KR20080043623A - Preparation method of meso porous activated carbon for supercapacitor electrode - Google Patents

Abstract

A method for preparing activated carbon is provided to increase the content of meso-pores in the activated carbon efficiently, thereby easily attaching electrolytes on a surface of the activated carbon, by chemically activating meso-phase pitch through K2CO3. A meso-phase pitch is pulverized into 10 um or less. The pulverized meso-phase pitch is deposited in a K2CO3 solution of 2-4 M. The deposited meso-phase pitch is dried. The dried meso-phase pitch is heated to a temperature of 700-900°C at a temperature rise rate of 10°C/min or less under an inert gas ambience. The heated meso-phase pitch is washed by water. The washed meso-phase pitch is dried.

Description

Preparation method of activated carbon for supercapacitor electrode with mesopore development {Preparation method of meso porous activated carbon for supercapacitor electrode}

1 is a graph showing pore distribution of activated carbon prepared according to Example 1. FIG.

Figure 2 is a graph showing the pore distribution of activated carbon prepared according to Example 2.

3 is a graph showing the pore distribution of activated carbon prepared according to Example 3.

Figure 4 is a graph showing the pore distribution of activated carbon prepared according to Comparative Example 1.

5 is a graph showing the pore distribution of activated carbon prepared according to Example 4.

The present invention relates to a method for manufacturing activated carbon for a supercapacitor electrode having mesopores, and more specifically, to a mesopore-developed supercapacitor electrode by chemically activating the mesophase pitch using K ₂ CO ₃ as a raw material. It relates to a method of producing activated carbon.

Supercapacitors, unlike batteries that store electrical energy using chemical reactions, are electric energy storage devices that accumulate and store electric charges on the surface of electrodes, and are used as a power source for hybrid vehicles.

As an electrode material of a supercapacitor, metal oxides such as activated carbon, ruthenium oxide, and titanium oxide having a large specific surface area are used, but materials other than carbon electrodes are very expensive, and carbon is generally used the most.

This carbon electrode should generally be porous and have a high specific surface area. On the surface of the porous carbon electrode having a high specific surface area, ions of the electrolyte separated by cations and anions are stored while forming an electric double layer. When electric energy is consumed, the ions are released from the carbon surface and converted into electric energy. In this case, the battery is converted to electrical energy by a chemical reaction, and the number of times of use of the electrode is limited, whereas the supercapacitor generates electrical energy without accompanying a chemical reaction, and thus deterioration according to the number of charge and discharge of the electrode is caused. It is an excellent electrical energy storage device.

However, these supercapacitors contain less energy than batteries. Thus, in order to maintain at least the same energy as the cell, the supercapacitor must occupy a larger volume than the cell.

This improvement requires a high specific surface area carbon electrode to store large amounts of electricity.

It is an activated carbon-based carbon electrode material that can satisfy these characteristics. In particular, a carbon electrode material having a very high carbon purity is required in order to lower electrical resistance.

In general, activated carbon and activated carbon fibers have been widely used as carbon electrode materials.

In the prior art, US Patent No. 5,429,893 discloses that one electrode uses a carbon material and another electrode uses a metal material, which is a redox material, in manufacturing a capacitor, and US Patent No. 5,420,168 describes a resol type. A method for producing carbon foam electrodes of high density and high specific surface area (400-1000 m 2 / g) using resins and other polymers is disclosed.

Also, US Patent No. 5,369,546 discloses a method for manufacturing an electrode in which TiC, Pt, etc. are attached to a composite material of 50% or more of activated carbon and polyacene, and US Patent No. 5,319,518 is a porous and good carbon electrode such as fullerene. A technique for producing an EDLC is disclosed, and US Patent No. 5,172,307 discloses an EDLC electrode manufacturing method in which activated carbon and polyacene are mixed.

In addition, US Patent No. 5,168,433 discloses a method for prolonging the life by attaching acidic functional groups to activated carbon, US Patent No. 5,136,473 has a specific surface area of 1300 m 2 / g by sintering activated carbon having a different particle size A method of manufacturing an electrode is disclosed, and US Patent No. 6,225,020 discloses a method of preparing an electrode by adding RuOx to activated carbon using a sol-gel method. Further, Japanese Laid-Open Patent Publication No. 2002-158140 discloses a method of manufacturing an electrode by attaching various metals to carbon particles.

As described above, the activated carbon used in the prior art has an advantage of low manufacturing cost, but the coal used as a raw material of the activated carbon contains a large amount of impurities, and thus has a disadvantage of increasing resistance when used as an electrode.

The complementary material is activated carbon fiber. Such activated carbon fibers generally have very few inorganic impurities due to the characteristics of the raw materials, and thus hardly generate electrical resistance due to impurities.

Activated carbon and activated carbon fibers for electrodes of supercapacitors must be very fine, unlike activated carbon and activated carbon fibers, which are generally used. At this time, it is known to maintain a high specific surface area.

However, a large specific surface area does not have a high storage capacity, but must have a pore structure through which the electrolyte can sufficiently penetrate into the pores.

Therefore, as activated carbon used as an electrode material, even if activated carbon containing a large amount of micropores and a large specific surface area is difficult to infiltrate into the micropores, it is very important to increase the content of mesopores.

An object of the present invention is to provide an activated carbon for a supercapacitor electrode having mesopores so that the electrolyte can be easily attached to the carbon surface by chemically activating the mesophase pitch using K ₂ CO ₃ as a raw material.

Activated carbon for supercapacitor electrode with mesopores according to the present invention for achieving the above object is a step of grinding the mesophase pitch to 10㎛ or less and immersing it in 2-4M K ₂ CO ₃ solution, 2 Drying the mesophase pitch immersed in a -4M K ₂ CO ₃ solution and heating the dried mesophase pitch to 700-900 ° C. at an elevated temperature of 10 ° C./min or less in an inert gas atmosphere. Characterized in that it comprises a.

Hereinafter, the present invention will be described in detail.

The present invention relates to a method for producing activated carbon for supercapacitor electrodes in which mesopores are developed by chemically activating the mesophase pitch prepared from coal or petroleum pitch using K ₂ CO ₃ as a raw material.

The mesophase pitch used as a raw material in the present invention is preferably obtained by obtaining a uniform and fine particles, and pulverized to a diameter of 10 ㎛ or less for the convenience of the process of processing activated carbon fibers into electrodes.

Then, the pulverized mesophase pitch is immersed in a 2-4M K ₂ CO ₃ solution, and then left to dry for a period of time. Deposition time may be in the range 1-20 hours, but not limited to. Through this process, the mesophase pitch powder is recovered with the K ₂ CO ₃ component attached to the inside and the surface of the carbon. In this case, when the concentration of the K ₂ CO ₃ solution is 2M or less, the degree of chemical activation progress of mesophase pitch may not occur sufficiently, and when it exceeds 4M, the specific surface area of the mesophase pitch particles no longer increases significantly. The physical properties as an electrode material do not increase significantly, which is uneconomical.

Then, the dried mesophase pitch is heated by heating to 700-900 ° C. under inert gas atmosphere. The reason for heat treatment in an inert gas atmosphere is to prevent the sample from being oxidized and extinguished. In this case, when the temperature is 700 ° C. or lower, the specific surface area does not appear high. When the temperature is 900 ° C. or higher, the yield decreases. This happens so badly that using above this temperature is not economical. At this time, the heating time is not limited to this, but preferably 30 to 60 minutes.

In addition, the temperature increase rate during the heat treatment is 10 ℃ / min or less. If the temperature increase rate is 10 ℃ / min or more mesopores do not develop the content of mesopores may be reduced. The temperature increase rate during the heat treatment is not limited thereto, but preferably 5-8 ° C./min.

In addition, it is preferable to include the step of washing the heat treated mesophase pitch with water and dried. This washing and drying process may be repeated several times, and the repeated washing and drying process sufficiently removes the remaining K ₂ CO ₃ component.

Hereinafter, the present invention will be described with reference to Examples, which are examples of the present invention, and are not intended to limit the present invention.

Example  One

The mesophase pitch was pulverized to 10 micrometers or less, which was then immersed in a 4 mole solution of K ₂ CO ₃ for 1 hour, heated to evaporate water, and the remaining sample was activated by heat treatment at 700 ° C. for 1 hour in a nitrogen atmosphere. The temperature increase rate for this was 15 degreeC / min. Then, it was recovered, washed sufficiently with water and dried to prepare activated carbon. As a result of measuring the specific surface area of the prepared activated carbon sample, the pore distribution was as shown in Fig. 1, and the average pore size was 57.6 mm 3.

Example  2

The same sample as in Example 1 was immersed in a 4 mol K ₂ CO ₃ solution for 1 hour and then heated to evaporate water, and the remaining sample was activated by heat treatment at 700 ° C. for 1 hour in a nitrogen atmosphere, and the temperature rising rate was 10 ° C./min. It was. Then, it was recovered, washed sufficiently with water and dried to prepare activated carbon. As a result of measuring the specific surface area of the prepared activated carbon sample of the prepared activated carbon sample, the pore distribution was as shown in FIG. 2 and the average pore size was 61.2 mm 3. Compared to Example 1, the mesopores were much increased.

Example  3

Using the same sample as in Example 1, 4 mol K ₂ CO _{3 was} deposited for 1 hour, heated to evaporate water, and the remaining sample was activated by heat treatment at 700 ° C. for 1 hour in a nitrogen atmosphere, and the temperature rising rate was 8 ° C./min. It was. Then, it was recovered, washed sufficiently with water and dried to prepare activated carbon. As a result of measuring the specific surface area of the prepared activated carbon sample, the average pore size was 63.2Å, the pore distribution was as shown in Fig. 3, mesopores were increased compared to Fig. 1, especially mesopores near 50-100Å Developed.

Comparative example  One

Using the same sample as in Example 1, 3 mol K ₂ CO _{3 was} immersed in 1 hour and then heated to evaporate water, and the remaining sample was activated by heat treatment at 800 ° C. for 1 hour in a nitrogen atmosphere, and the temperature rising rate was 15 ° C./min. It was made. Then, it was recovered, washed sufficiently with water and dried to prepare activated carbon. As a result of measuring the specific surface area of the prepared activated carbon sample, the average pore size was 51.9 mm 3, and the pore distribution was as shown in FIG. 4.

Example  4

Using the same sample as in Example 1, 3 mol K ₂ CO _{3 was} deposited for 1 hour, heated to evaporate water, and the remaining sample was activated by heat treatment at 800 ° C. for 1 hour in a nitrogen atmosphere, and the temperature rising rate was 8 ° C./min. It was. Then, it was recovered, washed sufficiently with water and dried to prepare activated carbon. As a result of measuring the specific surface area of the prepared activated carbon sample, the average pore size was 64 μs, the pore distribution was as shown in FIG. 5, and it showed that mesopores around 30-50 μm developed very uniformly compared to Comparative Example 1. .

As can be seen from the above embodiment, it can be seen that the activated carbon for the electrode for the supercapacitor prepared according to the present invention increases the content of mesopores and increases the particle size of the average pore.

Activated carbon for the electrode for the supercapacitor prepared according to the present invention has the characteristic that the mesopore content of the size of easy penetration of the electrolyte is increased.

Claims (3)

In the method for producing activated carbon for supercapacitor electrodes using mesophase pitch as a raw material, Grinding mesophase pitch to 10 μm or less and immersing it in a 2-4M K ₂ CO ₃ solution; Drying the mesoface pitch immersed in a 2-4M K ₂ CO ₃ solution; And Heat treating the dried mesophase pitch to 700-900 ° C. at an elevated temperature of 10 ° C./min or less in an inert gas atmosphere; Method for producing activated carbon for a supercapacitor electrode comprising a. The method of manufacturing activated carbon for a supercapacitor electrode according to claim 1, wherein the temperature increase rate during the heat treatment is 5-8 ° C / min. The method of claim 1, further comprising the step of washing the heat treated mesophase pitch with water and drying the activated carbon for the supercapacitor electrode.

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