KR20020040645A - Method of preparing fibrous carbonaceous nano-materials and electrode materials for electrochemical capacitor using them - Google Patents

Abstract

PURPOSE: A manufacturing method of fibrous carbonaceous nano material and electrode material for electro chemical capacitor using the same are provided to accomplish charge storage and emission performance, reduce manufacture cost, obtain desirable crystalline, and accomplish fast electrolytic double layer formation and removal characteristic. CONSTITUTION: For manufacturing fibrous carbonaceous nano material, nickel particle is obtained by precipitating and γ-ferrite is obtained by colloidal dispersion and freeze drying. The nickel particle 10 mg and the γ-ferrite of average particle diameter 40 nm 60 mg are placed in a horizontal furnace having a quartz tube of an inner diameter 10 cm, and reduced in a reduction furnace at 550°C for 2 hours with hydrogen-helium mixed gas at a fluid speed of 4cm/sec. Then, carbon monoxide-hydrogen mixed gas having 80% carbon monoxide is reacted at a fluid speed of 200 ml/min at 580°C for 1.5 hours to manufacture fibrous ultra fine carbon. After reaction, the furnace is reduced with helium gas and cooled down to obtain fibrous carbonaceous nano material.

Description

Method of preparing fibrous carbon nanomaterials and electrode materials for electrochemical capacitors using them {Method of preparing fibrous carbonaceous nano-materials and electrode materials for electrochemical capacitor using them}

The present invention relates to an electrode material for electrochemical capacitors, in particular, to a method for producing a novel carbonaceous carbonaceous material (Fibrous carbonaceous nano materials) that can be used in the electrode material for an electric double layer capacitor, and an electrode material for an electrochemical capacitor using the same will be.

As the market for electric vehicles, decentralized and load leveling energy storage devices has expanded rapidly and newly created, the importance of electrode materials used in high performance capacitors is increasing day by day.

Electrochemical capacitors generally include electrolytic double layer capacitors (EDLC) utilizing physical charge storage of electrical double layers formed on surfaces of high specific surface area conductive materials, and similar capacitors such as hydrogen and cation adsorption and desorption from porous oxides. It is possible to distinguish between electrochemical oxide capacitors (EOC) using a watt, and hybrids thereof.

Among these, the electric double layer capacitor using formation / disassembly of the electric double layer on the surface is manufactured using granular and fibrous activated carbons, which are carbon materials having a high specific surface area, as electrode materials.

Since activated carbon is mainly manufactured through carbonization and activation using granular and fibrous resin-based and pitch-based raw materials, the production cost of activated carbon is low, and the final yield is about 10-50%. It acts as a factor to increase the unit price.

In the case of activated carbon fibers, a material with a specific surface area of 1200 m 2 / g has a storage capacity of 120 F / g when tested for material properties in aqueous sulfuric acid solution. Therefore, when the actual high performance capacitor is manufactured, it has a capacity of about 30 F / g, and the molecular carbon material (specific surface area: 1500 m 2 / g), which is a typical high specific surface carbon material, exhibits a storage capacity of 100 to 150 F / g. do.

Activated carbon and activated carbon fiber produced by activating a general carbon material is poor in high output characteristics because the electrical conductivity is relatively low.

In the case of mesoporous carbon ( Chem. Mater , 9 , 609) grown on the surface of zeolite or silica by gas phase, it can be expected to be an electrode material having high output characteristics due to high electrical conductivity, but due to manufacturing cost nearly 30 times that of activated carbon There was a problem that is not practical. In addition, there was also a problem that it is difficult to be processed because HF is used.

Therefore, an object of the present invention is to solve the problems of the prior art and the technical problems that have been requested from the past.

In other words, the present invention has a superior charge storage and emission capability than the conventional resin-based activated carbon and activated carbon fiber, and has a low manufacturing cost and excellent crystallinity, and thus is a novel fibrous carbon capable of exhibiting rapid electric double layer formation and removal characteristics. It is an object to provide a nanomaterial.

1 is a graph of the charge amount by the cyclic potential scanning method of the fibrous carbon nano material according to Example 2 of the present invention;

Figure 2 is a graph of the charge amount by the cyclic potential scanning method of the fibrous carbon nano material according to Example 3 of the present invention;

3 is a charge amount graph by a cyclic potential scanning method of the fibrous carbon nano material according to Example 4 of the present invention;

4 is a low magnification photograph of a high resolution transmission electron microscope of a fibrous carbon nanomaterial having an accordion type structure according to Example 1 of the present invention;

5 is a 9 million times higher magnification photograph of a high resolution transmission electron microscope of a fibrous carbon nanomaterial having an accordion type structure according to Example 1 of the present invention.

Method for producing a fibrous carbon nano material of the present invention for achieving this object,

Iron oxide (γ-ferrite) with an average particle diameter of 20 to 80 nm, prepared by colloidal dispersion, and nickel particles prepared by the precipitation method are kneaded at a ratio of iron oxide and nickel particles in a weight ratio of 6/4 to 9/1 (wt / wt). Then, it is reduced in a reducing atmosphere at 400 to 700 ° C., and then mixed with hydrogen at the surface of the catalyst in the mobile and / or fixed bed using carbon monoxide and / or hydrocarbon as the source gas, and gas phase decomposition at 500 to 700 ° C. on the surface of the catalyst to accordion It is characterized by producing a fibrous carbon nano material having a structure of the type.

Therefore, the method of the present invention uses a chemical vapor growth method of growing carbon filaments by using a kneaded metal of iron oxide and nickel particles prepared as described above as a basic catalyst and decomposing hydrocarbons such as ethylene on a catalyst. method).

As used herein, the term "base catalyst" refers to a kneaded metal before the reduction treatment, and "catalyst" refers to a kneaded metal after the reduction treatment. As used herein, the term "basic catalyst" means iron oxide before the reduction treatment, and "catalyst" means iron oxide after the reduction treatment.

The ultra-fine iron oxide particles are preferably so that the particles are easily kneaded with the nickel particles because the condensation between particles is extremely limited, so that water is dispersed in a colloidal phase with a solvent and kept frozen in a uniformly stable state. It is used by drying.

Precipitation method for the production of the nickel particles, R-J. Best, W. W. Russell,J. Am. Chem. Soc. , 76, According to 838), to obtain nickel bicarbonate precipitate by adding ammonium bicarbonate to an aqueous nickel nitrate solution, and drying and calcining to prepare nickel oxide, and finally calcined nickel oxide It is a method for producing ultra-fine nickel particles by reducing the.

The kneading ratio of the iron oxide and nickel particles thus prepared is preferably 6/4 to 9/1 (wt / wt). If it is 6/4 or less, the nickel particles are too large to obtain a fibrous one. There is a problem that soot (soot) is formed.

In order to reduce the catalyst in a reducing atmosphere, the reducing atmosphere may use a mixed gas of hydrogen and nitrogen, a mixed gas of hydrogen and argon, a mixed gas of hydrogen and helium, and the like. The content of hydrogen in the mixed gas is preferably 2 to 50% by volume. When the content of hydrogen is small, it is difficult to cause a reduction reaction, and when there is a large amount, there is a risk of explosion.

The temperature of the reduction treatment is usually 400 to 700 ° C., if the temperature is 400 ° C. or less, the reaction may not be easily initiated and a long time is required for the treatment. If the temperature is 700 ° C. or more, aggregation of fine particles may occur. The time of the reduction treatment can be varied by various conditions such as the reduction treatment temperature, which takes about 0.5 to 24 hours. As one specific example, a method of reducing the kneaded metal base catalyst by using a hydrogen-helium mixed gas at 550 ° C. for 2 hours may be mentioned.

In the source gas, hydrocarbons are unsaturated and / or saturated hydrocarbons composed of hydrogen and carbon, each having 1 to 4 carbon atoms such as acetylene (C ₂ H ₂ ), methane (CH ₄ ), ethylene (C ₂ H ₄ ), and ethane ( C ₂ H ₆ ), propylene (C ₃ H ₆ ), propane (C ₃ H ₈ ), butane (C ₄ H ₁₀ ), butylene (C ₄ H ₈ ), butadiene (C ₄ H ₆ ) and its isomers One or two or more selected from the group consisting of these may be used. Ethylene is particularly preferred in view of the price of raw gas, ease of handling, reactivity, and the like. Such hydrocarbons may be used in a single form or in a mixture with an inert gas such as Ar, He or the like.

The mixing ratio of the source gas and the hydrogen gas is preferably 5 to 92%, more preferably 10 to 90%. If the proportion of the source gas is 5% or less, the amount of carbon nanotubes produced is not economical, and if it is 92% or more, the reaction is terminated early, which is not economical either.

The temperature of the gas phase decomposition is preferably 500 to 700 ° C, more preferably 550 to 620 ° C. If the gas phase decomposition temperature is 500 ° C. or less, gas phase decomposition may not be completely performed or excessive time is required. If the temperature is 700 ° C. or more, the specific surface area is rapidly reduced by the disappearance of pores, thereby reducing the number of effective pores. The time of gas phase decomposition can be changed by various conditions such as the temperature of gas phase decomposition, and it takes about 10 minutes to 10 hours. As one specific example, the ethylene-hydrogen mixed gas may be reacted at a reaction temperature of 580 ° C. for 1.5 hours.

As described above, the nanotubes grown from the iron oxide particles and the nickel particles are replaced with helium gas and cooled to room temperature to finally recover the fibrous carbon nano material having the accordion structure. Carbon nanomaterials of this structure are novel and have not been reported before.

In some cases, the specific surface area may be increased by further performing an activation heat treatment on the manufactured fibrous carbon nanomaterial.

The activation heat treatment is performed for 10 minutes to 24 hours at 450 to 750 ° C. using a carbon dioxide-inert gas mixture having a mixing ratio of 1/9 to 9/1 (vol / vol), so that the overall volume is not significantly affected. Oxidative decomposition of some carbon nanomaterials. As a result, as described above, the specific surface area of the activated fibrous material is greatly increased. The activated fibrous carbon nano material may be used for electrode materials for high performance electrochemical capacitors. If the mixer is less than 1/9 takes a lot of time for the activation heat treatment, if more than 9/1 there is a problem that the reaction proceeds quickly and the structure is destroyed. In addition, if the activation heat treatment temperature is 450 ° C or less, the activation degree is low, if the 750 ° C or more there is a problem that the structure is destroyed. The activation heat treatment time has a range that can vary depending on the heat treatment temperature, and if the heat treatment for a short time at a relatively low temperature is almost no effect of heat treatment, if too much carbon component heat treatment for a long time at a relatively high temperature This oxidative decomposition causes a problem that the strength of the structure is lowered. Particularly preferred examples of the inert gas include argon (Ar) gas.

The present invention also relates to an electrode material for an electrochemical capacitor, in particular, an electrode material for an electric double layer capacitor, using the fibrous carbon nanomaterial prepared by the above method. Electrode materials for electrochemical capacitors are well known in the art and thus detailed description thereof will be omitted.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples thereof, but the scope of the present invention is not limited thereto.

Example 1

Nickel hydroxide was obtained by adding 2 g of ammonium bicarbonate to 500 ml of 0.5 M aqueous nickel nitrate solution, followed by drying in a vacuum oven at 100 ° C. for 24 hours and calcining at 500 ° C. for 2 hours to prepare nickel oxide. The calcined nickel oxide was reduced at 500 ° C. for 2 hours in a 1% H ₂ / He atmosphere to prepare nickel particles.

10 mg of the nickel particles prepared above, and fine particles of γ-ferrite (γ-Fe ₃ O ₄ ) particles having a mean particle size of 40 nm which were prepared by colloidal dispersion and freeze-dried (神 (和 彦, 表面, 32-3, 35) , 1994) 60 mg in a ceramic boat, placed in the center of a horizontal furnace equipped with a 10 cm inner diameter quartz tube, followed by a 4 cm / sec mixture of hydrogen and helium with a hydrogen mixing ratio of 20% per volume. The temperature was raised to 550 ° C. while flowing at a flow rate of and then reduced at 550 ° C. for 2 hours.

Then, the carbon monoxide-hydrogen mixed gas having a carbon monoxide mixing ratio of 80% was reacted at 580 ° C. for 1.5 hours at a flow rate of 200 ml / min to prepare fibrous microfine carbon, and after the reaction was completed, the atmosphere was replaced with helium gas. After cooling to room temperature, the fibrous carbon nano material was recovered from the ceramic boat. At this time, the weight of the recovered fibrous carbon nano material was 1220 mg.

The fibrous carbon nanomaterial was subjected to powder graphite crystallite analysis using a wide-angle X-ray diffractometer using a CuKα light source. The average interplanar distance (d ₀₀₂ ) of the fibrous carbon nanomaterials calculated from the diffraction pattern was investigated at a diffraction pattern of 5 to 90 ° under the conditions of ㎃ and 30 ㎸, which is 3.402 Å, indicating relatively high graphitization. 4 shows a photograph taken with a high resolution transmission electron microscope (x12,000,000 times). From the photograph of FIG. 4, it can be seen that the fibrous carbon nanomaterial according to the present invention has a diameter of 20 to 450 nm, and the developed graphite crystal layer surface is stacked in the form of an accordion, and uniform units of the lamination are formed to show appropriate pores. . It can be seen that the specific surface area measured by the BET method of the prepared fibrous carbon nanomaterial is 114 m 2 / g and has a relatively large specific surface area.

Example 2

4304 mg of fibrous carbon nano material was prepared in the same manner as in Example 1, using the source gas as ethylene instead of carbon monoxide. As a result of observing the fibrous carbon nanomaterial thus prepared with a high resolution transmission electron microscope (× 9,000,000 times), the graphite crystal layer surface having a diameter of 20 to 450 nm and developed as in Example 1 was laminated in the form of accordion, It was confirmed that the unit was opened to form voids. In addition, the specific surface area measured by the BET N ₂ method is 180 m 2 / g, and it can be seen that it has a relatively large specific surface area.

Example 3

1000 mg each of the fibrous carbon nanomaterials prepared according to Examples 1 and 2 was 600 while maintaining a total flow rate of 200 ml / min in a ratio of CO ₂ / Ar (volume ratio 30/70) using a heat treatment furnace of the same type. Activated heat treatment was carried out for 1 hour 30 minutes at ℃. The weight of the activated fibrous carbon nanomaterial was 550 mg, and the burn-off ratio of oxidized and gasified by CO ₂ / Ar gas heat treatment was 45%.

The specific surface of the resultant activated fibrous carbon nanomaterial was measured by BET N ₂ adsorption. As a result, the fibrous carbon nanomaterial of Example 1 was 180 m 2 / g, and the fibrous carbon nano material of Example 2 was 540 m 2 / g. It was confirmed that it has a surface area.

Example 4

1000 mg each of the fibrous carbon nanomaterials prepared according to Examples 1 and 2 was 600 while maintaining a total flow rate of 200 ml / min in a ratio of CO ₂ / Ar (volume ratio 50/50) using a heat treatment furnace of the same type. Activated heat treatment was carried out for 1 hour 30 minutes at ℃. The resulting activated fibrous carbon nanomaterial weighed 450 mg, and the burn-off ratio by heat treatment of CO ₂ / Ar gas was 55%.

The specific surface area of the resultant activated fibrous carbon nanomaterial was measured by BET N ₂ adsorption. As a result, the fibrous carbon nanomaterial of Example 1 was 240 m 2 / g, and the fibrous carbon nano material of Example 2 was 680 m 2 / g. It was confirmed that it has a surface area.

Example 5

The present embodiment relates to an electric double layer charge measurement experiment. In a three-pole system in which a fibrous carbon nanomaterial prepared according to Example 2 is used as an electrode material and an aqueous solution of sulfuric acid solution having a mass ratio of 30% is used as an electrolyte, the cyclic potential scanning method is performed using The amount of charge was measured at a scanning rate of / sec.

The result is called "A", and the charge amount is as shown in FIG.

Example 6

The activated fibrous carbon nanomaterial prepared according to Example 3 has a specific surface area of 540 m 2 / g of ultrafine carbon as an electrode material and a tripolar system having an aqueous solution of sulfuric acid solution having a mass ratio of 30% as an electrolyte. The amount of charge was measured at a scanning rate of / sec.

The result is referred to as 'B', and the charge amount is as shown in FIG.

Example 7

The activated fibrous carbon nanomaterial prepared according to Example 4 had a specific surface area of 680 m 2 / g of ultrafine carbon as an electrode material and an aqueous solution of sulfuric acid solution having a mass ratio of 30% as an electrolyte in a tripolar system. The amount of charge is measured at a scanning rate of / sec.

The result is called "C", and the charge amount is as shown in FIG.

In order to compare with the method according to the present invention, a comparative experiment by various methods was performed.

Comparative Example 1

Molecular sieve carbon materials (Molecularsieving carbons, MSC, Kansai thermal chemistry, Japan; specific surface area: 1220 m 2 / g) instead of fibrous carbon nanomaterials according to the present invention, using 20 전극 / As a result of measuring the charge amount at a scanning speed of sec, the specific amount was 70 F / g.

Comparative Example 2

As a result of measuring the amount of charge at a scanning rate of 20 s / sec using a cyclic potential scanning method in a three-pole system using activated carbon fibers (specific surface area 970 m 2 / g) manufactured from poly acrylonitrile (PAN) as electrodes, Was 85 F / g.

The specific amount measurement results are summarized in Table 1 below.

Kinds Specific surface area (㎡ / g) Specific storage capacity (F / g) Example 5 Carbon Nanofiber A 180 20 Example 6 Activated Carbon Nanofiber B 540 180 Example 7 Activated Carbon Nanofiber C 680 185 Comparative Example 1 Molecular Sieve Granular Activated Carbon 1220 70 Comparative Example 2 PAN based activated carbon fiber 970 85

As can be seen from Table 1, the fibrous carbon nanomaterial of the present invention made from carbon monoxide and various hydrocarbons and its activated heat treatment material have a specific surface area comparable to that of conventional granular activated carbon and activated carbon fibers, and thus have a large specific storage capacity. Shows capacity. In addition, since it is made of a crystalline multilayer carbon layer, it has excellent electrical conductivity and high-speed electric double layer forming ability, and is composed of short fibers so that the ESR of the electrode plate is also lower than that of granular activated carbon.

In addition, since it is manufactured using natural gas and / or hydrocarbon as a raw material, the production cost is low, and excellent workability and excellent cycle stability when making an electrode mixture.

In the case of utilizing the fibrous carbon nanomaterial prepared according to the present invention as an electrode material for a high performance electrochemical capacitor, a material having an electric double layer storage value higher than that of conventional activated carbon and activated carbon fiber having a high manufacturing cost, and having high output characteristics It can manufacture. In addition, since the activated fibrous carbon nanomaterial of the present invention can be produced by a simple process, the manufacturing cost is remarkably low, and the yield is also higher than that of activated carbon prepared from polymer-based and resin-based carbon materials.

Claims (6)

Iron particles prepared by colloidal dispersion and freeze-dried iron oxide (γ-ferrite) having an average particle diameter of 20 to 80 nm and nickel particles prepared by the precipitation method are kneaded at a ratio of iron oxide and nickel particles in a weight ratio of 6/4 to 9/1 (wt / wt). After the reduction treatment in a reducing atmosphere of 400 to 700 ℃, carbon monoxide and / or hydrocarbons as a source gas and mixed with hydrogen on the catalyst surface of the mobile phase and / or fixed bed gas phase decomposition to 500 to 700 ℃ on the catalyst surface A method for producing a fibrous carbon nano material having an accordion type structure, characterized in that for producing. The method of claim 1, wherein the reducing atmosphere is a mixed gas of hydrogen and nitrogen, a mixed gas of hydrogen and argon, or a mixed gas of hydrogen and helium, characterized in that the content of hydrogen in the mixed gas is 2 to 50% by volume. Method for producing a fibrous carbon nano material to be. The method of claim 1, wherein in the source gas, the hydrocarbon is an unsaturated and / or saturated hydrocarbon composed of hydrogen and carbon, acetylene (C ₂ H ₂ ), methane (CH ₄ ), ethylene (C ₂ ) having 1 to 4 carbon atoms H ₄ ), ethane (C ₂ H ₆ ), propylene (C ₃ H ₆ ), propane (C ₃ H ₈ ), butane (C ₄ H ₁₀ ), butylene (C ₄ H ₈ ), butadiene (C ₄ H ₆ ) and one or more selected from the group consisting of isomers thereof, The mixing ratio of the source gas and hydrogen gas is a method of producing a fibrous carbon nano material, characterized in that the ratio of the source gas per volume is preferably 10 to 95%. The method of claim 1, wherein the prepared carbonaceous carbon nanomaterial is further subjected to activation heat treatment to increase the specific surface area. The method of claim 4, wherein the activation heat treatment, characterized in that performed for 10 minutes to 24 hours at 450 to 750 ℃ using a carbon dioxide-inert gas mixture of the mixing ratio 1/9 to 9/1 (vol / vol). Method for producing fibrous carbon nano material. An electrode material for an electrochemical capacitor using fibrous carbon nanomaterials produced by the method of claim 1.