KR20210066054A - Activated carbon for electric double layer capacitor by co2-alkali complex activation process and method for manufacturing the same - Google Patents

Abstract

The present invention relates to activated carbon for an electric double layer capacitor by the activation of a CO_2-alkali complex and a method for manufacturing the same. The present invention provides activated carbon for an electric double layer capacitor in which alkali activation and CO_2 activation are simultaneously performed by activating a carbon material mixed with an alkali activator at a temperature of 900°C. or higher under a CO_2 atmosphere, and a method for manufacturing the same. According to the present invention, micro-pores and meso-pores are simultaneously developed by CO_2-alkali complex activation, which simultaneously proceeds alkali activation (chemical activation) and CO_2 activation (physical activation), so that the electrical properties of the electric double layer capacitor can be improved.

Description

Activated carbon for electric double layer capacitor through CO2-alkali complex activation and method for manufacturing the same

The present invention relates to activated carbon for an electric double layer capacitor and a method for manufacturing the same through _{CO 2 -alkali complex activation, and more particularly, by simultaneously performing alkali activation (chemical activation) and CO 2} activation (physical activation), micropores ( The present invention relates to activated carbon for an electric double layer capacitor through activation of a _{CO 2} -alkali complex, and a method for manufacturing the same, in which micro pores) and meso pores are simultaneously developed to improve the electrical properties of the electric double layer capacitor.

An electric double layer capacitor (EDLC) has a higher energy density than a general battery, a larger capacity per unit volume, and can be rapidly charged/discharged. Accordingly, the electric double layer capacitor (EDLC) is used as a memory backup small power source such as a PC, as well as a power source for an electric vehicle or a hybrid vehicle, and is in high demand in various fields.

In general, in an electric double layer capacitor (EDLC), activated carbon is used as an electrode active material. Activated carbon has a high specific surface area and is useful as an electrode material for an electric double layer capacitor (EDLC). The capacity of the electric double layer capacitor (EDLC) is determined according to the amount of electric charge accumulated in the electric double layer, and the electric charge amount increases as the specific surface area of the electrode increases. Accordingly, since activated carbon has a high specific surface area due to its porous structure, it is possible to increase the electrode capacity and improve the energy density.

Activated carbon is manufactured by obtaining a carbon material obtained by carbonizing a raw material (carbon precursor), such as a plant-based or petroleum-based material, at a high temperature, and then activating the carbon material into a porous structure. At this time, activation is mainly performed by mixing an alkali activator such as potassium hydroxide (KOH) with a carbon material and then heating in an inert gas atmosphere (chemical activation). In this activation process, alkali metals penetrate and react between the carbon crystal layers to form fine pores. For example, Japanese Patent Application Laid-Open No. 2009-260177 and Japanese Patent Application Laid-Open No. 2010-245482, etc. have suggested the above-related techniques.

The pore structure of activated carbon, for example, pore size (diameter) and pore distribution (volume fraction), etc. act as important factors in the electrical properties of an electric double layer capacitor (EDLC). Specific surface area and density may vary depending on the size or distribution of pores, and electrical characteristics such as capacity, resistance, energy density, and output characteristics of an electric double layer capacitor (EDLC) may vary. However, in the conventional activation method, it is difficult to realize good electrical properties because the pore structure is limited.

Japanese Patent Application Laid-Open No. 2009-260177 Japanese Patent Laid-Open No. 2010-245482

Accordingly, an object of the present invention is to provide activated carbon for an electric double layer capacitor and a method for manufacturing the same, in which the pore structure (size and distribution of pores, etc.) of the activated carbon is improved to improve the electrical characteristics of an electric double layer capacitor (EDLC). have.

Specifically, in the present invention, the activation process is monotonous by simultaneously performing the complex activation of a chemical method and a physical method in a single process, and micropores and mesopores are developed at the same time to form an electric double layer capacitor (EDLC). An object of the present invention is to provide an activated carbon for an electric double layer capacitor capable of improving electrical characteristics and a method for manufacturing the same.

In order to achieve the above object, the present invention

A carbon material mixed with an alkali activator is activated under a _{CO 2 atmosphere,}

Provided is an activated carbon for an electric double layer capacitor including micro pores and meso pores.

In addition, the present invention provides a method for producing activated carbon for an electric double-layer capacitor comprising an activation process of simultaneously performing _{alkali activation and CO 2} activation by activating a carbon material mixed with an alkali activator at a temperature of 900° C. or higher under a _{CO 2 atmosphere.} to provide.

According to the present invention, chemical activation and physical activation are simultaneously performed in a single process, so that the activation process is monotonous, and micropores and mesopores are simultaneously developed. Accordingly, the electrical properties of the electric double layer capacitor (EDLC) are improved due to the high specific surface area, low resistance, and appropriate electrode density, as both micropores and mesopores have a high distribution ratio (vol%). have an improving effect.

The term "and/or" as used in the present invention is used to mean including at least one or more of the components listed before and after. As used herein, the term “one or more” refers to one or a plurality of two or more.

The present invention provides activated carbon for an electric double layer capacitor in which a carbon material mixed with an alkali activator is activated _{under a CO 2 atmosphere.} The activated carbon for an electric double layer capacitor according to the present invention has a pore structure in which micro-pores and meso-pores are simultaneously developed _{by chemical activation by an alkali activator and physical activation by CO 2 .}

In the present invention, micropores refer to pores having a size (diameter) of 2 nm or less (ie, ≤ 2 nm) present in activated carbon, and mesopores are the size of pores present in activated carbon. means pores with a size (diameter) greater than 2 nm and less than or equal to 50 nm (ie > 2 nm, ≤ 50 nm). In addition, in the present invention, the macropore (macro pore) refers to the size (diameter) of the pores present in the activated carbon exceeds 50 nm (ie, > 50 nm).

Activated carbon for an electric double layer capacitor according to the present invention _{includes micropores and mesopores simultaneously through the activation of CO 2} -alkali complex, but has an appropriate distribution (volume fraction). In the activated carbon for an electric double layer capacitor according to the present invention, among the total pore volume of the activated carbon, micropores may have 30 vol% or more, and mesopores may have 10 vol% or more. As a specific example, the micropores may have about 30 to 80% by volume, and the mesopores may have about 10 to 30% by volume. And the remaining pore volume may be occupied by macro pores. As described above, when the micropores and the mesopores have volume fractions in an appropriate range, the electrical properties of the electric double layer capacitor (EDLC) may be improved due to a high specific surface area, a low resistance, and an appropriate electrode density.

In addition, the method for producing activated carbon for an electric double layer capacitor according to the present invention includes an _{activation process (CO 2} -alkali complex activation) of activating a carbon material mixed with an alkali activator at a temperature of 900° C. or higher in a _{CO 2 atmosphere.} According to another embodiment, the method for manufacturing activated carbon for an electric double layer capacitor according to the present invention may further include a heat treatment process of heat-treating the activated carbon obtained through _{the CO 2 -alkali complex activation.}

According to a specific embodiment, a method for manufacturing activated carbon for an electric double layer capacitor according to the present invention includes the steps of: (1) preparing a carbon material; (2) a step of obtaining activated carbon in which the carbon material is _{activated by a CO 2 -alkali complex;} (3) a washing/drying process of washing and drying the activated carbon; and (4) a heat treatment process of heat-treating the washed/dried activated carbon. Hereinafter, exemplary embodiments for each process will be described as follows.

(1) carbon material

First, the raw material (carbon precursor) is carbonized.

The raw material is not particularly limited, and may be selected from, for example, plant-based (coconut shell, etc.), petroleum-based and/or coal-based, and the like, and for example, may be selected from plant-based coconut shell and the like.

The above raw materials (coconut shells, etc.) are cut into, for example, particles, dried well, and then carbonized at a temperature of 400°C to 800°C. More specifically, the raw material is carbonized at a temperature of 500 ℃ ~ 700 ℃. The carbonization time is not limited. The carbonization time may depend on the carbonization temperature, which may be, for example, about 10 minutes to 24 hours. The carbonization, for example, may be carried out for 30 minutes to 10 hours at a temperature condition of 500 ℃ ~ 700 ℃. Through this carbonization process, impurities such as volatile matter present in the raw material are removed while carbonizing the raw material (coconut shell, etc.).

In addition, the carbonized carbon material can be pulverized. The carbon material is pulverized to a size of, for example, 50 µm (micrometer) or less. Preferably, it is pulverized to a size of 0.1 to 20 μm, more preferably 5 to 15 μm as a constant size. The grinding method is not particularly limited, and for example, a conventional method such as a ball mill, a rotary mill, and a vibration mill may be used.

(2) activation process

The pulverized carbon material (eg, carbonized coconut shell powder) is activated into a porous material.

At this time, the activation _{proceeds through the CO 2} -alkali complex activation according to the present invention, and specifically, the carbon material mixed with the alkali activator is heat-treated at a temperature of 900° C. or higher under a _{CO 2 atmosphere to activate it.}

According to a more specific embodiment, the pulverized carbon material is mixed with an alkali activator, and the carbon material mixed with the alkali activator is heated in an airtight container (chamber, etc.) in the presence _{of CO 2 to activate alkali (chemical activation).} ) and CO ₂ activation (physical activation) are performed in a single process. Here, the single process means that alkali activation (chemical activation) and CO ₂ activation (physical activation) do not proceed separately, but proceed simultaneously in one sealed container (chamber, etc.). In this CO ₂ -alkali complex activation process, micropores are developed by the alkali activation (chemical activation), and mesopores are developed by the CO ₂ activation (physical activation).

The CO ₂ -alkali complex activation proceeds at a temperature of 900° C. or higher. At this time, if the temperature is too low as less than 900° C., it may be undesirable in physical activation by _{, for example, CO 2 .} Activation may be carried out at a temperature of 900°C to 1,200°C, for example. When the temperature is too high, exceeding 1,200° C., the specific surface area of the activated carbon is reduced, whereby the capacity of the electric double layer capacitor and the like may be lowered. Accordingly, the CO ₂ -alkali complex activation is preferably performed for 30 minutes to 3 hours at a temperature range of 900°C to 1,200°C.

In addition, the alkali activator may be, for example, potassium hydroxide (KOH), sodium hydroxide (NaOH), and/or calcium hydroxide (Ca(OH) ₂ ). The mixing ratio of the carbon material and the alkali activator is not particularly limited, but may be activated by mixing, for example, in a weight ratio of 1: 0.1 to 10 (that is, a weight ratio of pulverized carbon material: activator = 1: 0.1 to 10). can More specifically, it can be activated by mixing in a weight ratio of 1: 0.2 to 5.

Through the above CO ₂ -alkali complex activation, micropores and mesopores are developed simultaneously, but among the total pore volume of the activated carbon, micropores have 30% by volume or more and mesopores have 10% by volume or more. Each volume fraction of these micropores and mesopores can be adjusted by appropriately controlling the activation temperature, the activation time, the mixing ratio with the alkali activator, and/or _{the injection flow rate of CO 2 .}

(3) washing/drying process

The activated carbon obtained through the CO ₂ -alkali complex activation is washed and dried.

The cleaning process is performed to remove impurities present in the activated carbon. The washing process may be selected from, for example, one selected from alkali washing, acid washing and water washing processes, or a combination thereof. It is preferable that the washing process be performed in parallel with alkali washing and acid washing.

In addition, in the washing step, when a metal compound such as KOH is used as the alkali activator in the activation step, the acid is removed at least once or more so that the alkali metal compound (KOH, etc.) is removed along with the removal of impurities present in the raw material. It is preferable to include a washing and water washing process. At this time, as the acid washing liquid, for example, an aqueous acid solution such as hydrochloric acid or sulfuric acid can be used.

After washing as above, moisture present in the activated carbon is removed through drying. Drying is not particularly limited, and, for example, may proceed through hot air drying or natural drying.

(4) heat treatment process

Next, the washed and dried activated carbon is heat-treated. That is, a heat treatment process of heat-treating the washed and dried activated carbon under specific conditions is performed.

According to the embodiment of the present invention, in the production of activated carbon, when the carbon material is subjected to CO ₂ -alkali complex activation as described above and then heat treatment is performed, side reactions (gas generation, etc.) ) and can have excellent electrical conductivity.

Specifically, after washing and drying the activated carbon, heat treatment is performed, but heat treatment is performed at 600 to 900° C. for 10 to 60 minutes. Such heat treatment, for example, may be performed in an inert gas atmosphere such as _{nitrogen (N 2 ) or argon (Ar) gas.}

According to the present invention, as described above _{, when heat-treated in a specific temperature range together with CO 2} -alkali complex activation, activated carbon having a high specific surface area and particularly excellent electrical conductivity can be produced. In addition, the activated carbon prepared as described above has excellent resistance properties, so it is possible to lower the content of the conductive material in the preparation of the activated carbon composition (slurry) for the EDLC electrode, and to increase the content of the activated carbon by that amount, so that it can have a higher capacitance. have. Accordingly, when applied as an EDLC electrode, it is possible to have high output and/or long-term reliability.

As described above, after the heat treatment, the classification process may be further performed according to an exemplary embodiment of the present invention. The classification process is to classify the heat-treated activated carbon and select the activated carbon having a size of 60 μm or less, which can be performed by passing the heat-treated activated carbon through a sieve, for example, to remove particles exceeding 60 μm. have.

More specifically, it is possible to selectively obtain activated carbon of 0.1 ~ 60㎛. Through this classification process, activated carbon of preferably 20 μm or less, more preferably 10 μm or less can be obtained as a final product. According to a specific embodiment, activated carbon having a constant size of 0.5 μm to 10 μm can be obtained as a final product through the classification process. And this activated carbon is used as an electrode material (positive and negative electrode active materials) of EDLC.

Hereinafter, Examples and Comparative Examples of the present invention are exemplified. The following examples are provided only to help the understanding of the present invention, and the technical scope of the present invention is not limited thereby.

[Examples 1 to 4]

First, a carbonized and pulverized coconut shell carbon material was prepared using a coconut shell as a raw material. The prepared coconut shell carbon material was mixed with KOH in a weight ratio of 1:3. Thereafter, the mixture was introduced into the chamber, and then _{heat was applied under a CO 2} atmosphere to simultaneously perform chemical activation and physical activation. At this time, the activation temperature was changed according to each Example. Then, the activated carbon obtained through activation was subjected to acid washing and water washing, and then dried to prepare activated carbon specimens according to each example.

[Comparative Example 1]

Compared with Example 1, in the activation process, only chemical activation using KOH was used as the activated carbon specimen according to this comparative example.

[Comparative Example 2]

As a commercially available product, a YP-50F product prepared by activation with water vapor was purchased and used as an activated carbon specimen according to this comparative example.

For the activated carbon according to each of the Examples and Comparative Examples, properties were evaluated as follows. The results are shown in [Table 1] below.

< Evaluation method >

(1) Specific surface area - _{Measured using the BET method using N 2} adsorption (BEL JAPAN product, model name BEL SORP-MINI Ⅱ measuring instrument in Japan)

(2) Pore structure - After measuring the pore size and distribution using a gas analyzer, BET method, and NLDFT (non-local density functional theory), the volume fraction of micropores and mesopores was evaluated

(3) Static capacitance and resistance - After fabricating an EDLC cell to which activated carbon according to each Example and Comparative Example is applied as an electrode, the capacitance (F/g) and resistance (mΩ) per unit weight at a voltage of 2.7V are measured

< Characteristic evaluation result of activated carbon and EDLC cell > Activation
Way Activation
Temperature specific surface area
[m2/g] V _micro ^{1 )} V _meso ^{2 )} capacitance
[F/g] resistance
[mΩ] Example 1 KOH + CO ₂ 850℃ 2,301 68.9% 22.3% 38.6 12.8 Example 2 KOH + CO ₂ 900℃ 2,435 65.3% 29.8% 40.8 11.4 Example 3 KOH + CO ₂ 950℃ 2,474 63.0% 33.5% 41.2 11.2 Example 4 KOH + CO ₂ 1,250℃ 1,530 75.8% 15.8% 23.7 10.8 Comparative Example 1 KOH 850℃ 2,105 98.2% 1.8% 37.3 13.2 Comparative Example 2 vapor - 1,650 95.0% 5.0% 26.4 15.3 1) V _micro : Volume fraction (%) occupied by micropores among the total pore volume of activated carbon
2) V _meso : Volume fraction (%) occupied by mesopores among the total pore volume of activated carbon

As shown in [Table 1], when only alkali activation was performed (Comparative Example 1), only micropores were developed, but as in Examples, when CO ₂ -alkali complex activation was performed, micropores and mesopores were developed at the same time.

In addition, it was found that the electrical properties of the activated carbon and the EDLC cell were changed according to the activation temperature when the _{CO 2 -alkali complex was activated.} Specifically, it was found that when the activation temperature was too low, the resistance was high, and when the temperature was too high, the capacitance was low. And in the case of complex activation at temperatures of 900 ° C and 950 ° C (Example 2 and Example 3), when only alkali activation was performed (Comparative Example 1) and when only water vapor activation was performed (Comparative Example 2), It was found that excellent results were shown in both resistance and capacitance.

Claims (4)

A carbon material mixed with an alkali activator is activated under a _{CO 2 atmosphere,}
Activated carbon for an electric double layer capacitor, characterized in that it contains micro pores and meso pores.
According to claim 1,
The activated carbon for an electric double layer capacitor, characterized in that, among the total pore volume of the activated carbon, micropores are 30% by volume or more, and mesopores are 10% by volume or more.
A method for producing activated carbon for an electric double-layer capacitor, comprising: activating a carbon material mixed with an alkali activator at a temperature of 900° C. or higher under a _{CO 2 atmosphere, and simultaneously performing alkali activation and CO 2 activation.}
4. The method of claim 3,
The method of manufacturing activated carbon for an electric double-layer capacitor, characterized in that it further comprises a heat treatment step of heat-treating the activated carbon obtained through the activation process at 600 ~ 900 ℃ for 10 minutes to 60 minutes.