JP2003104710A - Solid state activated carbon and its producing method and electric double-layer capacitor using it and its producing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide solid state activated carbon which composes a polarizable electrode having a large electrostatic capacity and excellent electric charge and discharge cycle characteristics and an electric double-layer capacitor using it. SOLUTION: The solid state activated carbon which composes the polarizable electrode has the properties as follows. The specific surface area is 500 m<2> or more and 2,500 m<2> or less. The pore volume of pore 15 having diameter of 1 nm or less measured by an argon adsorption isothermal curve is 0.35-0.70 cc/g. The intensity ratio (ID/IG) of 1,360 cm<-1> band (ID) to 1,580 cm<-1> band (IG) at Raman spectroscopy is 0.5 or more.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to solid activated carbon, a method for producing the same, an electric double layer capacitor using the same, and a method for producing the same, and particularly to a polarizability having a large capacitance and excellent charge / discharge cycle characteristics. The present invention relates to solid activated carbon constituting electrodes, a method for producing the same, an electric double layer capacitor using the same, and a method for producing the same.

[0002]

2. Description of the Related Art In recent years, electric double layer capacitors have been used as a memory backup power supply in the electronics field and an auxiliary power supply for automobile drive motors because of their high capacitance. Then, activated carbon, which is a porous material, is used as a polarizable electrode that constitutes this electric double layer capacitor, and various studies have been conducted to achieve high capacity and low resistance.

As such solid activated carbon, for example, a carbonaceous material such as activated carbon or carbon black and an organic resin such as a fluoropolymer are kneaded and formed into a sheet by a known forming means such as a roll forming method. What was done was used.

However, as the polarizable electrode material for the electric double layer capacitor as described above, the performances of particularly high capacitance and low internal resistance are satisfied, and the recent demands for miniaturization of electronic parts are satisfied. Therefore, it is a porous structure that considers the minimization of the volume for a predetermined capacity and the impregnation property of the electrolytic solution, it is hard to cause cracks and damages, and it has excellent durability and mechanical properties even for general applications. Something is required.

In particular, the capacitance of an electric double layer capacitor is governed by the surface area of the polarizable electrode on which the electric double layer is formed, the capacitance per unit volume, the resistance of the polarizable electrode, etc. There is a close relationship with the size of the ions in the electrolytic solution forming the multilayer, and it is considered that the diameter of the pores and the specific surface area influence the capacitance.

Therefore, in order to increase the electrostatic capacity per unit volume of the polarizable electrode, a porous solid activated carbon having a large specific surface area is required within a range that does not impair durability and mechanical strength.

Regarding improvement of the solid activated carbon constituting such a polarizable electrode, for example, Japanese Patent Laid-Open No. 8-119614 has been proposed.
The one disclosed in Japanese Laid-Open Patent Publication is known. The activated carbon disclosed in this publication has a large specific surface area in a region called mesopore having a pore diameter of 20 Å or more, and thoroughly reduces a micropore region having a low contribution to performance,
It is intended to increase the capacitance by efficiently using the surface area.

Further, such a specific activated carbon is, for example, one in which the ratio of the specific surface area of the pore diameter of 20 Å or more after steam activation of the carbonaceous raw material to the total specific surface area is 0.30 or more is further alkalinized. It is described that it can be obtained by activating or carbonizing a carbonaceous raw material, followed by oxidation treatment and further alkali activation.

[0009]

However, since the size of the mesopores is larger than the size of the ions in the electrolytic solution used for the electric double layer capacitor, the electrolytic solution can be efficiently trapped in the pores of the activated carbon. Since it is difficult to form an electric double layer on the surface of activated carbon, only a low capacitance can be obtained, and since the pore size formed on the surface of activated carbon is large, the mechanical properties of the polarizable electrode are small. There was a problem of low strength.

Further, in such activated carbon, since the edge surface formed on the surface is small, the pore volume is small, and it becomes difficult to form the electric double layer, so that the electrostatic capacity per unit volume becomes low. there were.

Furthermore, the activated carbon is finally alkali-activated after activation of the carbonaceous raw material by steam or after carbonization and oxidation treatment, so that the surface including pores of the activated carbon is activated. Has a functional group containing an alkali metal, which decomposes during repeated charging and discharging of the polarizable electrode, resulting in an increase in resistance and a decrease in electrostatic capacity, resulting in a decrease in reliability.

Accordingly, the present invention provides a solid activated carbon which constitutes a polarizable electrode having a large electrostatic capacity and excellent charge / discharge cycle characteristics, a method for producing the same, an electric double layer capacitor using the same, and a method for producing the same. The purpose is to do.

[0013]

Means for Solving the Problems The solid activated carbon of the present invention has a specific surface area of 500 m ² / g or more and 2500 m ² / g or less and a pore volume of pores having a diameter of 1 nm or less obtained from an argon adsorption isotherm. Occupy 0.35-0.70 cc / g,
And the intensity ratio 1580 cm ^-1 band of 1360 cm ^-1 band in the Raman spectroscopy _{(I D) (I G)} (I D / I G) is characterized in that 0.5 or more.

According to this structure, even if the specific surface area of the solid activated carbon is 500 m ² / g or more and 2500 m ² / g or less, relatively large pores having a diameter of 2 nm or more are reduced, and conversely, the diameter is 1 nm or less. The pore volume of the pores is 0.35 to 0.
Since it is adjusted to 70 cc / g, the ions in the non-aqueous electrolyte used in the electric double layer capacitor are efficiently trapped in the pores, so that the electric double layer is formed on the surface of the activated carbon particles. The capacity of forming an electric double layer on the surface of the activated carbon particles is the basal plane which is a hexagonal net plane of graphite constituting the activated carbon particles, and It is known that the edge surface, which is a cross section, has a capacity of forming an electric double layer 10 times or more higher than that of the basal surface in the edge surface. However, in the Raman spectroscopy, the 1360 cm ⁻¹ band ( _ID ) 1580 cm ^{- 1} band (I _G) intensity ratio (I _D / I _G) is 0.5 or more, by increasing formation of edge surface to the surface of the activated carbon particles, electrostatic per unit volume of the electric double layer The capacity can be further improved.

The method for producing solid activated carbon of the present invention is as follows:
(A) a step of adding an organic binder to a carbonaceous raw material, mixing and shaping, and (b) a step of carbonizing the compact obtained in the step (a) at 700 ° C to 1100 ° C in a reducing atmosphere. , (C) impregnating the carbonized molded body with an alkali metal solution and drying the molded body in a reducing atmosphere at 700 ° C. to 10 ° C.
A step of performing alkali activation treatment at 00 ° C. for 1 to 10 hours,
(D) 700 ° C. to 1000 ° C. of the molded body after alkali treatment
And a step of forming a solid activated carbonaceous electrode by steam activation.

By using the above steps, activated carbon having many electric double layers on its surface can be formed, and
Particularly, by performing the steam activation treatment after the alkali activation treatment, it is possible to easily remove the alkali metal component that causes the increase in the resistance of the polarizable electrode.

The electric double layer capacitor of the present invention is characterized in that the above-mentioned solid activated carbon is used as a polarizable electrode constituting the electric double layer capacitor.

By using the above solid activated carbon capable of suppressing the increase in resistance of the polarizable electrode, an electric double layer capacitor having a large electrostatic capacity and excellent charge / discharge cycle characteristics can be formed.

The method for producing an electric double layer capacitor according to the present invention comprises (e) laminating at least two solid activated carbonaceous electrodes obtained in the above step with a porous separator interposed therebetween, and The method is characterized by including the steps of forming current collectors on the upper and lower surfaces of the body and (f) impregnating the solid activated carbonaceous electrode with an electrolytic solution.

By incorporating the solid activated carbon thus produced by the above method for producing solid activated carbon into an electric double layer capacitor as a polarizable electrode,
An electric double layer capacitor having excellent charge / discharge cycle characteristics can be easily formed.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (Structure) An explanation will be given based on FIG. 1 which is a schematic sectional view of an example of the electric double layer capacitor of the present invention. According to FIG. 1, the electric double layer capacitor has an electrolytic solution 1
A porous separator 3 having an insulating property is disposed between two polarizable electrodes 1 impregnated with 0, and a collector 5 is formed on the upper and lower surfaces of the polarizable electrode 1. Further, both ends of the polarizable electrode 1 and the separator 3 are sealed from the outside by a sealing member 7.

The polarizable electrode 1, as shown in the enlarged view of the main part attached to FIG. 1, is a solid activated carbon 11 formed by agglomeration of activated carbon particles 9 having a high specific surface area, and the solid activated carbon 11 It is composed of the carbon component 13 which is compounded for bonding.

According to the present invention, it is important that the specific surface area of the solid activated carbon 11 is 500 m ² / g or more because a large electrostatic capacity can be obtained. It is necessary to be 2500 m ² / g or less in order to secure the mechanical strength of the solid activated carbon 11 and prevent shedding from the solid activated carbon 11, and the specific surface area of the solid activated carbon 11 should be within such a range. As a result, self-discharge and deterioration of charge / discharge cycle characteristics can be suppressed and the electric resistance of the solid activated carbon 11 itself can be lowered.

Here, the crystal structure of graphite that becomes the activated carbon particles 9 will be described with reference to FIG. In FIG. 2, the crystal structure Gc of graphite is a layered lattice structure in which basal planes b that are hexagonal net planes are laminated, and the layered surface is an edge surface e. It is said that the basal plane b has a lower capacitance of the electric double layer than the edge face e because the ion penetration is blocked by the electron cloud shielding effect of π electrons, and thus the electrostatic capacitance is low.

Next, FIG. 3 shows an enlarged schematic view of a main part of the activated carbon particles 9.

As shown in FIG. 3, the activated carbon particles 9 constituting the solid activated carbon 11 of the present invention are aggregates of crystallites c having a layered structure, and the in-plane direction of the crystallites c is the basal plane b. The surface perpendicular to the base surface b is the edge surface e. In such activated carbon particles 9, the edge surface e is formed not only on the side surface of the crystallite c but also on the base surface b side. In addition, since the edge surface e is more likely to undergo a chemical reaction than the base surface b, the pores 15 are easily formed.

The diameter of the pores 15 formed on the surface of the activated carbon particles 9 can efficiently trap ions in the non-aqueous electrolyte used in the electric double layer capacitor, such as tetraethylammonium ion and tetrafluoroborate ion. For this reason, the thickness is set to 1 nm or less, and particularly 0.3 to 0.9 nm is important.

Further, the solid activated carbon 11 of the present invention contains H
In the pore distribution measurement obtained from the argon adsorption isotherm by the orvath-Kawazoe method (hereinafter referred to as the HK method), the volume ratio of the pores 15 having a diameter of 1 nm or less is 0.35 to 0.70 cc / g. It is important that the volume of the pores 15 having the pore diameter of 1 nm accounts for 40 to 65% of the total pore volume.

This is because when the volume of the pores 15 having a diameter of 1 nm or less obtained from the argon adsorption isotherm is less than 0.35 cc / g, ions in the non-aqueous electrolyte solution of the electric double layer capacitor, for example, tetraethylammonium ion, The number of sites where tetrafluoroborate ions and the like are efficiently trapped is small, it is difficult to develop a high electrostatic capacity, and the volume of the pores 15 is 0.70 cc.
If it exceeds / g, the solid activated carbon 11 has a large number of pores 15, so that the mechanical strength becomes extremely poor and handling becomes impossible. Having stable handling and high capacitance, considering wide application to other fields,
A range of 0.40 to 0.65 cc / g is particularly preferably used.

Further, according to the present invention, the edge surface e and the basal surface b are 1360c in Raman spectroscopy of a carbon material.
m ^-1 band (I _D) intensity ratio 1580 cm ^-1 band (I _G) of the (I _D / I _G) is important to be 0.5 or more, it can appear more edge surfaces e . In particular, the Raman intensity ratio (I _D / I _G ) is preferably in the range of 0.55 to 1.2 for the purpose of increasing the bond between the activated carbon particles 9 and ensuring the mechanical strength as well as the capacitance.
The crystal structure of this crystallite c is substantially the same as the crystal structure of graphite as shown in FIG.

Further, the mechanical strength of the polarizable electrode 1 is 3 MPa or more in terms of mechanical reliability that can withstand vibration, shock, etc. during handling and use during manufacturing of the electric double layer capacitor. It is particularly desirable that the pressure is 6 MPa or more.

As the electrolytic solution 10 to be impregnated in the polarizable electrode 1, an aqueous solution of sulfuric acid, nitric acid or the like, propylene carbonate, γ-butyrolactone, N, N-dimethylformamide, ethylene carbonate, sulfolane, 3-methylsulfolane, etc. It is possible to use an organic solution in which an organic solvent of (4) and an electrolyte such as a quaternary ammonium salt, a quaternary sulfonium salt, a quaternary phosphonium salt are combined.

Further, the separator 3 is formed of an organic film such as pulp, polyethylene, polypropylene or the like, a glass fiber non-woven fabric or the like, and ceramics or the like, and is formed to insulate the polarizable electrodes 1 from each other. It is formed of a porous body capable of permeating the ions in the electrolytic solution 10 contained in the electrode 1.

Further, the current collector 5 is formed by conductive butyl rubber having conductivity, aluminum foil, plasma spraying of aluminum, etc., and can exchange charges with the polarizable electrode 1. Moreover, the sealing member 7 is made of synthetic rubber or the like, and the current collector 5 and the sealing member 7 can prevent the electrolytic solution contained in the polarizable electrode 1 from leaking to the outside.

(Production Method) An example of a method for producing the above-mentioned solid activated carbon will be described.

As the carbon raw material, carbonaceous raw materials such as coconut shell, wood and resin, and activated carbon prepared by chemical activation or gas activation of the carbonaceous raw material can be used. Among them, the cost and the pore volume are large. Coconut shell activated carbon is preferred. Other than that, carbon black, carbon fiber, coal, etc. can be used.

The shape is spherical, flake-shaped, protrusion-shaped, fibrous or amorphous, and is not particularly limited, and may be granular, granular or fibrous. The particle size is preferably 5 to 50 μm.

A predetermined amount of organic binder is added to and mixed with each of the above-mentioned activated carbon raw materials in an amount such that the amount of carbon component after firing is 5 to 50% by mass. As the organic binder, phenol, Teflon (registered trademark), coal tar, polyvinyl butyral (PVB), polyvinyl formal (PV
Examples thereof include known organic binders such as polyvinyl acetals such as FM) and vinyl acetate. Among them, polyvinyl butyl alcohol (PVB) is most preferable in terms of moldability and strength of the resulting solid activated carbon.

Each of the obtained molding raw materials is molded into a predetermined shape by a known molding means such as a press molding method, a doctor blade method, an extrusion molding method, a calender roll method, a roll molding method, etc., to produce a tape-shaped molded body. . As a forming method, roll forming is preferable because it is easy to form a tape-like product with high productivity and the density of the formed body can be increased. The carbon material is dried in air at a temperature of 100 ° C or higher.

Next, a plurality of the above tape-shaped molded bodies are
It is integrated by thermocompression bonding at 60 to 100 ° C. and 20 to 50 MPa. Alternatively, an integral molding is formed by applying a contact liquid, an adhesive or the like between the tape-shaped moldings and adhering them. By closely adhering the tape-shaped molded body in this manner, delamination in the heat treatment described later can be prevented.

Next, the molded body was placed in a non-oxidizing atmosphere for 7 minutes.
00 to 1100 ° C, 1 to 5 hours, especially 800 to 900
The organic binder component is carbonized by carbonization at 1 ° C. for 1 to 5 hours, and the activated carbon particles 9 are sintered and integrated to form a sintered body. In this way, the ratio of the carbon component 13 existing between the solid activated carbons 11 to the solid activated carbons 11 can be set to 5 to 50% by mass, whereby the sinterability and the bondability between the solid activated carbons 11 are increased. be able to.

The reason why the firing temperature is limited to the above range is that if the temperature is lower than 700 ° C., the sintering between particles is insufficient and the strength of the structure is lowered. Conversely, if it is higher than 1100 ° C. This is because the sintering proceeds too much, it is difficult to form the desired pores 15 even if the alkali activation treatment described below is performed, and the capacitance of the capacitor decreases.

According to the present invention, the molded body containing the activated carbon particles 9 is carbonized (calcined) under the above conditions,
The binding force of the edge surface e can be increased. Moreover, since the polarizable electrode 1 formed of the solid activated carbon 11 of the electric double layer capacitor of the present invention is activated after carbonizing the molded body, it is not necessary to add an organic binder after activation. The high specific surface area of the activated carbon particles 9 can be maintained, and the electrostatic capacity of the electric double layer capacitor can be improved.

Next, the above-mentioned sintered body is treated with potassium hydroxide (KO).
H), sodium hydroxide (NaOH), barium hydroxide (Ba (OH) ₂ ), calcium hydroxide (Ca (O
H) ₂ ) etc. in an alkali metal or alkaline earth metal aqueous solution or zinc chloride (ZnCl ₂ ) aqueous solution,
After drying at 50 ° C to 100 ° C, 700 ° C to 1000 ° C, particularly 700 ° C to 900 ° C in a vacuum or a non-oxidizing atmosphere.
Process at 1 ° C for 1-10 hours. Particularly, the activation treatment is 3 to 5
Time is desirable.

The reason why the alkali activation temperature is limited to the above range is that when the temperature is lower than 700 ° C., it is difficult to form the edge surface e, and the Raman intensity ratio ( _ID / _IG ) value becomes low. This is because if the temperature is higher than 1000 ° C., the surface of the activated carbon particles 9 is excessively shaved, so that the volume of the pores 15 becomes large and the volume of the pores 15 having a diameter of 1 nm or less decreases.

Since the alkali activation method of the present invention is a method of impregnating with an alkaline solution and heating, after the alkali metal and / or alkaline earth metal has penetrated into the activated carbon particles 9, the alkali metal and / or The chemical reaction between the alkaline earth metal and the activated carbon particles 9 progresses, and pores 15 are formed from both surfaces of the basal plane b and the edge surface e of the activated carbon particles 9 due to carbonization of carbon. In this way, the base surface b side is scooped by the alkali activation, so that a new edge surface e is formed on the base surface b side.
Can be formed. Further, by activating the alkali after the carbonization treatment as described above, the disappearance of the edge surface e can be suppressed, and as a result, the existence ratio of the edge surface e with respect to the base surface b can be increased.

Next, the alkali-activated sintered body is heated at a temperature of 700 ° C. to 1 in an atmosphere of steam or carbon dioxide.
The treatment is performed at 000 ° C. for 1 to 10 hours. Especially, the temperature is 7
00 ° C to 900 ° C, and the activation treatment time is preferably 3 to 5 hours.

Further, the steam activation temperature is limited to the above range because it is difficult to remove the alkaline component which affects the cycle characteristics when the steam treatment temperature is low, and conversely, when the steam treatment temperature is high, the Not as much as activation,
Also in this case, the volume of the pores 15 becomes large and the volume of the pores 15 having a diameter of 1 nm or less decreases.

By carrying out the activation treatment in the atmosphere of water vapor or carbon dioxide after the alkali activation as described above, the pores 15 can be formed over the inside of the activated carbon particles 9 as compared with the activation in the atmosphere, and in particular, the edge surface can be formed. It is possible to form small pores 15 in e.

By this steam activation, a functional group containing an alkali metal (for example, -COON) attached to the surface of the activated carbon particles 9 including the edge surface e by the alkali activation treatment.
a)) can be removed. In particular, by setting the alkali activation treatment condition in vacuum to a temperature of 700 to 1000 ° C. and a treatment time of 1 to 10 hours, and subsequently setting the steam activation treatment condition to a temperature of 700 to 1000 ° C. and a treatment time of 1 to 10 hours. , a specific surface area of 500m ² / g or more 2500m ² /
Diameter less than 1g, diameter 1nm obtained from argon adsorption isotherm
Accounting for volume 0.35~0.70cc / g of pores 15 below, and 1580 cm ^-1 band (I _G) intensity ratio of 1360 cm ^-1 band in the Raman spectroscopy _{(I D) (I D /} I It is possible to form the solid activated carbon 11 having _{G 2} ) of 0.5 or more, and in this way, the solid activated carbon 11 having a specific specific surface area, pore size distribution and crystal plane distribution can be obtained.

If the heat treatment temperature for activation with alkali, water vapor or carbon dioxide is lower than 700 ° C. or shorter than 1 hour, the activation will be insufficient and the ratio of the edge surface e to the base surface b will be determined by Raman spectroscopy. It becomes difficult to obtain a strength ratio ( _ID / _IG ) of 0.5 or more by the method, and a desired specific surface area cannot be obtained. If the activation heat treatment temperature exceeds 1000 ° C. or is longer than 10 hours, the activation will proceed too much and the strength will decrease.

Next, in order to produce an electric double layer capacitor using the solid activated carbon 11 produced as described above, the sealing member 7 is arranged on the outer peripheral surface of the solid activated carbon 11 and the separator 3 is interposed therebetween. Then, the polarizable electrode 1 is laminated, and the polarizable electrode 1 is impregnated with the electrolytic solution 10. Then, the current collector 5 is formed on the upper and lower surfaces of the laminated body formed by the polarizable electrode 1 and the separator 3 to manufacture an electric double layer capacitor.

In this case, as a method of forming the current collector 5, a paste containing the same components as the current collector 5 is applied and baked, a plate-shaped current collector 5 is attached, or thermal spraying is performed. Can be formed.

As another method, the alkali activation of the solid activated carbon 11 may be carried out after laminating the carbonized (fired) -treated plate-like body for producing the polarizable electrode 1 and the separator 3. However, in this case, the separator 3 is
It is desirable to have heat resistance and alkali resistance that do not deteriorate due to alkali activation, and by using this method, the risk of damaging the activated carbon structure during manufacturing is reduced.

Similarly, in the steam activation, the polarizable electrode 1 is also used.
It may be carried out after laminating the carbonized (fired) -treated plate-like body and the separator 3 for producing the above. In this case, the separator 3 may have heat resistance and water resistance that are not deteriorated by steam activation. Desirably, the use of this method reduces the risk of damage to the activated carbon structure during manufacture.

The electrolytic solution 10 to be impregnated in the polarizable electrode 1 used in the electric double layer of the present invention is an aqueous solution of sulfuric acid, nitric acid or the like, propylene carbonate, γ-butyrolactone, N, N-dimethylformamide. Organic solvents such as ethylene carbonate, sulfolane, and 3-methylsulfolane, and quaternary ammonium salts, quaternary sulfonium salts,
An organic solution in which an electrolyte such as a quaternary phosphonium salt is combined can be used. Further, the solid activated carbon 11 produced by the above production method is analyzed and evaluated by the following method. First, the specific surface area of the activated carbon particles 9 is determined by the BET formula by measuring the volume of the adsorbed gas by the N ₂ gas adsorption method.

The pore size distribution of the activated carbon particles 9 is Shimadzu-
H using Micrometric Asap 2010M type
The pore size distribution can be measured from the argon adsorption isotherm by the K method, and the ratio of the volume of pores having a pore size of 1 nm or less can be determined from the mass of the activated carbon particle 9 sample.

Further, the edge surface e ratio formed on the activated carbon particles 9 was measured by using a Raman spectrometer manufactured by JASCO,
The solid activated carbon was measured with a 4.5 nm argon laser beam to obtain a Raman spectrum, and G near 1580 cm ^-1 was measured.
-Band (I _G) for 1360 cm ^-1 vicinity of D-
The area ratio of band (I _D ) can be obtained.

[0059]

[Example] 1 part of polyvinyl butyral was added to 100 parts by mass of coconut husk activated carbon powder having a BET value of 1500 m ² / g.
00 parts by mass was added, and the mixture was stirred with a high-speed stirrer, and the obtained powder was mesh-passed with 40 mesh to obtain a raw material for molding. Next, the obtained forming raw material is roll-formed under predetermined conditions to obtain a flat plate-shaped formed body, and the formed body is held at a temperature of 200 ° C. for 48 hours in the air, and then in a vacuum,
After carbonization under the conditions shown in Table 1, 5 m shown in Table 1
ol / L potassium hydroxide (KOH) aqueous solution or 5m
It was impregnated with an ol / L zinc chloride (ZnCl ₂ ) aqueous solution for 1 hour.

After drying the water at 50 ° C.,
Activated under the activation condition shown in Table 1, 70 m in length
An activated carbon structure of m, 50 mm in width, and 1 mm was produced.

The specific surface area (BET value) of the solid activated carbon thus obtained was measured by the nitrogen adsorption method.

Furthermore, the pore size distribution was measured from the argon adsorption isotherm by the HK method using Asatsu 2010M manufactured by Shimadzu-Micrometric Co., and the ratio of the volume of the pores having a pore size of 1 nm or less was determined from the mass of the solid activated carbon sample. I asked.

[0063] Also using a Nippon Bunko Raman spectrometer, a solid active carbon was measured by an argon laser beam having a wavelength of 514.5 nm, to obtain a Raman spectrum, 1360 cm for 1580 cm ^-1 vicinity of _G-band (I G) The area ratio of D-band ( _ID ) near ^-1 was determined. The obtained values are shown in Table 1 as the Raman intensity ratio.

On the other hand, 1 mol / mol of tetraethylammonium tetrafluoroborate (Et ₄ NBF ₄ ) using propylene carbonate (PC) as a solvent to 2 sheets of solid activated carbon.
After impregnating L solution as an electrolytic solution, 93 mm x 63 m
m × 0.3 mm laminated with a porous separator made of non-woven glass fiber, 93 mm × 63 m above and below
A m × 0.5 mm aluminum current collector was laminated, and the laminated body was fixed and integrated with an insulating butyl rubber sealing member to produce the electric double layer capacitor of FIG.

Regarding the obtained electric double layer capacitor,
After charging at 2.5V for 30 minutes, 3mA / cm ²
Capacitance per unit mass (F
/ Cm ³ ). Also, 2.5V-30 minutes charge-
The electrostatic capacity (F / cm ³ ) and the rate of change thereof were determined after repeating the constant current discharge of 3 mA / cm ² 100 times, and the results are shown in Table 1.

[0066]

[Table 1]

As is clear from Table 1, after the carbonization treatment, 1
Alkali activation treatment was performed for the second time, and steam activation treatment was performed for the second time, and the specific surface area of the solid activated carbon was 500 m ²
/ G or more and 2500 m ² / g or less, and the pore volume of pores having a diameter of 1 nm or less obtained from an argon adsorption isotherm is 0.35.
~ 0.70 cc / g and 136 in Raman spectroscopy
0 cm ^-1 band (I _D) 1580cm ^-1 band (I _G)
N having an intensity ratio ( _ID / _IG ) of 0.5 or more
o. In all of 2 to 5, 8 to 10, 13 to 15 and 17 to 22, the initial electrostatic capacitance was 18.6 F / cc or more and the deterioration of the electrostatic capacitance after repeated charging and discharging 100 times was 1 as well.
It had excellent properties within 1%.

In particular, the sample No. was subjected to carbonization conditions of 800 to 900 ° C. for 3 hours, the first alkali activation treatment using KOH at a temperature of 800 ° C. for 3 hours, and the second steam treatment at 800 ° C. for 3 hours. ． In 3 and 4, the specific surface area is 200
0~2030m ² / g, a pore volume as a percentage occupied by a pore diameter 1nm or less from 0.58 to 0.62, the Raman intensity 0.8, and the rate of capacitance change -3 to 5% And further improved.

On the other hand, the carbonization temperature is 600 ° C., 120
Sample No. 1, 6, the temperature of alkali activation is 6
Sample No. 7, 11 and sample N whose steam treatment temperature was 600 ° C. and 1100 ° C.
o. Sample Nos. 12 and 16 which were not subjected to the second steam treatment after the carbonization treatment and the first alkali treatment. In 23, any of the specific surface area of activated carbon, the ratio of pore volume and Raman intensity is out of the proper range,
In all cases, the rate of change in capacitance was as large as 18% or more.

[0070]

As described in detail above, according to the solid activated carbon of the present invention and the electric double layer capacitor using the same,
An electric double layer capacitor having a large capacitance and excellent charge / discharge cycle characteristics by controlling the pore size, pore size distribution, and amount of edge faces in the crystal structure of activated carbon that composes a polarizable electrode within a predetermined range. Can be produced.

[0071]

[Brief description of drawings]

FIG. 1 is a schematic sectional view of an electric double layer capacitor of the present invention.

FIG. 2 is a model diagram showing a crystal structure of graphite.

FIG. 3 is an enlarged schematic view of an essential part showing activated carbon particles of the present invention.

[Explanation of symbols]

1 minute polar electrode 11 Solid activated carbon 15 pores

Claims (4)

[Claims] 1. A specific surface area of 500 m ² / g or more and 2500 m ²
/ N or less, diameter of 1n obtained from argon adsorption isotherm
Pore volume of m or less is 0.35 to 0.70 cc / g
The accounting and solid activated carbon strength ratio 1580 cm ^-1 band of 1360 cm ^-1 band in the Raman spectroscopy _{(I D) (I G)} (I D / I G) is characterized in that at least 0.5 . 2. An organic binder is added to (a) a carbonaceous raw material,
Mixing and molding, (b) a step of carbonizing the molded body obtained in the step (a) at 700 ° C. to 1100 ° C. in a reducing atmosphere, and (c) an alkali for the molded body after the carbonization treatment. After impregnating with a metal solution and drying, in a reducing atmosphere,
00 ° C. to 1000 ° C., a step of performing alkali activation treatment for 1 to 10 hours, and (d) 700 ° C. of the molded body after the alkali treatment.
A step of forming a solid activated carbonaceous electrode by steam activation at 1000 ° C to 1000 ° C. 3. An electric double layer capacitor, wherein the solid activated carbon according to claim 1 is used as a polarizable electrode. 4. (e) A step of stacking at least two solid activated carbon electrodes obtained in the above step with a porous separator interposed therebetween, and forming a current collector on the upper and lower surfaces of the stacked body. And (f) a step of impregnating the solid activated carbonaceous electrode with an electrolytic solution, the method for producing an electric double layer capacitor.