JPH11297577A - Electric double-layer capacitor and carbon material used for the capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric double-layer capacitor exhibiting good low- temperature properties and a carbon material used for its electrodes. SOLUTION: An electric double layer capacitor is formed by using a nonaqueous electrolytic solution and polarized electrodes, containing mainly a carbon material for the two poles. In this case, the carbon material is formed by treating a carbon raw material in alkaline. The inter-face distance d002 measured by X-ray diffraction is 0.365 nm or less, and the ratio of surface area to BET measured by nitrogen adsorption method is 0.5 m<2> /g-290 m<2> /g.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric double layer capacitor having excellent charge / discharge characteristics at a low temperature.

[0002]

2. Description of the Related Art At present, an electric double layer capacitor most commonly used is an electric double layer formed at the interface between a polarizable electrode mainly composed of activated carbon (usually a carbonaceous substance having a specific surface area of 300 m ² / g or more) and an electrolyte. It is a condenser using When graphite is used for the electrode, the first time capacity is high, but when it is repeatedly used, the capacity is rapidly reduced, so that it is not used. Such an electric double layer capacitor is an IC
It is used as a backup power source for memories and actuators of LSIs and LSIs, especially in the electronics field. The electric double layer capacitor has a feature that the charge / discharge characteristics at a large current are excellent, the characteristics are not deteriorated even after the charge / discharge of 100,000 to 100,000 times, and the durability is excellent. The operating temperature range is wider than that of secondary batteries such as lithium ion secondary batteries and nickel-metal hydride secondary batteries, and it has a durability temperature characteristic of -30 ° C to + 85 ° C.

Recently, the electric double layer capacitor is considered to be promising as an auxiliary power source for an electric vehicle and a preheater power source for a catalyst muffler for an automobile due to its large current charge / discharge characteristics, durability, and durability temperature characteristics. Is being actively conducted. The electrolyte of the electric double layer capacitor includes
There is an aqueous electrolyte such as an aqueous sulfuric acid solution, and a non-aqueous electrolyte in which a quaternary onium salt or a lithium salt is dissolved in an organic solvent having relatively high conductivity such as propylene carbonate. Among them, the latter non-aqueous electrolyte has a high withstand voltage of about 3 V, and therefore has an advantage that the operating voltage and the energy density per unit cell are large. Therefore, when increasing the capacity of the capacitor, it is more advantageous to use a non-aqueous electrolyte.

[0004] The activated carbon polarizable electrode used in the electric double layer capacitor largely controls the capacity of the capacitor. At present, electric double layer capacitors used as backup power sources for IC memories include activated carbon powder and phenol obtained by carbonizing coconut palm and then activating it in an oxidizing gas atmosphere such as water vapor or carbon dioxide. Activated carbon fiber cloths and the like obtained by carbonizing resin fibers and then activating the same with an oxidizing gas are also used. These activated carbon and activated carbon fiber cloths, in order to increase the interface of the electric double layer,
Each has a high specific surface area of 1500 m ² / g or more. Other activated carbons for polarizable electrodes that exhibit high capacity, such as phenolic resin, furan resin, polyacrylonitrile, polyvinyl chloride resin, petroleum coke, coal pitch and other raw materials activated with steam, potassium hydroxide, etc. And the like, which have many nanometer-sized pores in carbon and have a specific surface area of at least 1000 m ² / g. In addition, in order to reduce the internal resistance of the electric double layer capacitor, a method of heat-treating activated carbon at a high temperature in an inert atmosphere, and using a conductive substance such as fine graphite fiber, conductive carbon black, and stainless steel fiber in the activated carbon powder electrode. A method of adding is known. In an electric double-layer capacitor using a non-aqueous electrolyte such as a propylene carbonate solution of an electric double-layer tetraethylammonium tetrafluoroborate, an effective activated carbon pore diameter capable of expressing a high capacity is determined by the number of molecules of electrolyte ions in the electrolyte. 2 nm to 5 nm considering the diameter
(New Mat. New Processes, 3,352,1985) Also, in Japanese Patent Application Laid-Open No. 9-320906, an easily graphitizable organic material is used as a raw material, and carbonized and activated to such an extent that it is not graphitized. An attempt is being made to achieve both electrical conductivity and surface area.

[0005]

However, most of the measures for increasing the capacity of electric double layer capacitors using activated carbon are based on the premise that the operating temperature is at room temperature around 25 ° C. Although a high capacity is exhibited, at a low temperature around −20 ° C., the voltage drop immediately after the discharge in the electric double layer capacitor becomes remarkably large, and the capacity becomes significantly smaller than that at room temperature. In particular, there is a case where a large current is discharged at a low temperature so that the capacity cannot be substantially expressed. The main factor is a decrease in the mobility of electrolyte ions in the pores of the activated carbon. Hitherto, in order to improve the capacity at low temperatures, it has been proposed to increase the average pore diameter of the activated carbon, to perform a high-temperature heat treatment of the activated carbon, and to reduce the internal resistance by adding a conductive substance to the electrode.

However, these examples were not satisfactory to any extent. Although it is possible to reduce the resistance by increasing the mobility of electrolyte ions at low temperatures by increasing the pore size of activated carbon,
On the other hand, there has been a problem that the capacity of the electric double capacitor at room temperature is significantly reduced due to a decrease in the specific surface area of the activated carbon. Even if the activated carbon is heat-treated at a high temperature, since the activated carbon has a large number of pores, there is little improvement in electrical conductivity due to the development of crystallinity. Even if a conductive substance is added to the electrodes, the conductivity of the activated carbon particles themselves is not so high, so there is a limit to the reduction of the internal resistance of the electric double layer capacitor. There were problems such as a decrease in capacity.

Therefore, in order to enable high-capacity and large-current charging and discharging not only at room temperature but also at low temperature, it is preferable that the conventional activated carbon has as few nanometer-sized pores as possible. However, when the number of pores is small, the specific surface area is extremely small. Therefore, in order to increase the capacity, the capacitance per unit area (F / m ² ) is 10 times that of the conventional activated carbon.
A carbonaceous substance showing 0 times or more is required. Therefore, it can be said that there is substantially no polarizable electrode material of the electric double layer capacitor that satisfies the low-temperature performance strongly required for auxiliary power when starting the electric vehicle in a cold region. Because of this, the temperature dependence of capacitance at room temperature and low temperature is small,
There has been a demand for an electric double layer capacitor having a high capacity at a low temperature.

[0008]

Means for Solving the Invention Accordingly, the present inventors have
As a result of intensive studies to study the above issues,
It is different from the method of adjusting the specific surface area and pore size of charcoal.
As a drastic solution, the capacitance per unit area is
Carbonaceous material significantly larger and lower in specific surface area than conventional activated carbon
By using a substance for a polarizable electrode,
Low temperature dependence of capacity and high capacity at low temperatures
Found that an electric double layer capacitor
The invention has been reached. That is, the object of the present invention is at room temperature.
Electric double layer capable of charging and discharging large current even at low temperature
It is to provide a capacitor, the purpose of which is
Polarizable electrode mainly composed of aqueous electrolyte and carbonaceous material for both electrodes
The carbonaceous material in an electric double layer capacitor using
Obtained by treating carbonaceous raw materials in alkali
And the plane spacing d measured by the X-ray diffraction₀₀₂But 0.365
BET ratio table below nm and measured by nitrogen adsorption method
Area 0.5m^Two/ G or more, 290m^Two/ G or less
And the solute of the non-aqueous electrolyte is R_FourN⁺, R_Four
P⁺(However, R is C_nH_{2n + 1}Alkyl represented by
Group), triethylmethylammonium ion, etc.
Quaternary onium cation and BF_Four ^-, PF₆ ^-, ClO_Four ^-, SbF₆
^-, Or CF_ThreeSO_Three ^-With a salt that combines
And the solute concentration is more than 0.5 mol / l
Less than liters per liter,
You.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
The greatest feature of the present invention is that the polarizable electrode of the electric double layer capacitor is obtained by treating a carbonaceous raw material in an alkali, and the plane distance d _{00 2} measured by X-ray diffraction is 0. .
BET less than 365 nm and measured by nitrogen adsorption method
By using a carbonaceous material having a specific surface area of 0.5 m ² / g or more and 290 m ² / g or less, the capacity per unit area of the carbonaceous material is several hundred times or more as compared with conventional high specific surface area activated carbon. It is extremely large, has a low specific surface area, and has few nm-order pores as compared with conventional high specific surface area activated carbon, so that the electrolyte ions in the pores of the electric double layer capacitor at a low temperature are low. An object is to provide an electric double layer capacitor which has a small IR drop at the time of discharge due to a decrease in mobility and is capable of high capacity and large current charge / discharge not only at room temperature but also at low temperature.

According to the present invention, a carbon material having a relatively high degree of crystallinity is treated in an alkali to have a high capacity per unit area comparable to graphite, and the capacity does not change even after repeated charging and discharging. Not found. The carbonaceous substance used for the polarizable electrode of the electric double layer capacitor of the present invention is preferably obtained by a production method based on the following method. The carbonaceous raw materials before being treated in the alkali of carbonaceous substances include plant-based wood, sawdust, coconut shell,
Pulp waste liquor, fossil fuel coal, petroleum heavy oil, or thermally decomposed coal and petroleum tar and pitch, petroleum coke, coal coke, fiber spun from tar pitch, carbon fiber, natural graphite, artificial graphite , Carbon black, fine graphite fiber, carbon aerogel, activated carbon,
Synthetic polymer, phenolic resin, furan resin, polyvinyl chloride resin, polyvinylidene chloride resin, polyimide resin,
Polyamide resins, liquid crystal polymers, plastic waste, waste tires, and many other types are used, but graphitizable carbon or graphitizable organic compounds that can be easily graphitized are preferred. As such graphitizable organic compounds and carbon, polycyclic aromatic ring compounds such as coal and petroleum such as tar, pitch, mesophase, polyimide resin, etc., aliphatic compounds such as polyvinyl chloride resin, polyvinylidene chloride Resins. In particular, the carbonaceous and graphite raw materials for petroleum and coal, such as petroleum coke, coal coke, fluid coke, anthracite, and mesocarbon microbeads, which are easily graphitizable carbon, are basically developed at low cost and crystallinity. Is preferred. These carbonaceous materials can be used as they are or by further developing the crystallinity by carbonization treatment to obtain carbonaceous materials of the present invention before being treated in an alkali.

The alkali used for the treatment in the alkali of the present invention is not particularly limited.
Caustic alkali such as OH, NaOH, K ₂ CO ₃ , Na
Alkali carbonate such as ₂ CO ₃ can be used, preferably caustic, especially KOH. The alkali can be used as a melt, an aqueous solution or an organic solvent solution, but is preferably used as a melt or a high-concentration aqueous solution. Graphite, graphitized mesophase,
Carbonaceous materials such as carbon fibers, micrographite fibers, petroleum coke, coal coke, etc., which have been heat treated at a high temperature of 900 ° C. or higher, need not be further carbonized, but other organic or carbonaceous materials The substance is preferably carbonized at a temperature of 900 ° C. or higher in an inert atmosphere. In addition, in order to sufficiently develop crystallinity, 1300 ° C.
It is more preferable to perform the carbonization treatment at the above high temperature.

When a non-graphitizable organic compound such as a phenolic resin or a furan resin is used, it is necessary to optimize the curing conditions and carbonize at 1400 ° C. or more to sufficiently develop the crystallinity. Thus, the carbonaceous raw material of the present invention can be obtained. The interplanar spacing d ₀₀₂ measured by X-ray diffraction of these crystalline carbonaceous materials is 0.363 n
m and the size Lc in the c-axis direction of the crystal grains is preferably 2 nm or more. As the shape of the carbonaceous material, there are various shapes such as crushing, granulation, granule, fiber, felt, woven fabric, and sheet shape, and any of them can be used in the present invention.

The most preferred embodiment used in the present invention is a method of heat-treating a carbonaceous raw material in molten KOH. The carbonaceous raw material / KOH is mixed at a weight ratio of 1 to 8, and nitrogen gas and argon are mixed. In an inert gas such as gas, 60
The temperature is maintained at 0 ° C. to 950 ° C., preferably 650 ° C. to 850 ° C., and the holding time is 10 minutes to 5 hours, preferably 30 minutes to 3 hours. After the heat treatment, the carbonaceous material of the present invention is preferably obtained by washing with water to remove potassium, and then drying. The plane distance d ₀₀₂ measured by X-ray diffraction of the obtained carbonaceous material is 0.365 nm or less, and the BET specific surface area measured by the nitrogen adsorption method is 0.5 m ² / g or more.
It is preferably 90 m ² / g or less. The obtained carbonaceous material is subjected to a temperature of 500 to 2500 ° C., preferably 700 to 1500 under an inert atmosphere of nitrogen, argon, helium, xenon or the like.
Heat treatment may be performed at a temperature of 0 ° C. to remove unnecessary surface functional groups or to improve the crystallinity of carbon to increase electron conductivity. When the carbonaceous material is granular, the average particle size is preferably 30 μm or less from the viewpoint of improving the bulk density of the electrode and reducing the internal resistance.

A polarizable electrode mainly composed of a carbonaceous substance is composed of a carbonaceous substance and a binder. Further, a conductive substance may be further added to impart conductivity to the electrode. The polarizable electrode can be formed by a conventionally known method. For example, it can be obtained by adding and mixing polytetrafluoroethylene to a mixture of a carbonaceous substance and acetylene black, followed by press molding. Alternatively, after adding and mixing coal pitch having a relatively high softening point as a binder, the molded product may be fired in an inert atmosphere to a temperature not lower than the thermal decomposition temperature of the binder to obtain a molded product. Furthermore, it is also possible to obtain a polarizable electrode by sintering only activated carbon without using a conductive agent and a binder.
The electrode may be any of a thin coating film, a sheet-like or plate-like molded body, and a plate-like molded body made of a composite.

As the conductive agent used for the polarizable electrode,
Acetylene black, carbon black such as Ketjen black, natural graphite, thermally expanded graphite, carbon fiber, ruthenium oxide, titanium oxide, aluminum, at least one conductive agent selected from the group consisting of metal fibers such as nickel is preferable, in a small amount Acetylene black and Ketjen black are particularly preferable in that the conductivity is effectively improved. The amount of the activated carbon varies depending on the bulk density of the activated carbon. However, if the amount is too large, the proportion of the activated carbon is reduced and the capacity is reduced. As the binder, polytetrafluoroethylene, polyvinylidene fluoride, carboxymethyl cellulose, fluoroolefin copolymer crosslinked polymer,
Polyvinyl alcohol, polyacrylic acid, polyimide,
It is preferable to use at least one or more of petroleum pitch, coal pitch, and phenol resin.

In the present invention, in order to increase the capacity of the electric double layer capacitor at room temperature, the specific surface area is set at 300.
Activated carbon of not less than m ² / g and not more than 2800 m ² / g, preferably a KOH-activated product made from phenolic resin pyrolysis products, petroleum coke, etc., which exhibits low capacity at low temperature but high capacity at room temperature Activated carbon powder having a surface area of 1000 m ² / g or more is added to the carbonaceous material of the present invention in an amount of 10% by weight to 7% by weight.
It may be molded by adding about 0% by weight. Further, by adjusting the natural potential of the electrode in the non-aqueous electrolyte solution to around 1.3 V to 2.5 V by a method such as electrochemically doping a small amount of lithium ions into the obtained polarizable electrode, The withstand voltage of the double layer capacitor, the durability when a voltage is applied for a long time, and the charge / discharge durability are improved. These electric double layer capacitors in which the natural potential of the polarizable electrode is arbitrarily adjusted are also included in the present invention.

The current collector is electrochemically and chemically resistant to corrosion.
There is no particular limitation, but for example, positive
At the poles are stainless steel, aluminum, titanium and tantalum
Yes, for the negative electrode, stainless steel, nickel, copper, etc.
used. The electrolyte is preferably a non-aqueous electrolyte. Non-aqueous
The solute of the electrolyte is R_FourN⁺, R_FourP ⁺(However, R is C
_nH_{2n + 1}), Triethylmethyla
A quaternary onium cation such as ammonium ion,
BF_Four ^-, PF₆ ^-, ClO_Four ^-, SbF₆ ^-Or CF_ThreeSO_Three ^-Become
Salt combined with Nion or cation is Lithium
A lithium salt which is a mu ion is used. The lithium salt is L
iBF_Four, LiClO _Four, LiPF₆, LiSbF₆,
LiAsF₆, LiCF_ThreeSO_Three, LiC (CF_ThreeSO
_Two)_Three, LiB (C₆H_Five)_Four, LiC_FourF₉SO_Three,
LiC₈F₁₇SO_Three, LiB (C₆H_Five)_Four, LiN
(CF_ThreeSO_Two)_TwoOne or more substances selected from
New In particular, electrical conductivity, stability, and low cost
From the point that the cation is R_FourN⁺(However, R is C_nH
_{2n + 1}An alkyl group represented by
If the ammonium ion or anion is BF_Four ^-, PF₆ ^-, ClO_Four
^-, And SbF₆ ^-Are preferred.

The solute concentration in these non-aqueous electrolytes is adjusted to a value of 0.1 so that the characteristics of the electric double layer capacitor can be sufficiently obtained.
The concentration is preferably from 5 to 2 mol / l, and particularly preferably at a concentration of from 0.7 mol / l to 1.9 mol / l, high electric conductivity is obtained. In particular, when charging and discharging at a low temperature of −20 ° C. or less, if the concentration exceeds 2 mol / liter, the electric conductivity of the electrolytic solution decreases, which is not preferable. Also,
If the amount is less than 0.5 mol / liter, the electric conductivity is unfavorably low at both room temperature and low temperature.

Although the solvent of the non-aqueous electrolyte is not particularly limited, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate,
Methyl ethyl carbonate, diethyl carbonate, sulfolane, methyl sulfolane, γ-butyrolactone, γ
-An organic solvent comprising at least one selected from valerolactone, N-methyloxazolidinone, dimethylsulfoxide, and trimethylsulfoxide is preferred. At least one selected from propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, sulfolane, methyl sulfolane, and γ-butyrolactone from the viewpoint of excellent electrochemical and chemical stability and electric conductivity. Is especially preferred. However, a high melting point solvent such as ethylene carbonate alone cannot be used because it becomes a solid at a low temperature and must be a mixed solvent with a low melting point solvent such as propylene carbonate. The water content in the non-aqueous electrolyte is preferably 200 ppm or less, more preferably 50 ppm or less, so as to obtain a high withstand voltage.

[0020]

EXAMPLES Hereinafter, the present invention will be described with reference to specific examples, but the present invention is not limited to the following examples. (Example 1) Coal tar pitch from which a quinoline-insoluble component was removed was coked with a delayed coker, heat-treated at about 1500 ° C. for 4 hours in a rotary kiln, and then pulverized with a ball mill to have an average particle size of about 20 μm. Was obtained. After adding twice the weight ratio of granular potassium hydroxide to the mixture and mixing, the mixture was placed in a nickel crucible and heat-treated at 800 ° C. for 2 hours in a nitrogen stream. After cooling, washing with water and neutralization with a 1N-hydrochloric acid aqueous solution were repeated to remove the potassium component, followed by drying at 115 ° C. to obtain a carbonaceous powder. FIG. 1 shows an X-ray diffraction pattern of the obtained carbonaceous powder. The interplanar spacing d ₀₀₂ determined from this X-ray diffraction pattern was 0.3454 nm. In addition, a nitrogen adsorption measurement device (Carlo Elba's Soapmatic 1600)
The BET specific surface area of the carbonaceous substance measured by 1 m ² /
g.

Next, 80% by weight of carbonaceous material, 10% by weight of acetylene black, 10% by weight of polytetrafluoroethylene
After kneading the mixture consisting of, using a tablet press made by JASCO Corporation, press molding with a hydraulic press at a pressure of 50 kgf / cm ^{2 to} a diameter of 10.5 mm and a thickness of 0.5 mm to obtain a disc-shaped molded body Two sheets were produced. In a vacuum of 0.1 torr or less,
After drying at 300 ° C. for 3 hours, it was transferred into a glove box under a nitrogen atmosphere. Two molded bodies were impregnated with propylene carbonate and ethylene carbonate (volume ratio 1 + 1) containing triethylmethylammonium tetrafluoroborate at a concentration of 1.3 mol / liter. Next, the two molded bodies were used as a positive electrode and a negative electrode, respectively, and a polyethylene separator was arranged between the two electrodes to assemble a coin type cell as shown in FIG. 3 to obtain an electric double layer capacitor.

(Example 2) Coal tar pitch from which quinoline insoluble components were removed was coked with a delayed coker, heat-treated at 950 ° C for 4 hours in a rotary kiln, and then pulverized to obtain a carbonaceous raw material. Example 1
An electric double layer capacitor similar to the above was constructed. The interplanar spacing d ₀₀₂ of the obtained carbonaceous powder was 0.3605 nm, and BE
The T specific surface area was 11 m ² / g.

Example 3 Example 1 was the same as Example 2 except that the weight ratio of potassium hydroxide was 3 times.
An electric double layer capacitor similar to the above was constructed. The interplanar spacing d ₀₀₂ of the obtained carbonaceous powder was 0.3615 nm, and BE
The T specific surface area was 17 m ² / g.

(Example 4) Petroleum pitch was set to 4 at 1400 ° C.
An electric double layer capacitor was formed in the same manner as in Example 1 except that heat treatment was performed for a time and pulverization was performed to obtain a carbonaceous raw material. The interplanar spacing d ₀₀₂ determined from the X-ray diffraction pattern of the carbonaceous powder obtained by heat treatment in molten KOH was 0.3458 nm. The BET specific surface area of the carbonaceous material is 1 m ²
/ G.

(Comparative Example 1) A phenol resin (novolak resin) was heat-treated at 700 ° C. for 4 hours in a nitrogen stream.
An electric double layer capacitor was constructed in the same manner as in Example 1 except that pulverization was performed to obtain a carbonaceous raw material. FIG. 2 shows an XRD pattern of the obtained carbonaceous powder (activated carbon). It could not be clearly detected a peak derived from the surface spacing d _002, as seen in Examples 1-4. Further, the BET specific surface area was 1980 m ² / g, and the average pore diameter was about 18 °.

Comparative Example 2 Coal pitch obtained by heat-treating a coal tar pitch from which a quinoline-soluble component was removed at 500 ° C. for 4 hours in a rotary kiln was pulverized as it was into 2.3 times granular material. After potassium hydroxide was added and mixed, the mixture was placed in a nickel crucible and placed in a nitrogen stream at 65 ° C.
Heat treatment was performed at 0 ° C. for 1 hour. After cooling, washing with water and neutralization with hydrochloric acid were repeated, and an electric double layer capacitor was formed in the same manner as in Example 1 except that heat treatment was performed at 1000 ° C. for 1 hour in a nitrogen stream to obtain a carbonaceous powder. The interplanar spacing d ₀₀₂ of the obtained carbonaceous powder is 0.375 nm, and the BET specific surface area is
It was 2200 m ² / g.

Comparative Example 3 Activated carbon powder (specific surface area: 162) obtained by activating coal pitch under steam at about 1000 ° C.
(0 m ² / g, interplanar spacing d ₀₀₂ : 0.370 nm, average particle size: about 20 μm, purity: 99.5% or more) except that a carbonaceous substance was used, and the same electric double layer capacitor as in Example 1 was constructed. did. The electric double-layer capacitors of Examples 1 to 4 and Comparative Examples 1 to 3 were obtained by using a commercially available charging / discharging device at -2.
3.8 V or 2.8 at 5 ° C. or 25 ° C.
8.65 mA (10.0 mA) after applying a voltage of V for 1 hour.
The battery was discharged to 1.0 V at a constant current of mA / cm ² ) to determine the capacitance of the electric double layer capacitor. Table 1 shows the measurement results of the capacitance.

[0028]

[Table 1]

[0029]

According to the present invention, an electric double layer capacitor having excellent low temperature characteristics can be obtained.

[Brief description of the drawings]

FIG. 1 is a view for explaining an X-ray pattern of a carbonaceous substance of Example 1.

FIG. 2 is a diagram illustrating an X-ray pattern of activated carbon.

FIG. 3 is an explanatory diagram of a coin-type cell used in an example of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Case of stainless steel container 2 Positive electrode 3 Gasket 4 Separator 5 Negative electrode 6 Top cover of stainless steel container

Continued on the front page (72) Inventor Mitsuo Suzuki 1000 Kamoshita-cho, Aoba-ku, Yokohama-shi, Kanagawa Prefecture Inside Mitsubishi Chemical Research Institute (72) Inventor Megumi Aizawa 1000 Kamoshida-cho, Aoba-ku, Yokohama-shi, Kanagawa Prefecture Mitsubishi Chemical Corporation Inside Yokohama Research Institute

Claims (10)

[Claims] 1. An electric double layer capacitor using a non-aqueous electrolyte and a polarizable electrode mainly composed of a carbonaceous substance in both electrodes, wherein the carbonaceous substance is obtained by contacting a carbonaceous raw material with an alkali. Plane spacing d measured by X-ray diffraction
₀₀₂ is 0.365 nm or less, and the BET specific surface area measured by the nitrogen adsorption method is 0.5 m ² / g or more and 290
An electric double layer capacitor having a m ² / g or less. 2. The electric double layer capacitor according to claim 1, wherein the contact treatment with an alkali is a method of contacting with a molten solution of caustic alkali. 3. The method according to claim 1, wherein the solute of the electrolytic solution is R ₄ N ⁺ , R ₄ P ⁺
(Where R is an alkyl group represented by C _n H _{2n + 1} ) and at least one quaternary onium cation selected from the group consisting of triethylmethylammonium ions;
^{_{4 -, PF 6 -, ClO}} 4 -, SbF 6 - and CF ₃ SO ₃ ^- is at least one anion and the combined salt selected from the group consisting of, and solute concentration, 0.5 mol / l The electric double layer capacitor according to claim 1, which is a non-aqueous electrolyte having a concentration of 2 mol / liter or less. 4. The electric double layer capacitor according to claim 1, wherein the carbonaceous material of the carbonaceous substance has been subjected to a pre-heat treatment at 900 ° C. or higher. 5. The electric double layer capacitor according to claim 1, wherein the carbonaceous raw material is graphitizable carbon. 6. The electric double layer according to claim 1, wherein the polarizable electrode contains activated carbon powder having a specific surface area of 300 m ² / g or more and 2800 m ² / g or less in addition to the carbonaceous material. Capacitor. 7. The electric double layer capacitor according to claim 1, wherein the electric double layer capacitor is used in a temperature range of −20 ° C. or lower. 8. A carbonaceous raw material is treated in an alkali, and its plane distance d ₀₀₂ measured by X-ray diffraction is 0.365 nm.
A carbonaceous material for an electrode of an electric double layer capacitor, wherein the carbonaceous material has a BET specific surface area of 0.5 m ² / g or more and 290 m ² / g or less as measured by a nitrogen adsorption method. 9. The carbonaceous material for an electrode of an electric double layer capacitor according to claim 8, wherein the carbonaceous material of the carbonaceous material has been pre-heat treated at 900 ° C. or higher. 10. The carbonaceous material for an electrode of an electric double layer capacitor according to claim 8, wherein the carbonaceous material is graphitizable carbon.