JP3537106B2 - Electric double layer capacitor electrode and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture a forming electrode without using any binder by heating a resin material within an atmosphere within a specific pressure range, at a melting temperature or higher of the resin, and at a temperature or lower where oxidation reaction starts for tentative baking. SOLUTION: Resin, PVDC, which becomes a raw material is heated at 200-500 deg.C which is equal to or more than the temperature of a heat-absorbing ending point due to a melt point or fusion and at the temperature or less of oxidation reaction point to obtain a tentatively baked resin. Then, the tentatively baked resin is cooled to normal temperatures and is ground by a vibration mill or a roll mill and then a powder tentatively baked resin is boiled in water. Then, the powder tentatively baked resin is subjected to pressurization tentative formation in an atmosphere of a pressure range of 0.01-10kg/cm<2> and is heated and baked at a temperature above the exidation reaction point, namely 500-900 deg.C, to obtain a porous carbon forming body. Therefore, since baking is performed while leaving a proper amount of volatile constituent in a material, a forming electrode can be manufactured without using any binder, thus obtaining a large-capacity capacitor.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrode for an electric double layer capacitor and a method for producing the same, and more particularly to an electrode for an electric double layer capacitor which is most suitable for obtaining a large capacitance and a method for producing the same.

[0002]

2. Description of the Related Art In recent years, accumulation of electric charges based on electric double layers,
That is, electric double-layer capacitors using the electric double-layer principle have been developed and commercialized.Since such capacitors can obtain a large capacitance, a small capacitor can be changed from a backup power supply for a semiconductor memory of an electronic device to a large-sized one. Are used for some of the applications of lead batteries in vehicles.

As an electrode material for this type of electric double layer capacitor, powdered activated carbon is obtained in a first step of pressurizing a carbon powder mixed with water at a pressure of 50 kg / cm 2 while heating it at about 700 ° C. Temperature of 700-1000 ° C 50-8
A method for producing a molded article of activated carbon from the second step of pressure molding at a pressure of 00 kg / cm @ 2 is disclosed in Japanese Patent Application Laid-Open No. 3-201520 filed by the present applicant.

In addition, the present applicant has made intensive research and development on electrodes for electric double layer capacitors, and as a result, the polyvinylidene chloride resin was heated in a non-oxidizing atmosphere, thereby causing atomic and molecular defects to generate pores. Electrode material formed with a layer was developed, and a patent application was filed for this (Japanese Patent Application No. Hei 6 (1994)).
-67827). This material is a porous carbon material having very fine pores, and is an electrode material having a higher capacity than conventional activated carbon.

[0005]

SUMMARY OF THE INVENTION The above-mentioned Japanese Patent Laid-Open Publication No. Hei 3-20
In the molding method disclosed in No. 1520, since carbon powder is used as a starting material, volatile components contributing to solidification evaporate during the carbonization process, so that solidification is difficult. There is a problem that the production cost is high and the molding density cannot be increased because it is necessary.When a binder is used to help solidify the carbon powder, when a capacitor is used, the electric capacity is reduced by the amount of the binder. I will. Further, when the resin, which is a raw material of carbon, is pulverized, molded and sintered, the volatile component is too large and the shape cannot be maintained. This is because a large amount of volatile components evaporate during firing, and the shape is destroyed by the evaporation power. That is, in the conventional method, the carbon powder could not be sufficiently solidified because the volatile component was too large or too small, or was not in an appropriate amount.

[0006]

SUMMARY OF THE INVENTION This invention is to solve the above problems, also in order to reduce the manufacturing cost, halo
The starting material is a thermoplastic resin containing a gas , and the resin is heated in an atmosphere having a pressure range of 0.01 to 10 kg / cm ² and at a temperature equal to or higher than the melting point of the resin or melting (softening flow) of the resin. A step of producing a calcined resin by heating at a temperature equal to or higher than the temperature at which the oxidation reaction starts and a temperature equal to or lower than the temperature at which the oxidation reaction starts, a step of cooling the calcined resin to room temperature to powder and producing a calcined powder resin, After molding the resin under pressure, a heating step of heating the resin at a temperature not lower than the temperature at which the oxidation reaction of the resin starts, or heating the calcined powder resin at a temperature not lower than the temperature at which the oxidation reaction starts while pressing the resin, to obtain a molded carbon body And a method for manufacturing an electrode of an electric double layer capacitor. Further, the present invention provides the above-mentioned manufacturing method.
Halogen-Free Thermoplastic Tree as a Starting Material in Agriculture
Using fat, before or before the step of producing the calcined powder resin
Adding halogen during the process of producing the calcined powder resin
Of electrodes for electric double-layer capacitors characterized by the following:
Is the way. The present invention may be manufactured by the manufacturing method of
An electrode of the obtained electric double layer capacitor, wherein said electrode has a ratio of pores having a pore diameter of 20 angstrom or more to the total surface area of the pores of said electrode being 10% or less. This is the electrode of the capacitor .

[0007]

As described above, according to the present invention, a resin material is placed in an atmosphere having a pressure range of 0.01 to 10 kg / cm @ 2 and at a temperature not lower than the melting point of the resin or melting (softening flow) of the resin. ), The material is heated at a temperature higher than the temperature at which the endothermic reaction is completed and at a temperature lower than the temperature at which the oxidation reaction starts, and calcined, so that firing is performed in a state where an appropriate amount of volatile components in the material is left. Thus, a shaped electrode can be manufactured without providing a capacitor, and a capacitor with a larger capacity can be provided.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The inventor of the present invention has invented a method for manufacturing a porous carbon molded article which is optimal as an electrode of an electric double layer capacitor, and has noticed that the mass change is due to evaporation of volatile components in the resin. Then, using a powdered polyvinylidene chloride resin (PVDC) suitable for producing porous carbon, the mass change and the heat of reaction during heating were investigated, and the heating temperature during heating and the evaporation of volatile components were investigated. The relationship with the amount was grasped, and the heating temperature at which volatile components effective for molding remained was obtained. 12 and 13 show the results. In these figures, the abscissa indicates the heating time, and the ordinate indicates the mass and the temperature. FIG. 12 shows the characteristics when the PVDC is heated in an oxidizing atmosphere (in the air), and FIG. 13 shows the characteristics when the PVDC is heated in a non-oxidizing atmosphere (in a nitrogen gas). The curve a in these figures is increased in proportion to the time axis at the heating temperature of the heating furnace, and the change in mass (curve b) and the characteristic of the reaction heat (curve c) at that time.
Is shown.

First, when heating in an oxidizing atmosphere (in the air), focusing on the reaction heat (curve c) in FIG.
At one point, the heat of reaction has decreased. This is due to an endothermic reaction due to melting, and this point is the melting point of the resin, and it was found that there was almost no change in mass at this point, that is, that volatile components in the resin were hardly evaporated. This endothermic reaction was completed at the point c2, and it was found that a sharp decrease in mass (evaporation of volatile components in the resin) occurred at this point. By the way, in the case of the PVDC tested this time,
The melting point was 175 ° C, and the end point of the endothermic reaction due to dissolution was 230 ° C. The same phenomena occur when the above-mentioned points c1 and c2 are heated in a non-oxidizing atmosphere. From this, it can be said that the reaction of c1 and c2 is not an oxidation, that is, a reaction involving combustion.

When the heating is further advanced, when the heating is performed in an oxidizing atmosphere (in the air), the reaction heat sharply increases at a point c3 of the curve c in FIG. 12, but the heating is performed in a non-oxidizing atmosphere. It was found that this phenomenon did not occur. From these facts, it was found that the point c3 when heated in an oxidizing atmosphere (in the air) was a reaction due to oxidation. By the way, P
In the case of VDC, the c3 point was 530 ° C. From the above analysis results, it was found that, in order to manufacture a molded body, a material having a volatile component contributing to molding can be obtained by heating at a temperature higher than the temperature of the point c1 or c2 and lower than the temperature of the point c3. .

Based on the above findings, the electrode of the electric double layer capacitor was manufactured by the manufacturing method shown in FIG.
The capacitor performance was measured. FIG. 1 will be described. First, the resin, PVDC, as a raw material is mixed with the melting point (c
1 point) or end point of heat absorption due to melting (c2 in FIG. 12).
(Point c3) and below the temperature of the oxidation reaction point (point c3 in FIG. 12) at 250 to 300 ° C. for 30 minutes to obtain a calcined resin. Next, the calcined resin was cooled to room temperature and pulverized with a vibration mill or a roll mill to obtain a powder calcined resin. This powder resin was boiled in water. This boiling step was not necessary, but boiling was more effective for capacitor performance.
Next, the powder calcined resin is pressure-temporarily molded, and is subjected to a temperature of 700 ° C. and 850 ° C. or higher than the oxidation reaction point (point c3 in FIG. 12).
Heating and sintering at a temperature of 2 ° C. yielded two types of porous carbon molded bodies. FIG. 11 shows the temperature pattern in the above manufacturing method. In FIG. 11, the holding time of the firing temperature is 1 to 15 minutes, but may be 1 hour or less.

Next, as a second embodiment, as shown in FIG.
A porous carbon molded body was obtained in the same manner as in Example 1 except that pressure and heat calcination were not performed in Example 1 (FIG. 1), and electrodes of an electric double layer capacitor were manufactured. The capacitor performance was measured.

As a third embodiment, as shown in FIG. 3, the first heating step of obtaining the calcined resin of the first embodiment (FIG. 1) is carried out in a steam atmosphere, and the pressure during heating is increased from no pressure to 20 kg / cm.
2 and the electrolyte was boiled and impregnated after the second heat treatment, and a porous carbon molded body was obtained in the same manner as in Example 1 except that microwave treatment was performed. It was manufactured and its pore size distribution and capacitor performance were measured.

FIG. 4 shows a process chart of the manufacturing method according to the fourth embodiment. In this embodiment, the resin is made of thermoplastic polybutylene terephthalate (hereinafter referred to as PBT) containing no halogen, and the first heating step of obtaining the calcined resin of Example 3 (FIG. 3) is carried out by chloride. A porous carbon molded body was obtained in the same manner as in Example 3 except that a pressure during heating of 3 kg / cm 2 was applied in a hydrogen atmosphere, electrodes of an electric double layer capacitor were manufactured, and the capacitor performance was measured.

FIG. 5 shows a process chart of the manufacturing method according to the fifth embodiment. In this example, the resin was PBT, and the manufacturing method was the same as that of Example 3 (FIG. 3) except that a step of mixing PBT and an aqueous hydrochloric acid solution was added before the first heating step of obtaining the calcined resin. A porous carbon molded body was obtained in the same manner as in Example 3, electrodes of an electric double layer capacitor were manufactured, and the capacitor performance was measured.

For comparison, PVDC was set at 700-9.
What was carbonized in a non-oxidizing atmosphere at 00 ° C. was mixed with a binder (Teflon resin) and molded to obtain a porous carbon molded body, and the capacitor performance was measured in the same manner. Furthermore, the distribution of the pore diameter and the capacitor performance were measured for six types of commercially available activated carbon (represented by symbols A to F).

FIG. 6 shows the experimental results of the capacitance of the electric double layer capacitor of these electrodes. Embodiment 3 in FIG.
The results are described for the case where the pressure at the time of the first heating is non-pressurized and the case where the capacitance is 3.0 kg / cm <2> at which the capacitance is maximized. From the results shown in FIG. 6, it was found that Example 1 had no binder, and had the same performance as the comparative example without pressurizing during heating and firing. A capacitance of 1.3 to 1.6 times as large as that of the example can be obtained. In the example 3, the calcination is performed under pressure and in a steam atmosphere, and a microwave treatment is performed after the forming and firing. It has been found that this leads to a three-fold increase in capacity. If microwaves are not used, 2
It is known that the same result can be obtained by performing the heat treatment at 00 ° C. for about 1 hour. Here, a microwave capable of shortening the time was used. Further, it was found that the capacities of Examples 4 and 5 were equivalent to those of Example 3. In Examples 4 and 5, PBT was exemplified as a resin containing no halogen.
For polyethylene terephthalate and polycyclohexane terephthalate, electrodes of an electric double layer capacitor were manufactured, and the performance of the capacitor was measured.
A performance equivalent to 5 was obtained. In Example 4, the pressure and heat treatment was performed in a hydrogen chloride atmosphere.
Performance equivalent to that of Example 4 was obtained even in a fluorine, bromine, or iodine atmosphere. Furthermore, the same performance as in Example 5 could be obtained also in the case of using a solution mixed with the resin in Example 5 instead of the aqueous hydrochloric acid solution, using an aqueous solution of fluorine, bromine, or iodine. Here, for comparison, in Example 4, a sample treated with a sulfuric acid atmosphere instead of a hydrogen chloride atmosphere, and in Example 5, a mixture of dilute sulfuric acid instead of a hydrochloric acid aqueous solution were trial-produced. Was manufactured, and the capacitor performance was measured. In each case, the capacitance was lower by 20 to 40% than in Examples 4 and 5. Based on the above, static electricity can be obtained by using a halogen-containing thermoplastic resin as a raw material for the electrodes of an electric double layer capacitor, or adding a halogen by a suitable method at an appropriate time in the manufacturing process of a thermoplastic resin containing no halogen. It has been found that an electrode having a large capacitance can be manufactured.

FIG. 7 shows the capacitance when the pressure in the first heating step is changed in the third embodiment, and FIG. 8 shows the fine capacitance with respect to the total surface area when the pressure in the first heating step is changed. Hole diameter 2
The ratio of the surface area of pores of 0 Å or more is shown.
FIG. 7 shows that when the pressing force in the first heating step was changed, the capacitance was maximum at a pressure of 3.0 kg / cm 2, and was minimum at no pressure and at a pressure of 10 kg / cm 2 or more. Was. When the pressure in the first heating step was changed from FIG. 8, the ratio of the surface area of the pores having a pore diameter of 20 Å or more to the total surface area was 3.0 kg.
/ Cm2, minimum pressure, no pressure and pressure 10kg / cm2
In the case of 2 or more, it was found that the ratio of the surface area of pores having a pore diameter of 20 Å or more to the total surface area was large. Incidentally, the reason for paying attention to the surface area of pores having a diameter of 20 angstroms or more is as follows.
This is because Angstrom is commonly used as a boundary. For example, in 1972, IUPAC (In
ternational Unionof Pore and Applied Chemistry)
Macropore: 500 Å or more, mesopore: 500 to 20 Å, micropore: 20 to
8 angstrom, sub-micropore: Classification of pores of 8 angstrom or less is defined.

FIG. 9 shows that the pressing force in the first heating step of the third embodiment is not pressurized, the pressure is 3.0 kg / cm 2, and the total surface area of seven types of commercially available activated carbons A to G is shown. The ratio of the surface area of pores having a pore diameter of 20 angstroms or more and the capacitance are shown. FIG. 10 is a graph of the data of FIG. 9, wherein the horizontal axis represents the ratio of the surface area of the pores having a pore diameter of 20 Å or more to the total surface area, and the vertical axis represents the capacitance. From these figures, the pore size 2 with respect to the total surface area
The ratio of the surface area of pores of 0 Å or more is 10%
It was found that the increase in capacitance was remarkable below.

[0020]

As described above, according to the present invention, the resin material is placed in an atmosphere having a pressure range of 0.01 to 10 kg / cm @ 2, at a temperature not lower than the melting point of the resin and not higher than the temperature at which the oxidation reaction starts. By heating and calcining, firing is performed with an appropriate amount of volatile components remaining in the material, so that a molded electrode can be manufactured without using a binder, and a capacitor with a larger capacity is provided. be able to. When a high-performance electrode is required, the resin material is placed in an atmosphere having a pressure range of 0.01 to 10 kg / cm 2, at a temperature not lower than the temperature at which the endothermic reaction accompanying melting (softening flow) of the resin is completed, and It can be obtained by heating and calcining at a temperature not higher than the temperature at which the oxidation reaction starts, and simultaneously calcining and calcining the calcined resin. As the above-mentioned resin material, a thermoplastic resin containing halogen is most suitable. However, a thermoplastic resin containing no halogen also exhibits the same performance as a resin containing halogen by adding halogen by an appropriate means. Electrodes can be manufactured.
The reason why the first heating temperature is set to “above the temperature at which the endothermic reaction accompanying the melting (softening flow) of the resin ends” is that if heating is performed at a temperature below the temperature at which the melting of the resin ends, the pores inside the carbon become It is because it is crushed and the surface area cannot be gained. Further, while an electrode formed using a binder has a problem in that the binder is deteriorated, the electrode of the present invention has no disadvantage. Furthermore, by performing the heat treatment in the steam atmosphere in the calcining step, the capacitance can be further improved.

[Brief description of the drawings]

FIG. 1 is a process chart showing a manufacturing process of a porous carbon molded body of Example 1 of the present invention.

FIG. 2 is a process chart showing a production process of a porous carbon molded body according to Embodiment 2 of the present invention.

FIG. 3 is a process chart showing a manufacturing process of a porous carbon molded body according to Embodiment 3 of the present invention.

FIG. 4 is a process chart showing a process for producing a porous carbon molded body according to Example 4 of the present invention.

FIG. 5 is a process chart showing a manufacturing process of a porous carbon molded body of Example 5 of the present invention.

FIG. 6 is a view showing one data obtained by testing the electrical performance of the porous carbon molded body according to the embodiment of the present invention.

FIG. 7 shows a first example of the porous carbon molded body according to the third embodiment of the present invention.
FIG. 6 is a diagram illustrating capacitance when the pressure in the heating step is changed.

FIG. 8 shows a first example of the porous carbon molded body according to the third embodiment of the present invention.
FIG. 4 is a diagram showing the ratio of the surface area of pores having a pore diameter of 20 Å or more to the total surface area when the pressure in the heating step is changed.

FIG. 9 shows a first example of the porous carbon molded body according to the third embodiment of the present invention.
Pressure in the heating process of no pressure and 3.0 kg
/ Cm 2, and the ratio of the surface area of pores having a pore diameter of 20 Å or more to the total surface area of seven types of commercially available activated carbons A to G, and the capacitance.

FIG. 10 is a graph showing the data of FIG. 9;

FIG. 11 is a diagram showing a temperature pattern in a process of manufacturing a porous carbon molded body according to an embodiment of the present invention.

FIG. 12 is a graph showing experimental results of a change in mass of a resin due to heating in the atmosphere and a heat of reaction.

FIG. 13 is a graph showing experimental results of a change in resin mass and a heat of reaction caused by heating in a nitrogen gas.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01G 9/058 C04B 35/52

Claims (8)

(57) [Claims] 1. A pressure range of a thermoplastic resin containing a halogen as a raw material at a first heating temperature not lower than a softening start temperature of the resin and not higher than a temperature at which an oxidation reaction starts.
A step of producing a calcined resin by heating in an atmosphere of 0.01 to 10 kg / cm ² , a step of cooling the calcined resin to room temperature to powder and producing a calcined powder resin, and adding the calcined powder resin. 2. A method for producing an electrode for an electric double layer capacitor, comprising: a step of pressure molding; and a step of producing a molded carbon body by heating at a second heating temperature equal to or higher than a temperature at which an oxidation reaction of the resin starts. 2. The method according to claim 1, wherein the first heating temperature is equal to or higher than the temperature at which the endothermic reaction accompanying the melting (softening flow) of the resin is completed and equal to or lower than the temperature at which the oxidation reaction starts. 2. The method for producing an electric double layer capacitor electrode according to item 1. 3. A process according to claim 1 or 2, wherein the electric double layer capacitor electrode, wherein the resin material is polyvinylidene chloride resin. 4. A raw material comprising a halogen-free thermoplastic resin.
As the resin melts (softens and flows)
Above the temperature at which the endothermic reaction ends, and the oxidation reaction starts
At a first heating temperature below the temperature, a pressure range of 0.01 to 10
Process to produce calcined resin by heating in an atmosphere of kg / cm ²
Cool the calcined resin down to room temperature to powder and calcine
Powder resin manufacturing process and pressurizing the calcined powder resin
Molding step and the temperature at which the oxidation reaction of the resin starts
A heating step of heating at the second heating temperature to obtain a molded carbon body;
Consisting of, before the step of producing the calcined powder resin or
Adding halogen during the process of producing the calcined powder resin
For manufacturing electric double layer capacitor electrodes
Law. 5. The method for producing an electric double layer capacitor electrode according to claim 1, wherein the step of producing the calcined resin is performed in a steam atmosphere. 6. The method according to claim 1, wherein the first heating temperature is from 200 ° C. to 50 ° C.
The method for producing an electric double layer capacitor electrode according to any one of claims 1 to 5, wherein the temperature is 0 ° C. 7. The method according to claim 7, wherein the second heating temperature is from 500 ° C. to 90 ° C.
The method for producing an electric double layer capacitor electrode according to any one of claims 1 to 6, wherein the temperature is 0 ° C. 8. The production method according to claim 1,
Electrode of an electric double layer capacitor manufactured by
The electrode of the electric double layer capacitor, wherein the ratio of the pores having a pore diameter of 20 angstroms or more to the total surface area of the pores of the electrode is 10% or less.