KR20150132710A - Method for improving power property of active carbon using coke materials - Google Patents

Abstract

The present invention relates to a method for improving output properties of an energy storage device such as an electric double-layer capacitor (EDLC) or the like through control for the particle size of activated carbon using cokes as raw materials. The method for improving output properties of activated carbon using cokes as raw materials comprises: a carbonizing step for carbonizing the cokes at a temperature of 400 to 800°C; a grinding step for grinding the carbonized cokes; an activating step for mixing the ground cokes and an activating agent, and heating the same at 400 to 1200°C to be activated; a cleaning/drying step for cleaning and drying the cokes activated carbon; and a particle control step for grinding the cleaned and dried cokes activated carbon to have an average particle size of 3 to 7 μm. According to the present invention, the method of the present invention is provided to manufacture activated carbon by using the cokes as raw materials, and controls the distribution of particle sizes to be low, thus the tap density and output properties can be improved.

Description

TECHNICAL FIELD [0001] The present invention relates to a method of improving output characteristics by controlling the particle size of activated carbon made from coke,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for improving the output characteristics of an energy storage device such as an electric double layer capacitor (EDLC) by controlling the particle size of activated carbon made of coke as a raw material. More specifically, The present invention relates to a method of improving output characteristics by controlling particle size of activated carbon, which can improve tap density and output characteristics by controlling the particle size distribution of activated carbon to be low .

Activated carbon is widely used as an electrode material for electric double layer capacitors (EDLC) and lithium secondary batteries. Particularly, activated carbon for an electrode of an electric double layer capacitor (EDLC), which is widely used as a hybrid car or a backup power source for a storage element, requires a porous activated carbon having a large specific surface area in order to increase the energy density, have.

Generally, activated carbon is produced by carbonizing (calcining) a carbon raw material at a temperature of 500 ° C or higher, and then activating it with a porous structure. At this time, in the activation step, an alkaline activator such as potassium hydroxide (KOH) is mainly mixed with the carbon raw material and then heated in an inert gas atmosphere at about 500 to 1200 ° C to allow the alkali metal to penetrate into the carbon crystal layer So that micropores are formed. The activated carbon obtained by such alkali activation has a large specific surface area and uniform particle size, and is thus usefully used for an electrode of an electric double layer capacitor (EDLC).

Activated carbon is widely used as an electrode for electric double layer capacitors (EDLC) in which a phenolic resin is activated as a carbon source and a coconut shell, apricot seeds and rice husk are activated. For example, Korean Patent No. 10-0348499 discloses a method for producing activated carbon using rice hulls, and Korean Patent No. 10-0342069 discloses a method of mixing a binder and the like in rice hull activated carbon, A method of manufacturing an electrode is disclosed.

However, activated carbon produced by using phenol resin as a carbon raw material (starting material) has a low content of impurities and low resistance characteristics. In the case of activated carbon produced from coconut shells, apricot seeds and rice hulls, the resistance characteristics are relatively good compared to the phenolic resin, but this also shows a low resistance characteristic, which is also due to the capacitance per unit volume (F / cc) Is small.

Accordingly, in manufacturing an electrode for an electric double layer capacitor (EDLC), a conductive material is added to activated carbon. Specifically, an electrode for an electric double layer capacitor (EDLC) is manufactured by rolling an activated carbon composition (slurry) obtained by mixing activated carbon, a binder and a conductive material. The binder is mainly composed of polytetrafluoroethylene (PTFE), carboxymethylcellulose (CMC), polyvinylpyrrolidone (PVP) or the like. The conductive material is mainly carbon black.

At this time, in general, the conductive agent is contained in an amount of 14 to 20% by weight to improve resistance characteristics. The greater the amount of the conductive material to be added is, the more the electric conductivity is improved and the resistance characteristic can be improved. However, the activated carbon composition for electrodes according to the related art has a problem that the content of the conductive material is too large, and the content of the activated carbon becomes relatively small, thereby decreasing the electrostatic capacity.

On the other hand, cokes, which is a by-product of refining generated in the refining process of petroleum, are not used as carbon raw materials and are not produced as activated carbon for electric double layer capacitors (EDLC). In the case of producing activated carbon using coke as a raw material, the specific surface area that directly affects the capacity of the electric double layer capacitor (EDLC) can not be increased. Activated carbon produced from coke as a raw material has a low tap density. As a result, when an electrode such as an electric double layer capacitor (EDLC) is applied, the output characteristic is deteriorated.

Korean Patent No. 10-0348499 Korean Patent No. 10-0342069

Accordingly, the present invention relates to a process for producing activated carbon using cokes as a carbon raw material, and controlling the particle size distribution of the activated carbon to improve the tap density and the output characteristics by controlling the particle size of activated carbon made of coke as a raw material And to provide a method for improving the output characteristic through the use of the light source.

According to an aspect of the present invention,

A carbonization step of carbonizing the coke at a temperature of 400 ° C to 800 ° C;

A pulverizing step of pulverizing the carbonized coke;

An activation step of mixing the pulverized coke with an activating agent and then activating the mixture by heating to 400 to 1,200 ° C;

A cleaning / drying step of cleaning and drying the activated coke activated carbon; And

And a particle size controlling step of crushing the washed and dried coke activated carbon to have an average particle size of 3 탆 to 7 탆. The present invention also provides a method for improving the output characteristics of activated carbon using coke.

The method may further include a step of heating the coke activated carbon to remove the surface functional group, which is performed between the washing / drying process and the particle size control process or after the particle size control process.

In addition, it is preferable that the activation step uses an alkali salt as an activator, and the pulverized coke and an alkali salt are used at a weight ratio of 1: 2.0 to 1: 3.0.

According to the present invention, active carbon is produced using cokes as a carbon source, and the particle size distribution is controlled to be low, thereby improving the tap density and output characteristics.

FIG. 1 is a graph showing the results of measurement of pore distribution of activated carbon prepared according to an embodiment.
2 shows the capacity retention rate with time.
FIG. 3 shows the resistance increase rate with time.

Hereinafter, the present invention will be described in detail.

The present invention provides a method for producing activated carbon using cokes as a carbon raw material (starting material), more specifically, a method for improving output characteristics by controlling the particle size of activated carbon made from coke. The activated carbon produced according to the present invention is used as an electrode of an energy storage device such as an electric double layer capacitor (EDLC) or a lithium secondary battery, and is particularly useful as an electrode of an electric double layer capacitor (hereinafter abbreviated as EDLC) do.

(1) a carbonization process for carbonizing the coke; (2) a crushing process for crushing the carbonized coke; (3) an activation process for activating the crushed coke; (4) a cleaning / drying process for cleaning and drying the activated coke activated carbon, and (5) a particle size control process for controlling the particle size by pulverizing the washed and dried coke activated carbon. Further, the method may further include a surface functional group removing step of performing surface treatment between the washing / drying step and the particle size adjusting step or after the particle size adjusting step, by heat treating the coke activated carbon. Each process will be described as follows.

(1) Carbonization process

First, carbonize the coke. At this time, the coke used as the starting material is not limited, and it is preferably selected from petroleum coke which is a by-product generated in the refinery process (petroleum refining process).

The above-mentioned coke is sampled, for example, in the form of particles, and carbonized (first sintering) at a temperature of 400 ° C to 800 ° C. More specifically, carbonization is carried out at a temperature of 500 ° C to 700 ° C. The carbonization time is not limited. The carbonization time can depend on the carbonization temperature, and can be, for example, about 10 minutes to 24 hours. The carbonization time can be, for example, 30 minutes to 10 hours at a temperature condition of 500 ° C to 700 ° C. Through this carbonization process, impurities such as volatile matter present in the raw material are removed while carbonizing the coke.

(2) Grinding process

The carbonized coke is pulverized. The carbonized coke is crushed to a size of, for example, 200 mu m (micrometer) or less. Preferably, it is pulverized to a size of about 50 to 200 mu m as a uniform size. The pulverization method is not particularly limited and can be carried out by a conventional method such as a ball mill, a rotary mill and a vibration mill.

(3) Activation process

The pulverized coke powder is activated by a porous material. Specifically, the pulverized coke powder is mixed with an activator, and then heated to 400 ° C to 1,200 ° C (second calcination). At this time, the activation temperature is preferably 500 占 폚 or higher, and more preferably 600 占 폚. More specifically, the activation temperature preferably proceeds in a temperature range of 600 to 1,000 ° C. The activation time, that is, the time for heating after mixing with the activator is not limited. The activation time may depend on the activation temperature, and may be, for example, about 10 minutes to 5 hours. The activation time may be, for example, 30 minutes to 3 hours at a temperature of 600 to 1,000 DEG C, for example. By this activation process, the coke powder is reformed into a porous formed with a large number of pores.

The activator is not limited. The activator should be capable of increasing the specific surface area by modifying the coke to be porous. The activating agent may be selected from alkali salts (alkali metal compounds) and the like, preferably one or more selected from potassium hydroxide (KOH) and sodium hydroxide (NaOH).

In the activation step, the mixing ratio of the pulverized coke powder and the activator is not particularly limited. For example, the weight ratio of the pulverized coke powder: activator = 1: 0.1 to 1:10, 10 by weight). Preferably in a weight ratio of 1: 2.0 to 1: 3.0.

(4) Cleaning / drying process

The activated coke activated carbon is washed and dried.

The cleaning process proceeds to remove impurities present in the coke activated carbon. The cleaning process may be selected from, for example, one selected from the group consisting of alkali cleaning and acid cleaning, or a combination thereof. It is preferable that the cleaning process is performed in parallel with the alkali cleaning and the acid cleaning. Further, in the cleaning step, when the alkali metal compound (KOH or the like) is used as the activating agent in the activation step, at least the acid cleaning is performed so as to remove the alkali metal compound (KOH, etc.) . At this time, an acid aqueous solution such as hydrochloric acid or sulfuric acid can be used as the pickling solution.

After the washing as described above, the water present in the coke activated carbon is removed through drying. The drying is not particularly limited, and can be carried out, for example, by hot air drying or natural drying.

(5) Particle size control process

Next, the cleaned and dried coke activated carbon is pulverized to adjust the particle size. At this time, the particle size control is carried out such that the average particle size of the cleaned and dried coke activated carbon is 3 탆 to 7 탆. More specifically, the cleaned and dried coke activated carbon is finely pulverized and classified through classification to have an average particle size of 3 탆 to 7 탆. At this time, classification can proceed by passing through a sieve. When the particle size distribution has such a proper size, the tap density is increased and the output characteristics are improved.

(6) Surface Functional group  Removal process

Further, in accordance with an alternative embodiment of the present invention, there is provided a process for producing a coke-like activated carbon, which is carried out between (4) the cleaning / drying step and (5) The surface functional group removing step for removing the surface functional group can be performed.

At this time, the surface functional group removing process proceeds through heat treatment. The surface functional group removing step can be carried out at a temperature of, for example, 600 ° C to 800 ° C. More specifically, it can be heat-treated at a temperature of 600 ° C to 800 ° C, for example, for 10 minutes to 5 hours in an inert atmosphere such as nitrogen (N ₂ ) or argon (Ar) Through such a surface functional group removing step, the oxygen functional groups existing on the surface of the coke activated carbon may be removed.

Hereinafter, embodiments of the present invention will be exemplified. The following examples are provided to aid understanding of the present invention, and thus the technical scope of the present invention is not limited thereto.

[Example]

1. Activated carbon Manufacturing example

Activated carbon was prepared by the following process using petroleum coke generated in the refining process of petroleum.

<Carbonization step>

First, petroleum coke was charged into a heating furnace, then heated at a heating rate of 10 ° C / min and carbonized at a temperature of about 550 ° C for 3 hours.

<Crushing>

The carbonized coke was put into a ball mill pulverizer to have a particle size distribution of 60 mu m or less.

<Activation>

The pulverized coke powder was mixed with KOH (activating agent), which was then added by heating. At this time, the crushed coke powder and KOH (activator) were varied in weight ratio according to each test piece as shown in Table 1 below. Then, the furnace was heated at a heating rate of 10 ° C / min and activated at a temperature of about 680 ° C for 1 hour and 30 minutes under a nitrogen gas atmosphere.

<Cleaning and drying>

The activated coke activated carbon powder was washed three times with an aqueous hydrochloric acid solution and washed with water, followed by hot air drying.

&Lt; Surface functional group removal >

The washed and dried coke activated carbon powder was put into a heating furnace, and then heated at a heating rate of 10 ° C / min and heat-treated for 1 hour. At this time, the heat treatment temperature was varied for each specimen. Specifically, the heat treatment was carried out at 650 ° C in increments of 5 ° C, and was different for each test piece.

<Classification>

The heat-treated coke activated carbon was passed through a sieve and used with different average particle sizes according to each specimen.

2. EDLC  device Manufacturing example

Activated carbon, a binder and a conductive material were put in a stirring vessel and then stirred to prepare an active carbon composition in slurry form. At this time, the activated carbon according to each of the specimens prepared above was used. The binder used was a mixture of polytetrafluoroethylene (PTFE), carboxymethylcellulose (CMC), styrene-butadiene rubber (SBR), and polyvinylpyrrolidone (PVP). Carbon black was used as the conductive material. At this time, the activated carbon composition (slurry) was set to a total weight (100 wt%) and the binder was 3.0 wt% of PTFE, 1.6 wt% of CMC, 3.0 wt% of SBR and 0.4 wt% of PVP, (Carbon black).

The activated carbon composition (slurry) according to each of the specimens was pressed by a roller press to obtain an electrode sheet having a thickness of about 150 mu m. Next, each of the electrode sheets was cut into a disk shape, and a coin-shaped EDLC was produced in the same manner as usual.

The electrical characteristics of the coin type EDLC according to each of the specimens prepared above were evaluated.

(1) Characterization of activated carbon according to weight ratio of activator

In preparing the activated carbon as described above, the weight ratio of the activator was varied according to each specimen. The specific surface area and the content of the metal impurity of each activated carbon were evaluated as shown in Table 1 below. As shown in Table 1 below, when the activator was used in a weight ratio of 1: 2.6, the best results were obtained considering both the specific surface area and the content of metal impurities. In Table 1 below, ND is not detected.

&Lt; Specific Surface Area of Activated Carbon and Evaluation Results of Metal Impurities According to Weight Ratio of Activator > Activator weight ratio
Specific surface area
(M &lt; 2 &gt; / g)
Metal impurity (ppm)
K Fe Ni Cu Cr Cl Na Total 1: 2.0 1,640 259 63 2 ND 1.5 5 ND 320.5 1: 2.3 1,700 275 68 1.8 1.1 0.8 4.4 ND 331.1 1: 2.6 1,900 290 61 2.2 1.2 0.6 5.8 ND 340.8 1: 3.0 2,050 380 59 2.8 0.5 0.6 4.5 ND 427.4

In addition, pore distribution characteristics of the activated carbon prepared by using the activator in the weight ratio of 1: 2.6 were confirmed. This is shown in FIG. As shown in FIG. 1, it was found that 95% or more of the pore distribution was distributed in the range of 6 Å to 30 Å (0.6 nm to 3.0 nm).

(2) Characteristic evaluation by removal of surface functional group

In order to effectively reduce the oxygen functional groups having a close relationship with the long-term reliability, particularly the capacity retention rate, the experiment according to the heat treatment temperature was carried out as described above. That is, the content of oxygen functional groups changed according to the heat treatment temperature was measured. The results are shown in Table 2 below.

&Lt; Evaluation results of physical properties and electrical characteristics of other activated carbon for heat treatment >
Heat treatment temperature
Oxygen function
(meg / g)
Specific surface area
(M &lt; 2 &gt; / g)
Long term reliability result (Φ1840 standard) - 1,000hr test Volume
(F / g) resistance
(mΩ) Capacity retention rate
(%) Resistance increase rate
(%) CEP 0.62 2,000 29.9 7.82 82.9 139.1 CEP HT1 0.44 1,840 28.3 8.04 86.0 138.9 CEP HT2 0.39 1,760 27.9 8.31 87.1 135.3 CEP HT3 0.30 1,460 23.5 9.14 86.5 136.1

As shown in [Table 2], it was confirmed that the oxygen functional group content decreased with increasing the heat treatment temperature, and the long-term reliability evaluation data was also improved by the decrease of the functional group. However, if the heat treatment temperature is excessively increased, the specific surface area decreases, and accordingly the capacity tends to decrease. In this experiment, it was found that CEP HT1 showed the best results. 2 and 3 show the capacity retention rate (FIG. 2) and the rate of resistance increase (FIG. 3) over time. In Figs. 2 and 3, YP is a specimen using conventional conventional activated carbon.

(3) Evaluation of tap density output characteristics by particle size adjustment

Experiments on the improvement of the tap density and the improvement of the output characteristics were carried out by adjusting the particle size of the activated carbon. At this time, activated carbon having an average particle size distribution of 5 mu m and activated carbon having an average particle size distribution of 8 mu m were used as specimens. Table 3 below shows the results of measuring the tap density of each specimen.

The capacity and output characteristics of the device to which activated carbon according to each of the above specimens was applied were evaluated, and the results are shown in Table 4 below.

         <Tap density measurement result> Remarks Activated carbon particle size Tap density Psalm 1 5 μm average particle size 0.373 g / ml Psalm 2 8 μm average particle size 0.332 g / ml

&Lt; Capacity and output characteristics evaluation result > Remarks
Capacity (F) Print
(800 / 4mA) 4mA 40mA 800mA 2.7V
8 탆 4.24 3.27 3.43 80.9% 5 탆 3.60 2.73 2.95 82.1% 1.0M TEABF ⁴ / ACN

As shown in [Table 3] and [Table 4], when the particle size was as low as 5 mu m, it was found that the Tap density was improved and the capacity and output characteristics were effectively improved.

Claims (3)

A carbonization step of carbonizing the coke at a temperature of 400 ° C to 800 ° C;
A pulverizing step of pulverizing the carbonized coke;
An activation step of mixing the pulverized coke with an activating agent and then activating the mixture by heating to 400 to 1,200 ° C;
A cleaning / drying step of cleaning and drying the activated coke activated carbon; And
And a particle size controlling step of crushing the washed and dried coke activated carbon to have an average particle size of 3 to 7 占 퐉.
The method according to claim 1,
The method as claimed in claim 1, further comprising the step of heating the coke activated carbon to remove the surface functional groups during the washing / drying process and the particle size control process or after the particle size control process, Of the output characteristic of the output signal.
The method according to claim 1,
Wherein the activating step uses an alkali salt as an activator, and activating the coke by using the ground coke and an alkali salt in a weight ratio of 1: 2.0 to 1: 3.0.

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