WO2008053919A1

WO2008053919A1 - Activated carbon and process for production thereof, nonaqueous type polarizable electrodes and electric double-layer capacitors

Info

Publication number: WO2008053919A1
Application number: PCT/JP2007/071215
Authority: WO
Inventors: Shuichi Ishida; Hisahito Takenaka; Shushi Nishimura; Yoshifumi Egawa; Kiyoto Otsuka
Original assignee: Kuraray Chemical Co., Ltd
Priority date: 2006-11-02
Filing date: 2007-10-31
Publication date: 2008-05-08
Also published as: JPWO2008053919A1; JP5168585B2

Abstract

The invention aims at providing a nonaqueous type polarizable electrode which little suffers from gas generation and has high capacitance by using an inexpensive activated carbon made from coconut shells. The aim is attained by an activated carbon which is prepared from coconut shells through carbonization and steam activation and which contains surface functional groups in a total content of 0.4meq/g or below with the provisos that the surface functional groups are free from carboxyl groups and lactone groups and that quinone groups account for at least 50% of all the surface functional groups and has an alkali metal content of 50 to 500ppm, a chloride ion concentration of 0.1 to 20ppm and a BET specific surface area of 1500 to 2000m2/g; and a process for the production of the activated carbon.

Description

Specification

Activated carbon and method for producing the same, non-aqueous polarizable electrode and electric double layer canister

Technical field

The present invention relates to activated carbon and a method for producing the same, and a non-aqueous polarizable electrode and an electric double layer capacitor. When the activated carbon of the present invention is produced on a polarizable electrode and used in an electric double layer capacitor, the non-aqueous polarizable electrode made of the activated charcoal of the present invention has a high capacitance and generates a small amount of gas. It is preferably used for a durable electric double layer capacitor.

Background art

[0002] Electric double layer capacitors are superior in output characteristics and life characteristics compared to batteries. Taking advantage of these characteristics, backup of various memories, power assists for cars and trains, road leveling and rush It has been developed for many applications such as current and storage power sources such as UPS, and some have been put into practical use. However, the performance required as an electric double layer capacitor has become severe in recent years, and further improvement in the high capacitance per polarizable electrode volume and durability is desired.

[0003] The durability of a capacitor is greatly affected by impurities in activated carbon as a raw material, and therefore activated carbon is required to have as few impurities as possible (Patent Document 1 and Patent Document 2). Activated charcoal is usually refined by treatment with acids such as hydrochloric acid and water washing, and the ability to remove metal impurities by such treatment. In the water washing treatment, acids such as hydrochloric acid tend to remain on the activated carbon. It was very difficult to obtain a polarizable electrode made of activated charcoal that exhibits high capacitance and durability.

Patent Document 1: Japanese Patent Laid-Open No. 1 241811

Patent Document 2: Japanese Patent Laid-Open No. 2001-284188

[0004] On the other hand, manufacture of a polarizable electrode in which carbon fiber or activated carbon fiber is heat-treated at 900 ° C to 2000 ° C in vacuum, inert gas, or V in a reducing gas atmosphere Method (Patent Document 3) and electric double layer capacities that are heat-treated at 1300 ° C in an inert gas atmosphere A method for producing shita (Patent Document 4) is known. According to these methods, the amount of surface functional groups is reduced, and further, crystallites grow by high-temperature heat treatment in an inert atmosphere, and the activated carbon is gradually transferred to a regular graphite structure. It is possible to increase the conductivity of

Patent Document 3: Japanese Patent Laid-Open No. 60-189162

Patent Document 4: Japanese Patent Laid-Open No. 2000-299259

[0005] However, in activated carbon, the temperature at which the crystal structure grows varies depending on the raw material, the temperature at which the crystal structure grows also varies depending on the impurity content, and further, depending on the type of surface functional group, it can be easily decomposed. There are some that react easily with the electrolyte and some that do not. However, these publications teach the temperature at which the crystal structure grows and how much surface functional groups should be reduced! ! /

[0006] O / C before heat treatment: When activated carbon of 0.061 is heated at a temperature of 500 to 1100 ° C under a nitrogen stream to obtain activated carbon having an O / C of 0.055 or less, the battery is charged. It has been reported that the irreversible capacity associated with the discharge is reduced, which makes it possible to provide an electrode for an electric double layer capacitor that is advantageous for maintaining the discharge capacity when charging and discharging are repeated (Patent Document 5). ). However, Patent Document 5 states that the ratio of oxygen atom / carbon atom is as small as possible! /, Is preferred! / !, an impurity that affects durability and leakage current! / No matter what you mention! /!

Patent Document 5: JP-A-10-116755

[0007] In addition, activated carbons defined by the amount of at least one surface functional group selected from the group of carboxyl group, quinone group, hydroxyl group, and rataton group are also known, and are suitable for highly polarizable electrodes having high strength. It is described that it is a material (Patent Document 6). However, Patent Document 6 describes force impurities described in the total amount of surface functional groups that should be used as polarizable electrodes! /.

Patent Document 6: Japanese Unexamined Patent Publication No. 2000-169129

[0008] In addition, activated carbon for electric double layer capacitors having an oxygen content of 1 mg or more and 20 mg or less per lg of activated carbon, and a natural potential of 2.85 V or more and 3.03 V or less at the counter electrode lithium in the non-aqueous electrolyte. (Patent Document 6) has been proposed. According to this activated carbon, nature By making the potential within the above range, it becomes possible to suppress the polarization potential of the activated carbon electrode below the oxidative decomposition potential of the electrolyte, and as a result, it is possible to improve the durability of the electric double layer capacitor. It is expected to obtain a double layer capacitor.

Patent Document 7: Japanese Patent Laid-Open No. 2002-33249

Disclosure of the invention

Problems to be solved by the invention

[0009] In Patent Document 7, the activated coconut husk activated carbon is heat-treated in an inert gas atmosphere to remove unnecessary surface functional groups, or the carbon crystallinity is developed to increase conductivity. Good power S is described, and it is also described that metal impurities, ash, etc. contained in carbon are removed by washing in an acid aqueous solution such as hydrochloric acid, nitric acid, and sulfuric acid. However, sulfuric acid and nitric acid cannot remove impurities sufficiently, but strongly oxidize the carbon, resulting in an unnecessary increase in surface functional groups. On the other hand, when washed with hydrochloric acid, it is possible to remove impurities S, chloride ions adsorb on activated carbon, and it is extremely difficult to remove.

[0010] In addition to being required to have a high capacitance, the electric double layer capacitor has recently been required to produce a small amount of gas especially in terms of safety! /. In order to produce an electric double layer capacitor that satisfies these requirements, the overall surface functional groups, alkali metal content, specific surface area, etc. should be comprehensively studied. Absent. Therefore, a first object of the present invention is to provide activated carbon suitable as a non-aqueous polarizable electrode for an electric double layer capacitor having a high capacitance and a small amount of gas generation.

[0011] A second object of the present invention is to provide a production method capable of efficiently reducing chlorine ions remaining by acid cleaning, and a third object of the present invention is from the activated carbon. An object of the present invention is to provide a non-aqueous polarizable electrode having a high electrostatic capacity. The fourth object of the present invention is to provide an electric double layer capacitor using such a polarizable electrode. Means for Solving the Problems

[0012] The inventors of the present invention have made extensive studies and studied the concentration of all surface functional groups, alkali metals, and chloride ions. The inventors have found that the above object can be achieved by a specific activated carbon specified by the BET specific surface area and have reached the present invention. That is, the present invention is a coconut husk activated carbon obtained by carbonizing coconut husk and steam activation, has a total surface functional group of 0.4 meq / g or less, contains 50 to 500 ppm of alkali metals, and contains chlorine. An activated carbon having an ion concentration of 0.1 ppm to 20 ppm and a BET specific surface area of 1500 to 2000 m ² / g.

[0013] Further, another invention of the present invention is the production of activated carbon characterized in that steam activated activated coconut shell activated carbon is washed with hydrochloric acid and then deoxidized in an oxidizing gas atmosphere at 500 to 1000 ° C. It is a method.

[0014] Still another invention of the present invention is a non-aqueous polarizable electrode made of such activated carbon. Yet another invention of the present invention is an electric double layer capacitor using such a polarizable electrode.

The invention's effect

[0015] By producing the activated carbon of the present invention as a polarizable electrode and using it in a non-aqueous electric double layer capacitor, it is possible to construct an electric double layer capacitor having a high capacitance and a small amount of gas generation. . Such an electric double layer capacitor is useful as an electric double layer capacitor having excellent durability.

BEST MODE FOR CARRYING OUT THE INVENTION

The activated carbon of the present invention is obtained by carbonizing coconut shells and activating water vapor. Known carbonization conditions can be adopted. For example, carbonization is performed by heating and distillation at 400 ° C to 600 ° C. Further, as an activation method, water vapor activation is adopted in the present invention from the viewpoint of electrode corrosiveness when an electric double layer capacitor is formed, a point that surface functional groups are small, and gas generation is suppressed.

In the activated carbon of the present invention, the total surface functional group is preferably 0.4 meq / g or less, and more preferably 0.3 meq / g or less. The surface functional groups include carboxyl group, rataton group, hydroxyl group, and quinone group. The carboxyl group and latataton group, which are easily decomposed at high voltage, must not contain the quinone group. It must be at least%. The quinone group is preferably 60% or more of the total surface functional groups. This This is because gas generation is suppressed when there are more quinone groups that do not contribute much to decomposition or reaction with the electrolyte than hydroxyl groups.

[0018] Since alkali metals affect durability, the activated carbon of the present invention needs to be 500 ppm or less. Alkali metals are a general term for the 6 elements belonging to Group IA of the Periodic Table. The metal components and content of raw coconut husk vary depending on the place of production, but sodium and potassium are contained in the range of several hundred ppm to several thousand ppm, and such sodium and cadmium correspond to the alkali metals described above. .

[0019] If too much alkali metal affects the durability, it is preferable to reduce it as much as possible. However, in order to achieve Oppm, it is necessary to repeat washing extremely, and the balance between economic efficiency and performance is also In the activated carbon of the present invention, the range is 50 ppm to 500 ppm. 100 ppm to 400 ppm is preferred. Raw coconut husks contain tens of ppm of transition metals such as iron, chromium, copper, and zinc in addition to alkali metals, and are concentrated in the activated carbonization process and may be present in the activated carbon at several hundred ppm. is there. Since transition metals also affect the durability, it is preferable to use as little as possible! /, But 50 ppm or less is preferable and 20 ppm or less is more preferable from the balance of economy and performance. These transition metals, like alkali metals, are removed by washing.

[0020] As a method for removing impurities, cleaning with an inorganic acid is preferable, but cleaning with hydrochloric acid that does not oxidize activated carbon is more preferable. The activated carbon may be washed with hydrochloric acid and then washed with water, or a combination of washing with water and pickling may be used as appropriate, such as repeated washing and washing. The concentration of hydrochloric acid is preferably 0.1% to 3.0%, more preferably 0.3% to 1.0%. If the hydrochloric acid concentration is low, it is necessary to increase the number of pickling operations to remove impurities. The pickling and rinsing temperatures are usually higher than 80 ° C. Since the remaining hydrochloric acid corrodes the electrode, the activated carbon of the present invention has a chlorine ion concentration of 0.1 ppm to 20 ppm. 0.1 ppm to 5 ppm is preferable, and 0.1 ppm to 3 ppm is more preferable. Chlorine ion concentration can be measured by the extraction method.

[0021] If the BET specific surface area of the activated carbon is too small, the average pore diameter also becomes relatively small, and the resistance that seems to be due to the diffusion resistance of the nonaqueous electrolyte ions in the pores during charge / discharge under a large current increases. If it is too large, the bulk density of the activated carbon will decrease and the unit volume will Therefore, the activated carbon of the present invention is 1500 to 2000 m ² / g.

[0022] The coconut husk activated carbon carbonizes coconut husk, activates steam, and can be obtained through steps such as acid washing and water washing. Since activated carbon usually contains hydrochloric acid, In order to remove the remaining hydrochloric acid more efficiently and reliably, it is preferable to remove the remaining hydrochloric acid with an activation reaction by contacting with an oxidizing gas for a short time after washing with hydrochloric acid. That is, the activated carbon of the present invention is preferably produced by washing steam activated coconut husk activated charcoal with hydrochloric acid and then deoxidizing it in an oxidizing gas atmosphere of 500 to 1000 ° C. Examples of the oxidizing gas include oxygen, water vapor, carbon dioxide gas, and combustion gas obtained by burning kerosene filling pan. These oxidizing gases may be used as a mixture or may be diluted with an inert gas. Of these, a combustion gas obtained by burning kerosene or propane, or a gas obtained by adding steam to the combustion gas is more preferable because it can be used as a heat source.

[0023] When the treatment temperature for contacting with the oxidizing gas is too low, the activation reaction does not proceed sufficiently, and when it is too high, the activation reaction proceeds rapidly, and the pore structure strength change adjusted with great effort is obtained. In order to hesitate, it is preferable that the temperature is 500 to 1000 ° C, and more preferable that the temperature is 650 to 850 ° C. The time of contact with the oxidizing gas varies depending on the temperature. Usually, it is about 30 minutes to 3 hours. The oxidizing gas concentration varies depending on the gas used. It is usually 1% to 40% when steam is added, and 2% or more is preferred when carbon dioxide is added.

[0024] Oxidation and thermal history during washing are low! / Activated carbon may have a little more surface functional groups! / In such cases, deoxidized activated carbon may be used as a rare gas or nitrogen gas. Heat treatment is further performed at 900 to 1200 ° C under an inert gas atmosphere. When heat treatment is performed in a state where there are many impurities, crystallites are more likely to grow, but pore shrinkage occurs and the pore diameter tends to change immediately.After adjusting the amount of impurities by acid washing and deoxidation treatment, Heat treatment can reduce the surface functional groups as pore shrinkage occurs. If the heat treatment temperature is less than this range, the surface functional groups do not decompose, and if it is too large, the surface functional groups decompose, but the pores of the activated charcoal shrink and a sufficient capacity cannot be obtained. In addition, heat treatment in an inert gas atmosphere develops a six-membered ring structure and increases the conductivity of activated carbon. [0025] As the furnace for heat treatment and deoxidation treatment, various types of furnaces such as a rotary kiln, fluidized bed furnace, fixed bed furnace, moving bed furnace, moving bed furnace, etc. can be used. This can be applied to both continuous and intermittent furnaces. As a heating means, any electric heating, gas combustion type heating, high frequency induction heating, electric heating, etc. can be applied as long as it can heat up to a predetermined temperature. These heating means may be used alone or in combination.

[0026] When a non-aqueous polarizable electrode is produced using the activated carbon of the present invention, the activated carbon is used after being pulverized. As the particle size of the activated carbon, a force center particle size of 2 111 to 30 111 depending on the method for producing the electrode is preferable. When the central particle diameter is within this range, it is preferable from the viewpoint of improving the bulk density of the electrode and internal resistance immediately after the electrode is produced. As a pulverization method, a known pulverizer such as a cone crusher, a duff, a Norre-no-re crusher, a tisk crusher, a rotary crusher, a Norre mill, a centrifugal roll mill, a ring-Rhino reminole, a centrifugal ball mill or the like can be used. Further, the particle size distribution may be controlled using a classifier. Furthermore, it is desirable to carry out in an inert gas atmosphere in order to prevent the surface from being oxidized during grinding.

[0027] The activated carbon of the present invention is preferably used as a material for a non-aqueous polarizable electrode of an electric double layer capacitor. In order to manufacture a polarizable electrode, a known method may be employed. For example, the activated carbon of the present invention can be produced by adding a binder and a conductive material, kneading and rolling. As the binder, polytetrafluoroethylene, polyvinylidene fluoride, carboxymethyl cellulose, polybutyl alcohol, polyacrylic acid and the like can be used. The amount of the binder used is preferably as small as possible, but about 0.5 wt% to 10 wt% can be added in view of the strength of the electrode.

[0028] As the conductive material, conductive carbon black such as acetylene black and ketjen black, natural graphite, artificial graphite, thermally expanded graphite, carbon fiber, ruthenium oxide, titanium oxide, aluminum, nickel and other metal fibers, metal Examples thereof include fine particles. These can be used alone or in combination. Among these, the amount of conductive carbon black that is effective in a small amount is particularly preferred because the ratio of activated carbon decreases when the amount of activated carbon is too large, depending on the bulk density of the activated carbon. Is about 5% to 15%. [0029] Further, when the binder and the conductive material are kneaded with the activated carbon, if necessary, an organic compound such as alcohol or N-methylpyrrolidone, a solvent such as water, a dispersant, or various additives may be added. Good. When a solvent is added, the kneaded product can be easily used as a coating agent, and the kneaded product can be easily applied to a current collector to form a coated electrode.

[0030] In addition, it is possible to apply heat at the time of kneading. When the temperature is higher than necessary, the bonding material melts due to the deterioration of the used binder component, and the pores of the activated carbon may be blocked. Therefore, it is necessary to consider temperature conditions depending on the binder. Usually, it is preferable to mix it so that it does not exceed 300 ° C.

[0031] The solvent of the non-aqueous electrolyte solution used for the electric double layer capacitor is not particularly limited, but propylene carbonate, ethylene carbonate, butylene carbonate, dimethylolene carbonate, methinorenoate carbonate, Powers such as jetinole carbonates-Bonates, y Butyrolatatones, α-methinolate _Ί butyllatatanes, β-methinolate γ-butyllactone, γ-valerolatatanes, 3-methyl-1-γ-valerolatatanes and other lactones, acetonitrile, propionitrile, etc. Sulphoxides such as nitriles, dimethyl sulfoxide and jetyl sulfoxide, amides such as dimethylformamide and jetylformamide, ethers such as tetrahydrofuran and dimethoxyethane, dimethylsulfola , The organic solvent preferably comprises one or more selected from sulfolane. However, when a high melting point solvent such as ethylene carbonate is used, it is necessary to use a mixed solvent with a low melting point solvent such as propylene carbonate in consideration of use at a low temperature. In addition, the water content in the non-aqueous electrolyte is preferably as low as possible in consideration of decomposition at high voltage, and is usually 200 ppm or less, more preferably 50 ppm or less.

[0032] The electrolyte to be dissolved in these solvents is not particularly limited, but those that dissolve in a solvent at a high concentration are preferable because the electric double layer capacity is sufficiently exhibited. In general, quaternary ammonium cations such as trimethylethylammonium ion are spiro-type cations such as spiro (1, 1 ')-bipyrrolidinium ion and tetrafluoroboric acid. A salt in combination with anion, hexafluorophosphate anion, perchlorate anion, bistrifluoromethanesulfonimide anion, or the like, or a lithium salt whose cation is a lithium ion is used. In addition, 1-methyl 3-methylimidazolium tetrafluorovolley In the case of using an ionic liquid such as a salt, there is no upper limit of the concentration unless it solidifies within the temperature range to be used.

[0033] In the electric double layer capacitor having a pair of electrodes and the non-aqueous electrolyte solution, an electric double layer capacitor excellent in capacitance and durability can be obtained by the configuration in which the positive electrode includes the activated carbon of the present invention. From the viewpoint of achieving both the electrostatic capacity S and the durability at a higher level, which is possible, it is preferable that the activated carbon of the present invention is included in both of the pair of electrodes.

The polarizable electrode produced in this way has a high electrostatic capacity, and can be preferably used by being incorporated as a capacitor of cylinder type, laminated type, coin type or the like. Hereinafter, the present invention will be described in detail with reference to examples. The present invention is not limited to these examples.

8 ~ in a constant-temperature dryer adjusted to 120 ° C; after 10 hours vacuum drying, the activated carbon lg was allowed to cool in a desiccator containing silica gel as the desiccant. Weighed out. To each Erlenmeyer flask, add 50 ml of N / 10 sodium hydrogen carbonate aqueous solution, N / 10 sodium carbonate aqueous solution, N / 10 sodium hydroxide aqueous solution, N / 10 sodium ethoxide ethanol solution, and 160 rpm at 25 ° C. Shake for hours. After shaking, the supernatant and precipitate were separated by centrifugation, 20 ml of the supernatant was accurately weighed into a 100 ml triangular flask, and titrated with N / 10 hydrochloric acid using methyl red as an indicator. Similarly, a blank test was performed with no sample! / And the solution, and the base consumption was calculated by the following formula.

[0036] (Base consumption) = ((Blank test titration) (Titration)) X 0. l X f X 50 / 20f = Fatter hydrochloride

[0037] Base consumption of each of NaHCO 3, Na 2 CO 3, NaOH, and Na (OCH 2 CH 3) A, B,

3 2 3 2 3

Assuming C and D, the surface functional group is represented by the formula;

Carboxyl group

(Formula 1)

Rataton group = B— A (meq / g) (Formula 2)

Hydroxyl = C B (meq / g) (Formula 3)

Quinone group = D— C (meq / g) (Formula 4)

<Measurement method of alkali metal content> Weigh the alumina crucible after baking at 900 ° C and allowing it to cool in a desiccator containing silica gel. 8 ~ in a thermostatic oven adjusted to 120 ° C; after vacuum drying for 10 hours, 20g of activated carbon cooled in a desiccator containing silica gel as a desiccant is placed in a 50ml alumina crucible, and the weight of crucible + activated carbon is 0 Weighed accurately to lmg. The alumina crucible containing the sample was placed in an electric furnace, and with the dry air introduced at 20 L / min into the electric furnace, the temperature was raised to 200 ° C in 1 hour, and further increased to 700 ° C over 2 hours. The temperature was raised and maintained at 700 ° C for 14 hours to incinerate. After completion of ashing, the mixture was allowed to cool in a desiccator containing silica gel, and the weight of the crucible + ash was accurately measured to 0.1 mg, and the ash content was calculated from Equation 5.

[0039] Ash content (ppm) = {(crucible + ash weight) (crucible weight) / (crucible + activated carbon weight) (crucible weight)} X 10000000 (Formula 5)

[0040] Add 10 ml of 35% hydrochloric acid and 30 ml of ultrapure water to an alumina crucible containing ash, heat and concentrate on an electric outlet, take the cooled solution in a 50 ml volumetric flask, and align with the mark with ultrapure water. This was used as the measurement solution. The prepared measurement solution was analyzed with an ICP emission analyzer Optima4300DV manufactured by Perkin Elma Co., Ltd. From the obtained value, the amount of metal in the activated carbon was calculated from Equation 6.

[0041] Metal content (ppm) = {Metal concentration (ppm) by ICP issue analysis / Ashed activated carbon weight

(g)} X 50 (Formula 6)

[0042] <Method for measuring chloride ion concentration>

8 ~ in a constant-temperature dryer adjusted to 120 ° C; after 10 hours vacuum drying, 10g of activated charcoal cooled in a desiccator containing silica gel as a desiccant is accurately weighed up to 0.1mg in a 200ml stoppered Erlenmeyer flask 100 ml of distilled water was added, a condenser was attached, and the mixture was refluxed for 30 minutes. After refluxing, the solution was separated into activated carbon and filtrate by filtration before the solution cooled. After separation, the filtrate was cooled, and the peak area of chloride ions was determined by ion chromatography. The chloride ion concentration contained in the filtrate was determined from a calibration curve prepared using an aqueous sodium chloride solution dried at 600 ° C, and the chloride ion concentration in the activated carbon was calculated using Equation 7.

[0043] Chloride ion concentration in activated carbon (ppm) = (Cl-Ion concentration in filtrate (ppm)

/ Activated carbon weight (g)) X 100 (Formula 7)

Nitrogen adsorption isothermal at 77K of activated carbon using BELSORP-mini made by Nippon Bell The line was measured. Using the BET equation to analyze the obtained adsorption isotherm, calculate the specific surface area from the straight line in the region of the relative pressure p / p = 0.001 -0.1 of the obtained curve.

0

did.

[0045] Example 1

Steam is supplied to kerosene combustion gas (mixed gas of H ○, CO, CO, N) and water vapor partial pressure is 3

2 2 2

In activated gas adjusted to 5%, coconut husk activated carbon (specific surface area 1 800 m ² / g) steam-activated at 900 ° C. was washed in 0.1N hydrochloric acid and then desalted with ion-exchanged water. After desalting, it was dried at 120 ° C and deoxidized at 700 ° C under kerosene combustion gas atmosphere for 30 minutes. After the deoxidation treatment, heat treatment was performed at 900 ° C. in a nitrogen atmosphere for 120 minutes. Table 1 shows the processing conditions. The obtained heat-treated activated charcoal was pulverized with a ball mill to obtain activated carbon powder for a non-aqueous polarizable electrode having a center particle diameter of 7 m. Table 2 shows the results of measuring the surface functional groups, alkali and alkaline earth metal contents, chloride ion concentration, and BET specific surface area of the obtained activated carbon.

[0046] The activated carbon powder, Denka Black (conductive material) and polytetrafluoroethylene (binding material) manufactured by Denki Kagaku Kogyo Co., Ltd. were kneaded so as to have a weight ratio of 80:10:10. An activated carbon electrode sheet having an electrode forming density of 0.60 g / cm ³ and a thickness of 400 m was produced by rolling the sheet. Cut this activated carbon electrode sheet as shown in Fig. 1 and crimp it onto aluminum expanded metal (manufactured by Nikkin Kako Co., Ltd.) as shown in Fig. 2 and use an ultrasonic welder to make aluminum lead wires (manufactured by Hosen Co., Ltd.). Was welded to aluminum expanded metal. After welding, it was vacuum dried at 150 ° C to produce a sheet electrode.

[0047] Cellulosic separator in glove box (Japan Advanced Paper Industries TF

40), this sheet-like electrode is stacked and inserted into a bag-like aluminum laminate 50mm XI 50mm (manufactured by Hosen Co., Ltd.) as shown in Fig. 3, and 1 · Omol / L triethyl inside. A propylene carbonate solution of methylammonium tetrafluoroborate was injected, and after impregnation, the opening was heat sealed to produce an electric double layer aluminum laminate capacitor as shown in Fig. 4.

[0048] The electric double layer capacitor produced as described above was charged at a constant current with an electric double layer capacitor charge / discharge tester manufactured by Power System Co., Ltd. at room temperature, up to an ultimate voltage of 2.7V, and ImA / cm ² per electrode surface area. 2. After supplementary charging is completed under a constant voltage of 7V2 hours Discharge at ImA / cm ² . This discharge cycle was repeated 5 times. The data for the fifth cycle was calculated by the energy conversion method and used as the capacitance.

[0049] After the initial capacitance measurement, the gas generation amount was measured by holding for 240 hours while applying a voltage of 2.5V in a constant temperature bath at 60 ° C. The amount of gas generated was calculated from buoyancy. Table 3 shows the capacitance and the amount of gas generated per activated carbon.

[0050] Example 2

Activated carbon for non-aqueous polarizable electrodes was obtained in the same manner as in Example 1 except that the coconut shell activated carbon used in Example 1 was heat-treated at 1100 ° C. in a nitrogen atmosphere for 120 minutes. Table 1 shows the treatment conditions and Table 2 shows the physical properties of the obtained activated carbon. Further, in the same manner as in Example 1, an electric double layer methanol laminate capacitor was produced, and the capacitance and gas generation amount were measured. The results are shown in Table 3.

[0051] Example 3

Activated carbon for non-aqueous polarizable electrodes was obtained in the same manner as in Example 1 except that the coconut husk activated carbon used in Example 1 was heat-treated at 1200 ° C. in a nitrogen atmosphere for 120 minutes. Table 1 shows the treatment conditions and Table 2 shows the physical properties of the obtained activated carbon. Further, in the same manner as in Example 1, an electric double layer methanol laminate capacitor was produced, and the capacitance and gas generation amount were measured. The results are shown in Table 3.

[0052] Example 4

The coconut husk activated carbon used in Example 1 was washed with 0.1N hydrochloric acid and then desalted with ion-exchanged water. After desalting, it was dried at 120 ° C, deoxidized at 500 ° C for 15 minutes in an atmosphere adjusted to 30% water vapor partial pressure by adding steam to kerosene combustion gas. After deoxidation treatment, heat treatment was performed at 900 ° C in a nitrogen atmosphere for 30 minutes. Except for these treatments, activated carbon for non-aqueous polar electrodes was obtained in the same manner as in Example 1. Table 1 shows the treatment conditions, and Table 2 shows the physical properties of the obtained activated carbon. Further, an electric double layer aluminum laminated capacitor was produced in the same manner as in Example 1, and the capacitance and gas generation amount were measured. The results are shown in Table 3.

[0053] Example 5

The non-oxidized coconut shell activated carbon used in Example 1 was deoxidized at 850 ° C in a kerosene combustion gas atmosphere for 60 minutes, and heat treated at 900 ° C in a nitrogen atmosphere for 60 minutes. An activated carbon for an aqueous polarizable electrode was obtained. Table 1 shows the various treatment conditions, and Table 2 shows the physical properties of the obtained activated carbon. Furthermore, an electric double layer aluminum laminated capacitor was produced in the same manner as in Example 1, and the capacitance and gas generation amount were measured. The results are shown in Table 3.

[0054] Example 6

2 2 2

An activated carbon for non-aqueous polarizable electrodes was obtained in the same manner as in Example 1 except that coconut husk activated carbon (specific surface area 1 550 m ² / g) steam-activated at 900 ° C in activated gas adjusted to 5% was used. It was. Table 1 shows the treatment conditions, and Table 2 shows the physical properties of the obtained activated carbon. Further, an electric double layer aluminum laminated capacitor was produced in the same manner as in Example 1, and the capacitance and gas generation amount were measured. The results are shown in Table 3.

[0055] Example 7

2 2 2

In the activated gas adjusted to 5%, activated carbon for non-aqueous polarizable electrodes was obtained in the same manner as in Example 1 except that coconut husk activated carbon (specific surface area 1 740 m ² / g) steam-activated at 900 ° C was used. It was. Table 1 shows the various treatment conditions, and Table 2 shows the physical properties of the obtained activated carbon. Further, an electric double layer aluminum laminated capacitor was produced in the same manner as in Example 1, and the capacitance and gas generation amount were measured. The results are shown in Table 3.

[0056] Example 8

2 2 2

Non-aqueous system as in Example 1 except that coconut husk activated carbon (specific surface area 1 960m ² / g) steam-activated at 900 ° C was used in the activated gas adjusted to 5%, and no heat treatment was applied. Activated carbon for polarizable electrodes was obtained. Table 1 shows the various treatment conditions, and Table 2 shows the physical properties of the obtained activated carbon. Further, an electric double layer aluminum laminated capacitor was produced in the same manner as in Example 1, and the capacitance and gas generation amount were measured. The results are shown in Table 3.

[0057] Comparative Example 1

The coconut husk activated carbon used in Example 1 was washed with 0.1N hydrochloric acid and then desalted with ion-exchanged water. After desalting, it was dried only at 120 ° C and pulverized with a ball mill to obtain activated carbon powder for non-aqueous polarizable electrodes having a center particle size of 6 m. Table 2 shows the physical properties of the obtained activated carbon. Further In the same manner as in Example 1, an electric double layer aluminum laminated capacitor was produced, and the capacitance and gas generation amount were measured. The results are shown in Table 3.

[0058] Comparative Example 2

Activated carbon for non-aqueous polarizable electrodes was obtained in the same manner as in Example 1, except that the coconut shell activated carbon used in Example 1 was not deoxidized in a combustion gas atmosphere. Table 1 shows the treatment conditions, and Table 2 shows the physical properties of the obtained activated carbon. Furthermore, an electric double layer aluminum laminate capacitor was produced in the same manner as in Example 1, and the capacitance and gas generation amount were measured. The results are not shown in Table << 3.

[0059] Comparative Example 3

Activated carbon for non-aqueous polarizable electrodes was obtained in the same manner as in Example 1 except that the coconut shell activated carbon used in Example 1 was heat-treated at 1300 ° C. in a nitrogen atmosphere for 120 minutes. Table 1 shows the treatment conditions and Table 2 shows the physical properties of the obtained activated carbon. Further, in the same manner as in Example 1, an electric double layer methanol laminate capacitor was produced, and the capacitance and gas generation amount were measured. The results are shown in Table 3.

[0060] Comparative Example 4

Non-aqueous system as in Example 1 except that the coconut husk activated carbon used in Example 1 was deoxidized at 800 ° C for 30 minutes in a combustion gas atmosphere and heat treated at 600 ° C for 120 minutes in a nitrogen atmosphere. Activated carbon for polarizable electrodes was obtained. Table 1 shows the treatment conditions, and Table 2 shows the physical properties of the obtained activated carbon. Further, an electric double layer aluminum laminated capacitor was produced in the same manner as in Example 1, and the capacitance and gas generation amount were measured. The results are shown in Table 3.

[0061] Comparative Example 5

Anisotropic raw coatas (H / C = 0.4) obtained by heat-treating coal-based heavy oil as raw materials were pulverized with a ball mill to a center particle size of 10 m, and then activated with alkali. The obtained alkali-activated activated carbon was washed in 90 ° C, 0.5N hydrochloric acid and then desalted with ion-exchanged water. After desalting, it was dried at 120 ° C. for 24 hours to obtain activated carbon powder for non-aqueous polarizable electrodes. Table 2 shows the physical properties of the obtained activated carbon. Further, an electric double layer aluminum laminated capacitor was produced in the same manner as in Example 1, and the capacitance and gas generation amount were measured. The results are shown in Table 3.

[0062] Comparative Example 6 The alkaline activated carbon of coal-based raw coatas prepared in Comparative Example 5 was washed in 90 ° C, 0.5N hydrochloric acid, and then desalted with ion-exchanged water. After desalting, it was dried at 120 ° C. for 24 hours, transferred to an aluminum vat, and subjected to deoxidation treatment and heat treatment in the same manner as in Example 1. Table 2 shows the physical properties of the obtained activated carbon. Further, an electric double layer aluminum laminated capacitor was produced in the same manner as in Example 1, and the capacitance and gas generation amount were measured. The results are shown in Table 3.

[table 1]

Capacitance Gas generation amount

F / g F / cc (m L Z g—activated carbon)

Example 1 29.8 18.0 1.3

Example 2 26.3 17,8 1.1

Example 3 23.1 15,7 0.8

Example 4 28.9 17.7 2.0

Example 5 28.1 17.3 1.5

Example 6 28.7 19.0 1.5

Example 7 29.6 18.1 1.2

Example 8 31Λ 15.2 1.0

Comparative Example 1 29.7 18,0 3,2

Comparative Example 2 29.2 17.5 2,6

Comparative Example 3 19.4 14.0 0.6

Comparative Example 4 28.6 17.2 2.9

Comparative Example 5 43.6 26.4 5.4

Comparison ^ 6 32.0 20.2 2.5

[0066] As is apparent from Table 3, it can be seen that the capacitor using the non-aqueous polarizable electrode made of the activated carbon of the present invention generates less gas than the capacitor using other activated carbon. . In addition, deoxidation in an oxidizing gas atmosphere and heat treatment in an inert gas atmosphere at 1300 ° C can suppress gas generation, but the specific surface area decreases by 20% or more, and the capacitance is also significantly increased. It turns out that it falls.

Industrial applicability

[0067] The activated carbon of the present invention is one in which the concentration of chlorine ions remaining by acid cleaning is efficiently reduced, and the crystallinity is increased while the surface functional groups are reduced, improving the conductivity. You can make it S. Therefore, when the activated carbon of the present invention is produced on a polarizable electrode and used for a non-aqueous electric double layer capacitor, it is difficult to cause a short circuit due to reduction deposition of a metal having a high capacitance. It exhibits a high self-discharge retention rate, is excellent in durability, and generates particularly little gas. Therefore, it is suitable for a capacitor having a large capacity and a high output. Brief Description of Drawings

[0068] Fig. 1 is an activated carbon electrode sheet used in the present invention.

FIG. 2 is a schematic view showing a state where an activated carbon electrode sheet is pressure-bonded to an expanded metal.

FIG. 3 is a schematic view of an aluminum laminate processed into a bag shape.

FIG. 4 is a schematic view of an electric double layer aluminum laminated capacitor. Explanation of symbols

1 Lead wire with tab

2 Aluminum expanded metal 3 Heat paper

Claims

The scope of the claims

[1] A coconut husk activated carbon obtained by carbonizing coconut shells and activating water vapor, wherein the total surface functional groups are 0.4 meq / g or less, the surface functional groups do not contain a carboxyl group and a rataton group, and quinones The group is 50% or more of the total surface functional groups, the alkali metal content is 50 to 500 ppm, the chlorine ion concentration is 0.1 ppm to 20 ppm, and the BET specific surface area is 1500 to 2000 m ² / g. Activated carbon characterized by that.

[2] Steam activated coconut shell activated carbon is washed with hydrochloric acid, then deoxidized in an oxidizing gas atmosphere at 500 to 1000 ° C, and then further heat treated at 900 to 1200 ° C in an inert gas atmosphere A method for producing activated carbon, comprising:

[3] The method for producing activated carbon according to claim 2, wherein the oxidizing gas is a combustion gas or a gas obtained by adding steam to the combustion gas.

[4] A non-aqueous polarizable electrode comprising the activated carbon according to claim 1.

5. An electric double layer capacitor using the polarizable electrode according to claim 3.