated carbon into a predetermined shape, and disposing the polarizable electrode with an insulating separator interposed therebetween, and bringing the collector electrode into contact therewith. Forming the main part of the capacitor, injecting a predetermined electrolytic solution into a case containing the main part of the capacitor, and sealing the case in a state where the main part of the capacitor is immersed in the electrolytic solution. And wherein each of the steps is sequentially performed in a specific atmosphere shielded from outside air.

That is, in a method of manufacturing an electric double layer capacitor using activated carbon as an electrode material, the activated carbon generated by the alkali activation treatment by the heat treatment means is subjected to a heat treatment at a temperature of 400 to 900 ° C. Means, an electrode forming means, an electrolytic solution injecting means and a cell sealing means, each processing step for producing an electric double layer capacitor is performed in a specific atmosphere such as a reducing gas atmosphere or an inert gas atmosphere cut off from the outside air. Done in

Thus, while suppressing the crystallization of the activated carbon, the bonding of the impurities such as the reaction gas and the functional group adsorbed on the surface pores of the activated carbon is released by desorption, and the heat treatment atmosphere is maintained in a predetermined vacuum state. (Atmospheric pressure conditions)
Since the desorbed impurities can be removed from near the surface pores, it is possible to improve the deterioration of the chemical stability of activated carbon caused by the chemically unstable impurities adsorbed on the surface pores,
The activated carbon surface can be activated, and an electric double layer capacitor with improved capacitance and internal resistance can be provided. Further, since the electric double layer capacitor can be manufactured without being affected by moisture or the like contained in the outside air or the like, deterioration of the electric characteristics of the electric double layer capacitor due to moisture can be suppressed.

Here, it is preferable that the heat treatment is performed such that after degassing, the heat treatment is continued on the activated carbon in an atmosphere supplied with a predetermined reducing gas. In this case, a configuration having a reducing gas supply means for supplying a predetermined reducing gas may be employed.

That is, by supplying a reducing gas such as hydrogen or a mixed gas of a reducing gas and an inert gas to the heat treatment atmosphere by the reducing gas supply means, the functional group is removed from the surface pores of the activated carbon by the heat treatment. Since the hydrogen of the reducing gas is bonded to the dangling bond site generated by the desorption of impurities such as, the bonding of the desorbed impurity such as the functional group to the dangling bond site to be re-adsorbed is greatly suppressed. Therefore, it is possible to further improve the capacitance and the internal resistance of the electric double layer capacitor and provide an electric double layer capacitor having excellent electric characteristics.

In the above-described method for manufacturing an electric double layer capacitor, at least the step of forming the main part of the capacitor and the step of injecting the electrolytic solution into the case are performed in a predetermined atmosphere in which the water content is controlled. And having at least an inert gas supply means for supplying an inert gas for supplying an inert gas whose moisture content is controlled to the electrode forming means and the electrolyte solution injection means. It may be.

Thus, after the impurities are removed from the surface pores of the activated carbon in the heat treatment, the electrode is formed and immersed in the electrolytic solution without exposing the activated carbon surface having improved chemical stability to the moisture environment. Therefore, the chemical stability of the activated carbon can be favorably maintained, the capacitance and the internal resistance of the electric double layer capacitor can be improved, and the case where an organic electrolytic solution is used. Also, it is possible to prolong the life of the capacitor by suppressing the deterioration of the electrolytic solution.

Further, the activated carbon applied to the above-described method for manufacturing an electric double layer capacitor has a specific surface area of 120 m ^2.
/ G or less, and it has been experimentally demonstrated that according to this, the capacitance of the electric double layer capacitor can be increased and the internal resistance can be reduced.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a method for reforming activated carbon and a method for manufacturing an electric double layer capacitor according to the present invention will be described with reference to the drawings. <Manufacturing Apparatus> First, an apparatus for manufacturing an electric double layer capacitor according to the present invention will be described. FIG. 1 is a schematic configuration diagram showing one embodiment of an apparatus for manufacturing an electric double layer capacitor according to the present invention.

The capacitor manufacturing apparatus according to the present embodiment
Broadly speaking, the heat treatment means 10, the electrode formation means 20, the electrolyte injection means 30, the cell sealing means 40, the reducing gas supply means 50, the inert gas supply means 60, the heat treatment means 10, the electrode formation The means 20, the electrolyte injection means 30, and the cell sealing means 40 are provided with threshold valves PV1 to PV3 for isolating the processing atmosphere.

Hereinafter, each component will be described in detail.
The heat treatment means 10 is a heat treatment furnace main body (for example, a bake furnace or the like) that performs heat treatment on the activated carbon material at least at a temperature of 400 to 900 ° C. by a built-in heater or the like.
And a vacuum setting unit 12 such as a vacuum pump for setting the atmosphere inside the heat treatment furnace main body 11 (inside the furnace) to a predetermined vacuum state.
A heat treatment control unit 13 configured to control at least the temperature conditions and the vacuum state during the heat treatment, the supply amount of the reducing gas, and the like by controlling each of the units 11 and 12 and a reducing gas supply unit 50 described below; The activated carbon produced by the alkali activation is subjected to a heat treatment under predetermined heat treatment conditions (vacuum state, temperature condition, reducing gas supply condition, etc.), and the functional group adsorbed on the pores formed in the activated carbon A reforming process for removing impurities such as gas and gas is performed.

The electrode forming means 20 mixes a binder and a conductive material as necessary with the activated carbon heat-treated in the heat-treating means 10 and rolls and cuts the activated carbon into a predetermined shape. , A polarizable electrode (10 in FIG. 3)
1a and 101b), the polarizable electrode, the separator (see 103 in FIG. 3), and the collecting electrode (see 102a and 102b in FIG. 3) are connected to a capacitor cell (case; FIG. 3). And a cell assembly section 22 formed in a stack within the capacitor cell. A process for forming a main component (laminated body) of the electric double-layer capacitor including the polarizable electrode, the separator, and the collector in the capacitor cell. Do.

The electrolyte injection means 30 includes at least an electrolyte injection section 3 for injecting a predetermined electrolyte into the capacitor cell.
1 and a vacuum setting unit 32 for evacuating the capacitor cell to a negative pressure prior to the injection of the electrolyte, and by injecting a predetermined electrolyte into the capacitor cell, The main components are immersed in the electrolyte. The cell sealing means 40 is provided with at least an inlet sealing portion 41 for sealing an electrolyte inlet provided in the capacitor cell, and a main component of the electric double layer capacitor is immersed in the electrolyte. Is sealed.

The reducing gas supply means 50 adds (contains) hydrogen, which is a reducing gas, to a predetermined reducing gas, for example, argon gas (Ar), which is an inert gas, inside the heat treatment furnace body 11. ) Is supplied, and the activated carbon to be heat-treated is reduced. Here, the supply of the reducing gas is controlled by, for example, a heat treatment control unit 13 provided in the heat treatment unit 10.

The inert gas supply means 60 is controlled such that a predetermined inert gas, for example, the amount of water contained therein is reduced in the electrode forming means 20, the electrolytic solution injecting means 30, and the cell sealing means 40. By supplying the supplied argon gas (Ar), the electrodes are formed and the electrolytic solution is injected without exposing the activated carbon surface chemically stabilized by the heat treatment (reduction treatment) to a moisture environment.

The threshold valves PV1 to PV3 are provided between the heat treatment means 10 and the electrode forming means 20, between the electrode forming means 20 and the electrolyte injection means 30, and between the electrolyte injection means 30 and the cell sealing means 40, respectively. The processing atmospheres are isolated from each other so that each processing atmosphere can be set independently. Each threshold valve PV1-P
V3 is opened only before the start of processing and after the end of processing in each means, and carry-in / out of intermediate products (activated carbon or capacitor cells) to / from adjacent means is performed.

The apparatus for manufacturing a capacitor according to the present embodiment holds the processing atmosphere of each of the heat treatment means 10, the electrode formation means 20, the electrolyte injection means 30, and the cell sealing means 40 in addition to the above components. In such a state, a conveying means for carrying in and out the intermediate product or the like may be provided.

<Manufacturing Method> Next, a method of manufacturing an electric double layer capacitor using the apparatus for manufacturing an electric double layer capacitor having the above-described configuration will be described with reference to the drawings. FIG. 2 is a flowchart showing one embodiment of the method for manufacturing an activated carbon material according to the present invention, and FIG. 3 is an assembly configuration of an electric double layer capacitor manufactured by the method for manufacturing an electric double layer capacitor according to the present embodiment. FIG. In addition,
Here, description will be given with reference to the configuration of the above-described manufacturing apparatus (FIG. 1) as needed.

(STEP 1) Carbonization Step As shown in FIG. 2, first, a coconut shell as a raw material of activated carbon,
Coal, coal coke, petroleum pitch, petroleum coke, phenolic resin, etc.
After being carbonized by heat treatment at a temperature of 900 ° C., it is crushed to obtain a carbon material.

(STEP 2) Activation Treatment Step Next, the carbon material is mixed with an alkali and heated in an inert atmosphere at a temperature of approximately 500 to 900 ° C. to activate the carbon material to activate the alkali. Here, potassium hydroxide (KOH), sodium hydroxide (NaOH), or the like is applied as the alkali. Thereby, countless pores are formed on the surface of the carbon material,
A porous activated carbon having a predetermined specific surface area is produced.
After the alkali activation, the generated activated carbon is subjected to washing and drying steps to remove impurities mixed or attached to the activated carbon.

(STEP 3) Heat Treatment Step Next, as shown in FIG.
Is stored in the activated carbon storage container VS, and is carried into the heat treatment furnace main body 11 of the heat treatment means 10. Then, based on a command from the heat treatment control unit 13, first, the inside of the furnace is evacuated by the vacuum setting unit 12, and the air pressure is increased to, for example, approximately 1E-6 Torr. Heat treatment is performed to an arbitrary temperature condition of 400 to 900 ° C., for example, 600 ° C. by the heater provided in 11.

Here, when the temperature in the heat treatment furnace rises and reaches about 300 ° C., impurities which have not been removed by the washing and drying steps after the above-mentioned alkali activation (specifically, activated carbon by the alkali activation) The vacuum state (degree of vacuum) in the heat treatment furnace fluctuates due to the release of the bond of the functional group or gas adsorbed on the adsorption site in the surface pore of the heat treatment furnace, and the vacuum state is stabilized. By continuing the heat treatment in the heat treatment furnace body 11 and the degassing by the vacuum setting unit 12 until the heat treatment, the impurities are sufficiently released from the activated carbon. The temperature conditions (400 to 900 ° C.) applied to the heat treatment will be described later.

(STEP 4) Reduction treatment step The above heat treatment proceeds, and the vacuum state (degree of vacuum) in the heat treatment furnace
Is stabilized by the reducing gas supply means 50 based on a command from the heat treatment control unit 13, for example, hydrogen (H ₂ ) as a reducing gas is introduced into argon gas (Ar) as an inert gas. The mixed gas added (contained) at 3% is supplied into a heat treatment furnace (heat treatment atmosphere), and the heat treatment is continued (held) at a temperature of 600 ° C. for one hour. Then, the temperature in the heat treatment furnace is cooled to around room temperature while the mixed gas (reducing gas) is supplied. Thereby, impurities such as functional groups are released by the heat treatment, and a reduction reaction by a reducing gas occurs on the activated activated carbon surface to be stabilized, so that the once released impurities are again adsorbed on the surface pores of the activated carbon. The occurrence of dangling bonds (recombination) is greatly suppressed.

(STEP 5) Electrode forming step Next, the threshold valve PV1 provided between the heat treatment means 10 and the electrode formation means 20 is opened, and the activated carbon (electrode material) subjected to the heat treatment is transported to the electrode formation means 20. After that, the threshold valve PV1 is shut off. At this time, the atmosphere inside the electrode forming means 20 is set in advance in a state in which the inert gas supply means 60 is filled with an inert gas such as argon gas (Ar).

The electrode forming section 2 of the electrode forming means 20
According to 1, in the above-mentioned inert gas atmosphere, heat-treated activated carbon, a conductive agent and a binder, for example, 2 wt% (weight percent) of tetrafluoroethylene (PTFE) powder are added, and kneaded and rolled. Into a sheet having a thickness of 5 mm. Thereafter, an activated carbon material having a desired shape is cut out from the sheet, and vacuum-dried at, for example, a temperature of 200 ° C. for 12 hours to form a positive electrode and a negative electrode of the electric double layer capacitor (FIG. 3A). , 101a, 1
01b).

Next, FIG.
As shown in (a), a pair of polarizable electrodes 101a, 10a
1b is disposed to face one side via a separator 103 made of an insulating material such as polyethylene terephthalate, and a separate collecting electrode 102 made of a metal material such as aluminum is provided on the other surface of the polarizable electrodes 101a and 101b.
By contacting a and 102b, a main component (laminated body) STK of the electric double layer capacitor is formed as shown in FIG. And this main component STK
Are, for example, upper case 105a, lower case 105
b, housed in an insulating or conductive capacitor cell 105 consisting of a gasket 105c (FIG. 3 shows an insulating capacitor cell).

Here, in the case of using an organic electrolytic solution as the electrolytic solution in the electrolytic solution injection step described later, the moisture contained or present in the capacitor cell affects the electrical characteristics and life of the capacitor. Prior to the formation of the main component STK, the polarizable electrode (activated carbon) 1
The components other than the components 01a and 101b, that is, the separator 103, the collector electrodes 102a and 102b, and the capacitor cell 105 are baked under a temperature condition of about 200 ° C. in advance to remove water contained in each component (dehydration). Keep it.

(STEP 6) Electrolyte Injection Step Next, the threshold valve PV2 provided between the electrode forming means 20 and the electrolyte injection means 30 is opened to remove the capacitor cell 105 containing the main constituent part STK. After being transported to the electrolyte injection means 30, the threshold valve PV2 is shut off. At this time, the atmosphere inside the electrolyte injection means 30 is previously set to the same atmosphere as that of the electrode forming means 20, for example, argon gas (Ar) by the inert gas supply means 60.
, Etc., are set to be filled with an inert gas.

First, the inside of the capacitor cell 105 is evacuated to a negative pressure by the vacuum setting section 32 of the electrolyte injection means 30, and then, for example, N-ethyl-N- Methyl pyrrolidinium salt (ME
PYBF4) as an electrolyte, sulfolane + ethyl-methyl-carbonate (75 vol% SLF + 25 vol% EM
Organic electrolyte 1 having a concentration of 2.3 mol / L using C) as a solvent
04 is injected into the capacitor cell 105 through an electrolyte injection port (not shown) to immerse the main component STK.

(STEP 7) Cell sealing step Next, the threshold valve PV3 provided between the electrolyte injection means 30 and the cell sealing means 40 is opened to remove the capacitor cell 105 into which the electrolyte 104 has been injected. After being conveyed to the cell sealing means 40, the threshold valve PV3 is shut off. At this time, the atmosphere inside the cell sealing means 40 is previously set by the inert gas supply means 60 to the electrolyte injection means 3.
An atmosphere equivalent to 0, for example, a state filled with an inert gas such as an argon gas (Ar) is set.

Then, the electrolyte injection port of the capacitor cell 105 is sealed by the injection port sealing portion 41,
The electric double layer capacitor 100 as shown in FIG. 3C is completed. After that, the completed electric double layer capacitor 10
For 0, a high voltage equal to or higher than a specified charging voltage is applied only once to perform an electric activation process of performing a charge / discharge operation of a charge,
The electric double layer capacitor 100 is electrically activated.

In the electric double layer capacitor 100 shown in FIG. 3C, when an insulating material is used as the material of the capacitor cell 105 (the upper case 105a and the lower case 105b), the inside of the capacitor cell 105 An electrically independent extraction electrode extends from the collector electrodes 102a and 102b of the first and second collector electrodes 102a and 102b to form both terminals of an electric double layer capacitor. On the other hand, when a conductive material is applied, the upper case 105a and the lower case 105b that are electrically in contact with the respective collecting electrodes 102a and 102b and are electrically independent by the insulating gasket 105c are directly separated from each other by the electric double layer. Both terminals of the capacitor 100 can be used. In this embodiment, the case where the upper case 105a and the lower case 105b are made of an insulating material has been described.

According to such a method for manufacturing an electric double layer capacitor, in the heat treatment means 10, the activated carbon generated by the alkali activation treatment is heated at 400 to 900 ° C.
While performing the heat treatment under the temperature conditions of, during the heat treatment,
By supplying a predetermined reducing gas, while the impurities adsorbed on the surface pores of the activated carbon are desorbed and removed,
As a result, the activated carbon surface is reduced, so that dangling bonds in which impurities desorbed from the surface pores of the activated carbon are re-adsorbed and bonded to the activated carbon surface are suppressed, and the chemical stability of the activated carbon is improved.

[0048] A plurality of carbon rings (mainly benzene nuclei) spread in the plane direction of the activated carbon material (sample) before and after heat treatment (before / after heat treatment) in the activated carbon reforming method according to the present embodiment. When the distance between adjacent carbon ring layers of the laminate was measured by wide-angle X-ray diffraction, compared to before the heat treatment, after the heat treatment at 400 to 900 ° C., the adjacent carbon ring layers of the laminate were compared. The spacing between the layers was found to be smaller.

This is due to the steric hindrance caused by the adsorption of impurities such as functional groups and gases on the surface pores of the activated carbon material after the alkali activation treatment and before the heat treatment. Is wide (0.364 to 0.37)
0 nm), but 4% after the alkali activation treatment.
By performing a heat treatment at a temperature condition of 00 to 900 ° C,
The above impurities are desorbed and removed from the surface pores of the activated carbon material, and the distance between the carbon ring layers is small (0.358 to 0.358).
0.363 nm). Therefore, it has been clarified that the packing density of carbon atoms in the activated carbon is increased, so that the capacitance per unit volume can be increased.

Further, the method includes at least an electrode forming step of forming a main component of the electric double layer capacitor and an electrolytic solution injecting step of injecting an organic electrolytic solution into the capacitor cell.
A series of manufacturing steps of the electric double layer capacitor is performed in a specific atmosphere cut off from the outside air by heat treatment means, electrode forming means, electrolyte injection means and cell sealing means,
In addition, the processing atmosphere in the electrode forming means, the electrolytic solution injecting means and the cell sealing means is controlled by the inert gas supply means, so that the moisture content is controlled, without being affected by the moisture and the like contained in the outside air and the like. An electric double layer of electrolyte ions and activated carbon (polarizable electrode) is well formed, and the deterioration of the electric characteristics of the electric double layer capacitor is suppressed.
The life of the capacitor is prolonged.

In the heat treatment process shown in the present embodiment, the case where an inert gas (argon gas) to which hydrogen is added is applied as the reducing gas (mixed gas) has been described. However, the heat treatment may be performed in an atmosphere of hydrogen gas alone. Further, the reducing gas is not limited to hydrogen, and may be, for example, a saturated hydrocarbon gas such as methane and ethane. In addition, other than the reducing gas, a highly reactive unsaturated hydrocarbon gas such as ethylene or acetylene gas which can mainly remove a functional group having an oxygen atom may be used.

Further, a case has been described where an inert gas is used as a carrier gas used for the mixed gas, such as an argon gas. However, the present invention is not limited to this, and another rare gas may be used. In addition, the manufacturing conditions in the heat treatment shown in the above-described embodiment are at least 400 to
As long as the heat treatment is performed at a temperature of 900 ° C., the heat treatment may be performed under another pressure condition (vacuum state), a heat treatment time, or the like.

Here, the temperature conditions applied to the above-described heat treatment step will be described with reference to the drawings. FIG.
5 is a graph showing a result of a thermal analysis of activated carbon generated by a heat treatment step in the method for manufacturing an electric double layer capacitor according to the present embodiment. Here, differential thermal analysis (DTA) and thermogravimetry (TGA) are used as thermal analysis techniques, and experimental data of the suggestive heat DT and thermal mass TG are used using different coordinate axes (left Y axis and right Y axis). , Are shown in the same graph.

As shown in FIG. 4, the DT curve (Sdt) showing the change in the differential heat of the activated carbon during the heat treatment is represented by a heat treatment temperature of 37.
It has a curve consisting of an upwardly convex curved portion having a peak around 6.8 ° C. and a downwardly convex curved portion at a higher heat treatment temperature. This indicates that an exothermic reaction occurs in the upwardly curved portion, indicating that some decomposition reaction has occurred, and that an endothermic reaction has occurred in the downwardly convex portion, This means that unstable functional groups, moisture, and gas adsorbed on the surface pores of the activated carbon are decomposed and desorbed.

On the other hand, a TG curve (St) showing a change in thermal mass
g) has a tendency that the thermal mass is greatly reduced on the higher temperature side with the heat treatment temperature around 265.1 ° C. as a boundary.
This means that when the heat treatment temperature exceeds about 300 ° C., the unstable functional groups, moisture and gas adsorbed on the surface pores of the activated carbon are decomposed and desorbed and removed.

As described above, it has been found that impurities such as functional groups and gases adsorbed on the surface pores of activated carbon are desorbed from around about 300 ° C. of the heat treatment temperature, as shown in FIG. Judging from the experimental data comprehensively, in order to ensure that the desorption of impurities progresses and the activated carbon surface is activated well, a heat treatment temperature somewhat higher than 300 ° C, generally 400 ° C or higher is applied. Is preferred.

It has been found from various experiments by the inventor that if the heat treatment temperature is set extremely high (approximately 900 ° C. or higher), crystallization of the activated carbon proceeds and the electrochemical characteristics of the capacitor deteriorate. I have. Therefore, in order to improve the electrochemical stability of the activated carbon by suppressing the crystallization of the activated carbon and satisfactorily desorbing impurities such as gas and functional groups adsorbed on the surface pores of the activated carbon and improving the electrochemical stability of the activated carbon. ~ 900 ° C
It was concluded that it is appropriate to perform the heat treatment under the following temperature conditions.

Therefore, in the method of manufacturing an electric double layer capacitor according to the present embodiment, the activated carbon produced by the alkali activation treatment is subjected to a heat treatment at a temperature of 400 to 900 ° C. By performing a process of supplying a reducing gas such as the above, it is possible to satisfactorily remove chemically unstable impurities adsorbed on the surface pores of the activated carbon and to stabilize the activated activated carbon surface. it can.

Next, the electrical characteristics of the electric double layer capacitor manufactured by applying the above-described apparatus and method for manufacturing an electric double layer capacitor will be described with reference to the drawings. FIG. 5 shows the specific surface area of the activated carbon (sample) applied to the polarizable electrode and the electrical characteristics of the electric double layer capacitor before and after the heat treatment step in the electric double layer capacitor manufactured by the above-described manufacturing apparatus and manufacturing method. 9 is experimental data showing the relationship with. Here, the relationship between the specific surface area of the activated carbon composed of the samples A1 to A5, the capacitance per unit volume (capacitance density), and the internal resistance is shown.

As shown in FIG. 5, the specific surface area is 120 m ^2.
/ G in any of the activated carbon materials of Samples A1 to A5,
It was found that as the capacitance density generally increased, the internal resistance tended to decrease. This is due to the fact that impurities such as functional groups and gases are adsorbed on the surface pores of the activated carbon after the alkali activation treatment and before the heat treatment. And the capacitance density is low (30.6 to 3
2.6F / ml) while the internal resistance tends to be high (25.2-37.3Ω),
After the alkali activation treatment, heat treatment is performed at a temperature of 400 to 900 ° C., and a reducing gas such as hydrogen is supplied. In the activated carbon having a specific surface area of 120 m ² / g or less, the impurities are reduced to surface pores of the activated carbon. And the capacitance density is substantially increased (33.6 to 35.6).
F / ml) and the internal resistance is low (19.2 to 2
5.1 Ω) means that the state has been suppressed.

Therefore, according to the manufacturing method according to the present embodiment, the activated carbon produced by performing the heat treatment at a specific surface area of 120 m ² / g or less and at a temperature of 400 to 900 ° C. is used for the electric double layer capacitor. By applying it to a polarizable electrode, the chemically unstable impurities adsorbed on the surface pores of the activated carbon can be removed satisfactorily, and the electrochemical characteristics of the activated carbon can be stabilized. The internal resistance can be greatly reduced while the capacitance density is increased, and an electric double layer capacitor excellent in electric characteristics can be provided.

Next, the relationship between the heat treatment temperature and the capacitance density and internal resistance of the electric double layer capacitor will be described. FIG. 6 is correlation data showing the relationship between the heat treatment temperature and the capacitance density of the electric double layer capacitor.
4 is correlation data showing a relationship between a heat treatment temperature and an internal resistance of an electric double layer capacitor. Here, a case where the above-mentioned activated carbon having a specific surface area of 120 m ² / g or less (a sample A4 having a specific surface area of 32 m ² / g) is used as the activated carbon serving as a sample, and a ratio of 120 m ² / g or more are used. Activated carbon having a surface area (for example, a specific surface area of 360 m ² / g
Comparative study will be made on the case of using the sample X) having

As shown in FIG. 6, the specific surface area is 120 m ^2.
/ G or less of activated carbon (sample A4) as a polarizable electrode has a capacitance density of 3 when the heat treatment temperature is approximately 400 to 600 ° C.
A tendency to remarkably increase to 5-36 F / ml was observed. On the other hand, activated carbon (specimen X) having a specific surface area of more than 120 m ² / g, for example, a specific surface area of 360 m ² / g shows a capacitance density of about 30 F / ml regardless of the heat treatment temperature. No change was observed.

Further, as shown in FIG.
The internal resistance of an electric double layer capacitor using activated carbon (sample A4) of 0 m ² / g or less as a polarizable electrode is:
When the heat treatment temperature is approximately 400 ° C. or more, approximately 20Ω
The tendency to decrease significantly below was observed. On the other hand, activated carbon (specimen X) having a specific surface area of more than 120 m ² / g, for example, a specific surface area of 360 m ² / g, shows an internal resistance of about 18 to 22Ω regardless of the heat treatment temperature, and shows almost no change. Was not done.

The tendency of the change in the capacitance density and the internal resistance is such that the desorption of the impurities such as the functional group and the gas adsorbed on the surface pores of the activated carbon shown in FIG. Heat treatment temperature, ie, 300-400 ° C
According to this, in the activated carbon having a specific surface area of 120 m ² / g or less, the chemical stability is improved, the charge accumulation is performed favorably, and the capacitance density is increased.
It has been found that the internal resistance is greatly reduced and the electrical characteristics of the electric double layer capacitor are improved.

[0066]

As described above, according to the activated carbon reforming method of the present invention, the activated carbon produced by the activation treatment is heat-treated at a temperature of 400 to 900 ° C. While suppressing the crystallization of the activated carbon, the bonding of the impurities such as the reaction gas and the functional group adsorbed on the surface pores of the activated carbon is released and desorbed, and the heat treatment atmosphere is maintained at a predetermined vacuum state (pressure condition). As a result, the desorbed impurities are excluded from the vicinity of the surface pores. As a result, the activated carbon surface can be activated by improving the degradation of the chemical stability of the activated carbon caused by the chemically unstable impurities adsorbed on the surface pores, and has excellent electrochemical stability. Activated carbon can be provided.

Further, according to the present invention, in a method for manufacturing an electric double layer capacitor using activated carbon as an electrode material,
The activated carbon generated by the alkali activation treatment by the heat treatment means is subjected to a heat treatment at a temperature of 400 to 900 ° C., and the electric double layer is conducted by the heat treatment means, the electrode forming means, the electrolyte injection means and the cell sealing means. Each processing step for manufacturing the capacitor is performed in a specific atmosphere such as a reducing gas atmosphere or an inert gas atmosphere which is cut off from the outside air.

Therefore, while suppressing the crystallization of the activated carbon, the bonding of the impurities such as the reaction gas and the functional group adsorbed on the surface pores of the activated carbon is released by desorption, and the heat treatment atmosphere is maintained in a predetermined vacuum state ( Pressure conditions),
Since the desorbed impurities can be removed from near the surface pores, it is possible to improve the deterioration of the chemical stability of activated carbon caused by the chemically unstable impurities adsorbed on the surface pores,
The activated carbon surface can be activated, and an electric double layer capacitor with improved capacitance and internal resistance can be provided. Further, since the electric double layer capacitor can be manufactured without being affected by moisture or the like contained in the outside air or the like, deterioration of the electric characteristics of the electric double layer capacitor due to moisture can be suppressed.

Here, the heat treatment is preferably such that after degassing, the heat treatment is continued on the activated carbon in an atmosphere supplied with a predetermined reducing gas. In this case, a configuration having a reducing gas supply means for supplying a predetermined reducing gas may be employed.

That is, by supplying a reducing gas such as hydrogen or a mixed gas of a reducing gas and an inert gas to the heat treatment atmosphere by the reducing gas supply means, the gas was adsorbed on the surface pores of the activated carbon by the heat treatment. Since the activated carbon surface activated by the desorption of impurities is reduced, the impurities desorbed from the surface pores of the activated carbon are prevented from adsorbing and binding to the activated carbon surface again, thereby reducing the chemical stability of the activated carbon. Can be improved. Therefore, it is possible to further improve the capacitance and the internal resistance of the electric double layer capacitor and provide an electric double layer capacitor having excellent electric characteristics.

In the above-described method for manufacturing an electric double layer capacitor, at least the step of forming the main part of the capacitor and the step of injecting the electrolytic solution into the case are performed in a predetermined atmosphere in which the water content is controlled. And having at least an inert gas supply means for supplying an inert gas for supplying an inert gas whose moisture content is controlled to the electrode forming means and the electrolyte solution injection means. It may be.

Thus, after the impurities are removed from the surface pores of the activated carbon in the heat treatment, the surface of the activated carbon having improved chemical stability is not exposed to the moisture environment, and the electrodes are formed and immersed in the electrolytic solution. Therefore, the chemical stability of the activated carbon can be favorably maintained, the capacitance and the internal resistance of the electric double layer capacitor can be improved, and the case where an organic electrolytic solution is used. Also, it is possible to prolong the life of the capacitor by suppressing the deterioration of the electrolytic solution.

Further, the activated carbon applied to the above-described method for manufacturing an electric double layer capacitor has a specific surface area of 120 m ^2.
/ G or less, and it has been experimentally demonstrated that according to this, the capacitance of the electric double layer capacitor can be increased and the internal resistance can be reduced.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram illustrating an embodiment of an apparatus for manufacturing an electric double layer capacitor according to the present invention.

FIG. 2 is a flowchart showing one embodiment of a method for producing an activated carbon material according to the present invention.

FIG. 3 is an assembly configuration diagram of the electric double layer capacitor manufactured by the method for manufacturing an electric double layer capacitor according to the present embodiment.

FIG. 4 is a graph showing a result of thermal analysis of activated carbon generated by a heat treatment step in the method for manufacturing an electric double layer capacitor according to the present embodiment.

FIG. 5 is experimental data showing the relationship between the specific surface area of activated carbon (sample) applied to a polarizable electrode and the electrical characteristics of an electric double layer capacitor before and after a heat treatment step.

FIG. 6 is correlation data showing the relationship between the heat treatment temperature and the capacitance density of the electric double layer capacitor.

FIG. 7 is correlation data showing the relationship between the heat treatment temperature and the internal resistance of the electric double layer capacitor.

FIG. 8 is a cross-sectional view illustrating a schematic configuration of an electric double layer capacitor according to a conventional technique.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Heat treatment means 20 Electrode formation means 30 Electrolyte injection means 40 Cell sealing means 50 Reducing gas supply means 60 Inert gas supply means 100 Electric double layer capacitor

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Satoru Satorita 5 Casio Computer Hachioji Research Laboratory, 2951 Ishikawacho, Hachioji-shi, Tokyo F-term (reference) 4G046 HA10 HC01 HC03 HC08 HC12 5E082 AB09 BC14 LL21 MM23 MM24 PP06 PP10

Claims (6)

[Claims] An activated carbon produced by subjecting a carbon material to a predetermined activation treatment is subjected to a heat treatment at a temperature of 400 to 900 ° C. while being degassed to a predetermined vacuum state. Activated carbon reforming method. 2. The heat treatment is characterized in that heat treatment conditions including at least the temperature condition and the vacuum state are set such that the distance between carbon rings constituting the activated carbon is 0.363 nm or less. The method for reforming activated carbon according to claim 1, wherein 3. a step of subjecting the activated carbon produced by subjecting the carbon material to a predetermined activation treatment to a heat treatment at a temperature of 400 to 900 ° C. while degassing to a predetermined vacuum state; Forming the heat-treated activated carbon into a predetermined shape to form a polarizable electrode, disposing the polarizer opposite to each other with an insulating separator interposed therebetween, and forming a capacitor main part in contact with a collector electrode, Injecting a predetermined electrolytic solution into the case containing the capacitor main part, and in a state where the capacitor main part is immersed in the electrolytic solution,
And a step of sealing the case, wherein each of the steps is sequentially performed in a specific atmosphere cut off from the outside air. 4. The production of an electric double layer capacitor according to claim 3, wherein, after the degassing, the heat treatment is continued on the activated carbon in an atmosphere supplied with a predetermined reducing gas. Method. 5. The method according to claim 3, wherein at least the step of forming the main part of the capacitor and the step of injecting the electrolyte into the case are performed in a predetermined atmosphere in which the water content is controlled. Manufacturing method of electric double layer capacitor. 6. The method for manufacturing an electric double layer capacitor according to claim 3, wherein the activated carbon subjected to the heat treatment has a specific surface area of 120 m ² / g or less.