KR100453922B1 - Spherical active carbon and methods for preparing the same, and electric double layer capacitor using the same - Google Patents

Abstract

The present invention relates to a spherical activated carbon, and a method for manufacturing the same, and an electric double layer capacitor using the same, more specifically, spherical activated carbon and a method for manufacturing the same, including spherical spherical particles satisfying the following formula (1): It provides an electric double layer capacitor using the same.

[Equation 1]

0.99 ≤ a / b ≤ 1

(Wherein a is the short diameter of the particle and b is the long diameter of the particle)

Description

SPHERICAL ACTIVE CARBON AND METHODS FOR PREPARING THE SAME, AND ELECTRIC DOUBLE LAYER CAPACITOR USING THE SAME}

The present invention relates to spherical activated carbon and a method for manufacturing the same, and an electric double layer capacitor using the same, and more particularly, to spherical activated carbon having a particle size of several to several tens of micrometers and a specific surface area of 500 m 2 / g or more.

[Prior art]

Electric double-layer capacitors (Electric Double-layer Capacitors) is an electric double-layer (Electric Double-layer) formed at the interface between the electrode and the electrolyte (Electric Double-layer) is a device for storing charge by charging ions on the electrolyte and electrons on the electrode. Carbon materials are commonly used as electrode materials for such electric double layer capacitors. In order for the carbon materials to exhibit excellent electric double layer capacitor characteristics, 1) electrodes must have a large specific surface area including many pores, and 2) electrodes have excellent conductivity. When fabricated, the electrode resistance should be small. 3) The particle shape should be spherical and the size distribution is uniform, so that the capacitor can be filled with a large amount. Large charge levels result in a large charge storage capacity per volume of the capacitor.

Activated carbon (also known as porous carbon) has a high porosity and a large specific surface area, so it is widely used in various fields such as water treatment column packing materials, molecular sieve carbon (MSC), etc. in addition to electric double layer capacitors. It is used.

The production method of the activated carbon is known as physical activation by vaporization of charcoal in the presence of oxidizing gas, or chemical activation by carbonization of carbonaceous impregnated into a chemical agent. Chemical method of impregnating phenol-formaldehyde resin with potassium hydroxide (KOH) as a method for producing activated carbon and carbonizing it under nitrogen atmosphere at a temperature of 500 to 900 ° C. and carbonizing the resin at 900 ° C. and carbonizing it in a carbon dioxide atmosphere. A method for producing activated carbon having a surface area of 2000 m 2 / g or more and a pore volume of 1.0 cm 3 / g or more by using a physical method in which the degree of burn-off vaporizes has been reported [Carbon 38 (2000), 817-). 824]. In the case of the above method, the physical activation method shows a denser surface than the chemical activation method, but there is still a problem in that the non-spherical shape is irregular.

In addition, the production method of the spherical activated carbon is representative of activated MCSO (activated mesocarbon microbeads) of Osaka gas, the method is activated by using MCMB potassium hydroxide (KOH) of about 3000 m 2 / g high Although activated carbon having a specific surface area is manufactured, there is a disadvantage that the manufacturing cost of MCMB is expensive.

Further, according to Japanese Patent Laid-Open No. 6-144817, in the method for producing activated carbon from a carbon raw material and an activating aid, the ratio of the carbon raw material and the activating aid is supplied in a weight ratio of 1: 2 to 1: 8, and is inert gas atmosphere. A method of continuously producing activated carbon having a high specific surface area by performing continuous treatment at a temperature of 450 to 550 ° C. or lower and then continuously activating at a temperature of 600 to 1000 ° C. or lower in an inert gas atmosphere. Doing. In addition, Japanese Patent Application Laid-Open No. 2000-128518 discloses a method for producing activated carbon or activated carbon fibers by activating a carbon material using an alkali metal compound as an activator, wherein an inert containing 10-40 vol% carbon dioxide after completion of the activation reaction. A method of treating the activated carbon or activated carbon fibers below an activation reaction temperature (below 440 ° C.) under a gas atmosphere, and an electric double buffer capacitor using the same as an electrode are described. The above methods are used to produce activated carbon using an activator, but there is also a problem that the prepared activated carbon is not spherical.

Therefore, if the spherical and large specific surface area of activated carbon is simply manufactured, a large amount can be filled when used as an electrode material of the electric double layer capacitor, thereby improving the charge storage capacity of the capacitor.

In view of the problems in the prior art, an object of the present invention is to provide spherical activated carbon having a particle size of several to several μm, a specific surface area of 500 m 2 / g or more, and a high capacitance value per unit mass.

Another object of the present invention is to provide a method for producing spherical activated carbon having a large specific surface area by a simple method.

Another object of the present invention is to provide an electric double layer capacitor having a high capacitance value by including the spherical activated carbon as an electrode active material.

1 is a scanning electron micrograph at 1000 magnification of spherical activated carbon prepared in Example 1 of the present invention.

FIG. 2 is a graph showing the results of cyclic voltammetry performed in Example 4 of the present invention. FIG.

In order to achieve the above object, the present invention

In spherical activated carbon,

It provides a spherical activated carbon containing 10% by weight or more of spherical spherical particles satisfying the following formula (1).

[Equation 1]

0.99 ≤ a / b ≤ 1

Wherein a is the short diameter of the particle and b is the long diameter of the particle.

In addition, the present invention provides a method for producing spherical activated carbon,

a) iii) a carbon precursor; And

Ii) hydrophobic minerals

Mixing and carbonizing the mixture by heat treatment under an inert gas atmosphere; And

b) impregnating the carbide of step a) in the activator and then in an inert gas atmosphere.

Heat treatment to activate carbide

It provides a manufacturing method comprising a.

The present invention also provides an electric double layer capacitor comprising the spherical activated carbon of the substrate as an electrode active material.

Hereinafter, the present invention will be described in detail.

The present invention provides a spherical activated carbon having a large specific surface area and a high capacitance value per unit mass, a manufacturing method thereof, and an electric double layer capacitor using the same. According to this method, spherical carbon is prepared by adding silica to carbon precursors such as resin and pitch instead of activated MCMB, which is expensive in the prior art, and spherical carbon is activated using an activator to make spherical carbon more easily than conventional methods. Activated carbon can be obtained. In addition, the electric double layer capacitor using the spherical activated carbon as an electrode active material exhibits a high capacitance value and is suitable for application to various other fields such as for backing up various power sources.

Such spherical activated carbon of the present invention preferably contains 10% by weight or more of spherical spherical particles satisfying the following formula (1).

In addition, the remaining particles of the spherical activated carbon of the present invention preferably comprises spherical spherical particles satisfying the following formula (2).

[Equation 1]

0.99 ≤ a / b ≤ 1

[Equation 2]

0.1 ≤ a / b ≤ 0.99

Wherein a is the short diameter of the particle and b is the long diameter of the particle

It is preferable that the spherical activated carbon of the present invention satisfying the above conditions has an average particle diameter of 1 to 40 µm.

In addition, the specific surface area of the spherical activated carbon of the present invention has a large value of 500 m 2 / g or more. The specific surface area can be measured by a conventional method such as BET method.

The capacitance value per unit mass of the spherical activated carbon of the present invention exhibits a high value of 50 F / g or more, and can be used as an electrode active material such as an electric double layer capacitor.

In addition, the present invention can produce spherical activated carbon having a large specific surface area and high capacitance value by a simple method. This will be described in more detail as follows.

First, the present invention performs a step of carbonizing by a) mixing a carbon precursor and a hydrophobic inorganic material and heat treatment in an inert gas atmosphere.

Since the carbon precursor used in the present invention may be in a solid powder state that can be mixed with an inorganic substance, there is no particular limitation on the type of precursor, and preferably, resin, pitch, or a mixture thereof is used.

In the present invention, the resin used as the carbon precursor is preferably a thermosetting synthetic resin, and the thermosetting synthetic resin is a phenolics resin, furan resin, epoxy resin, polyacrylonitrile resin, 1 from the group consisting of polyimide resin, polybenzimidazole resin, polyphenylene resin, biphenol resin, divinylbenzene styrene copolymer, and cellulose One or more selected may be used.

In addition, the pitch using the carbon precursor in the present invention may be used such as petroleum pitch or coal pitch.

In addition, the present invention makes it possible to obtain carbon having a spherical shape by adding an inorganic material whose surface is hydrophobically treated to the carbon precursor. When the carbon precursor is carbonized without introducing inorganic fine particles as in the prior art, lumped carbon is obtained. However, as in the present invention, when carbonized by mixing hydrophobic inorganic materials treated with hydrophobic surfaces of the inorganic fine particles, spherical carbon is obtained, and thus no grinding process is required. The hydrophobic inorganic material used in the present invention surrounds the surface of the carbon precursor powder to prevent agglomeration of carbon particles in the carbonization process, and also provides a high surface tension when the particles shrink in the carbonization process so that the particles become spherical. Induce. Therefore, when carbonized by introducing inorganic material whose surface is not hydrophobicly treated, lumped carbon is produced, so hydrophobicity of the inorganic surface becomes a very important factor for producing spherical carbon.

Such hydrophobic inorganic materials may be used such as silica, zeolite, alumina, titania (TiO ₂ ), ceria (CeO ₂ ), etc., on which the surface is hydrophobically treated. In addition, other types of inorganic materials may be used as long as they are suitable for the configuration of the present invention in addition to those exemplified above. Among them, it is more preferable to use silica which can be easily dissolved and removed by an acidic or alkaline solution and which is inexpensive and has a small particle size. Specific examples of the hydrophobic surface-treated silica include Cabosil (Cab-O-SIL TS-720, TS-610, TS-530, TS-500, TG-308F, TG-810G530, etc.). ) And Deggusa's aerosils (AEROSIL R972, R974, R812, R812S, R202). These inorganic substances may use a commercialized product, and may also use it synthetically.

As a method of synthesizing the hydrophobic inorganic material, for example, a general inorganic material having a non-hydrophobic surface and an organosilane surface treatment agent such as trimethylchlorosilane are added to a solvent such as toluene, and then refluxed while stirring to make the surface hydrophobic. You can easily get minerals.

The mixing ratio of the carbon precursor and the inorganic material whose surface is hydrophobically treated is preferably mixed in a weight ratio of 100: 0.1 to 1000. The mixing is preferably carried out in a mortar, but is not limited thereto. At this time, it is difficult to produce spherical silicon carbide when the amount of the hydrophobic inorganic substance added is less than 0.1 part by weight with respect to 100 parts by weight of the carbon precursor, and when the amount exceeds 1000 parts by weight, it is difficult to obtain the effect as much as the amount added.

In the present invention, when the mixture of the carbon precursor and the inorganic material whose surface is hydrophobically treated is carbonized by heat treatment under an inert gas (for example, argon, nitrogen, helium, etc.) atmosphere, a carbide having a spherical shape is obtained. The heat treatment conditions are preferably carried out at a temperature increase rate of 0.1 to 100 ℃ / min carried out at 200 to 1500 ℃ for 1 minute to 50 hours.

In addition, the present invention provides a method for producing spherical activated carbon, b) impregnating the carbide of the above step in the activator (activator) and heat treatment in an inert gas atmosphere to perform the step of activating the carbide.

In this invention, a specific surface area is enlarged by making a spherical carbon pore using the said activator. The activator uses a solution of an alkali metal salt, preferably a potassium hydroxide (KOH) solution.

The impregnation conditions are preferably carried out for 1 minute to 50 hours in an alkali metal solution of 0.5 to 10 normal concentration.

The heat treatment is preferably carried out at a heating rate of 0.1 to 100 ℃ / min at 500 to 900 ℃ for 1 minute to 50 hours.

In addition, the present invention is to prepare the spherical activated carbon by washing the activated carbide by adding an acid solution. The acid solution used for the washing is preferably hydrochloric acid (HCl).

In addition, the present invention can use spherical activated carbon having a large specific surface area and high capacitance as an electrode active material of an electric double layer capacitor.

For example, the electric double layer capacitor may be manufactured by including an electrode including the spherical activated carbon and a current collector, a separator inserted between the electrodes, and an electrolyte solution impregnated therein.

The electrode is prepared by adding a spherical activated carbon and a binder in a weight ratio of 10: 0.5 to 2 and stirring the paste to prepare a paste, and then applying it to a current collector metal material, compressing it, and drying it to form a laminate.

The binder may be polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), cellulose, or the like. The dispersant may be isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, or the like, and the metal material for the current collector may be made of stainless steel, titanium, or aluminum mesh or foil. Etc.

The separator is a component that blocks internal short circuits of two electrodes and impregnates the electrolyte, and includes a polymer, glass fiber mat, kraft paper, Celgard 2400, 2300 (manufactured by Hoechest Celanese Corp.) separator, poly A propylene separator (manufactured by Ube Industries Ltd. or Pall RAI).

In addition, the present invention, in order to further reduce the resistance of the electrode, acetylene black series (Chevron Chemical Company or Gulf Oil Company, etc.), Ketjenblack EC series (Armak Company) Carbon black (Armak Company), Vulcan XC-72 (Cabot Company), Super P (MMM), etc. Prepared by the addition of further 5 to 20% by weight.

The electrolyte solution is used by dissolving an ionic salt at a concentration of 0.5 to 3 moles in an aprotic organic solvent having a high dielectric constant or a low viscosity, or an aqueous sulfuric acid solution having a weight ratio of 5% to 100% or 0.5 to 20 M potassium hydroxide. An aqueous solution of is used.

As described above, in the present invention, when a spherical activated carbon having a large specific surface area is manufactured by a simple method and used as an electrode active material of an electric double layer capacitor, a large amount of filling is possible, and thus an electric double layer capacitor having a large charge storage capacity can be manufactured.

Hereinafter, the present invention will be described in detail with reference to the following examples, which are not intended to limit the content of the present invention.

EXAMPLE

Preparation of Spherical Carbon

[Production Example 1]

CAB-O-SIL TS-530 fumed silica, surface-treated with hexamethyldisilazane in phenolic resin, a precursor, Thereafter, the mixture was heated under an argon gas atmosphere at a temperature rising rate of 10 ° C./min, and heat treated at 700 ° C. for 1 hour to obtain spherical carbon.

Preparation of Spherical Activated Carbon

Example 1

The spherical carbon obtained in Preparation Example 1 was impregnated with KOH solution of 2 normal concentration at 85 ° C. for 3 hours, dried, heated at an elevated temperature rate of 10 ° C./min under an argon gas atmosphere, and heat-treated at 700 ° C. for 2 hours. Activated carbon was obtained. Then, the mixture was washed with 0.5 normal HCl solution at 85 ° C. for 3 hours and then dried in a 120 ° C. vacuum oven for 24 hours. The spherical activated carbon thus prepared had a specific surface area of 2900 m 2 / g, and a scanning electron micrograph of 1000 magnification was shown in FIG. 1. The ratio (a / b) of the short diameter a and the long diameter b of the spherical activated carbon particles was 0.99, and the average particle diameter was 12 µm.

Example 2

Spherical activated carbon was prepared in the same manner as in Example 1, except that the mixture was heat treated at 800 ° C. for 2 hours. The ratio (a / b) of the short diameter a and the long diameter b of the spherical activated carbon particles was 0.99, and the average particle diameter was 11 mu m.

Example 3

Spherical activated carbon was prepared in the same manner as in Example 1, except that naphthalene isotropic pitch was used as the precursor. The ratio (a / b) of the short diameter a and the long diameter b of the spherical activated carbon particles was 0.99, and the average particle diameter was 18 µm.

Electric double layer capacitor using spherical activated carbon as electrode active material

Example 4

The spherical activated carbon prepared by the method of Example 1 was subjected to a capacitor performance test in 2M sulfuric acid solution.

First, spherical activated carbon, a Ketjenblack conductive material and a Teflon binder were dispersed in isopropyl alcohol in a ratio of 10: 1: 1 in order to prepare an electrode. It was applied to a 1 cm 2 stainless steel exmet current collector (sus Exmet) and then compressed and dried at 120 ℃ for 24 hours. After vacuum-impregnating sulfuric acid electrolyte in the prepared electrode and stabilizing, a cyclic scanning potential experiment was performed by using a platinum counter electrode and a saturated calomel reference electrode. The potential scanning speed was 1 mW / s. The capacitance per unit mass was calculated by dividing the current value appearing at the cyclic scanning potential by the scanning speed and the mass of the electrode active material. And the capacitance value per unit mass is shown in FIG. 2, it can be seen that the spherical activated carbon of the present invention exhibits a high capacitance value per unit mass of 200 F / g or more when used as an electrode material of an electric double layer capacitor.

As described above, the spherical activated carbon manufacturing method of the present invention has a specific surface area of 500 m 2 / g or more, it is possible to manufacture spherical activated carbon more simply than the conventional process, and when the spherical activated carbon prepared in this way is applied to an electric double layer capacitor The capacitance value can be obtained.

Claims (15)

delete delete delete delete In the manufacturing method of spherical activated carbon, a) iii) a carbon precursor; And Ii) hydrophobic minerals Mixing and carbonizing the mixture by heat treatment under an inert gas atmosphere; And b) impregnating the carbide of step a) in the activator and then in an inert gas atmosphere. Heat treatment to activate carbide Manufacturing method comprising a. The method of claim 5, wherein The carbon precursor of step iii) is a resin, a pitch or a mixture thereof. The method of claim 6, The resin is a phenol resin, furan resin, epoxy resin, polyacrylonitrile resin, polyimide resin, polybenzimidazole resin, polyphenylene ( A polyphenylene resin, a thermosetting synthetic resin containing biphenol resins, a divinylbenzene styrene copolymer, and a manufacturing method selected from the group consisting of cellulose. The method of claim 6, The pitch is coal pitch or petroleum pitch. The method of claim 5, wherein The hydrophobic inorganic material of a) step ii) is selected from the group consisting of silica, zeolite, alumina, titania, and ceria whose surface is hydrophobically treated. The method of claim 5, wherein I) the carbon precursor of step a) and the hydrophobic inorganic material of ii) are mixed in a weight ratio of 100: 0.1 to 1000. The method of claim 5, wherein The activator of step b) is a manufacturing method of an alkali metal salt. The method of claim 5, wherein Impregnation of step b) is carried out for 1 minute to 50 hours in an alkali metal solution of 0.5 to 10 normal concentration. The method of claim 5, wherein The heat treatment of step a) is carried out for 1 minute to 50 hours at a heat treatment temperature of 200 to 1500 ℃. The method of claim 5, wherein The heat treatment of step b) is carried out for 1 minute to 50 hours at a heat treatment temperature of 500 to 900 ℃. delete