KR102608029B1 - Method for preparation of high crystalline artificial graphite from hard carbon and artificial graphite by the same - Google Patents

Abstract

The present invention relates to a method of producing highly crystalline artificial graphite from non-graphitizable carbon and to artificial graphite produced thereby. Compared to the conventional method of producing artificial graphite, it does not use a halogen metal or halogen compound and is treated at high temperature. It also provides a method of obtaining highly crystalline artificial graphite through a simple process using non-graphitizable carbon, which cannot have a highly crystalline graphite structure.

Description

Method for producing highly crystalline artificial graphite from non-graphitized carbon and artificial graphite produced thereby {METHOD FOR PREPARATION OF HIGH CRYSTALLINE ARTIFICIAL GRAPHITE FROM HARD CARBON AND ARTIFICIAL GRAPHITE BY THE SAME}

The present invention relates to a method for producing highly crystalline artificial graphite from non-graphitizable carbon and to artificial graphite produced thereby. More specifically, the present invention relates to non-graphitizable carbon such as carbon black, activated carbon, isotropic carbon fiber, etc., and silicon precursor as raw materials. It is possible to improve the quality of the material by manufacturing highly crystalline artificial graphite using a method of manufacturing artificial graphite that has higher crystallinity and is free of impurities than conventional artificial graphite, and does not require a catalyst removal process, and the artificial graphite produced thereby It's about.

Artificial graphite is a carbon material made up of graphene, a two-dimensional flat crystal structure, that has high thermal and electrical conductivity and excellent mechanical properties. In addition, artificial graphite has excellent thermal and chemical stability and is used for various purposes such as electrical devices, batteries, fuel cells, and fire-resistant materials. In order to improve the electrical and thermal conductivity of artificial graphite, the crystallinity of artificial graphite must be high and it must have a defect-free structure.

A common method for producing artificial graphite is to produce coke from petroleum or coal-based pitch and carbonize and graphitize it. In order to improve crystallinity and reduce defects in the artificial graphite manufacturing process, it is necessary to form anisotropic crystals from the manufacturing stage of the raw material pitch. More specifically, orientation must be provided during the pitch manufacturing process to produce anisotropic pitch, which is easily graphitized carbon, and anisotropic coke must be manufactured from this. High crystalline artificial graphite can be produced by graphitizing the produced anisotropic coke at a temperature of 2700°C or higher. In particular, in order to produce highly crystalline artificial graphite, catalysts such as AlCl ₃ and BF ₃ must be used. In the case of AlCl ₃ , Al remains as an impurity during the artificial graphite manufacturing process, so an acid treatment process and a high purification process are required to remove it. Additionally, there is a risk that halogen elements may be released and corrode experimental equipment.

Meanwhile, carbon materials such as carbon black, activated carbon, and isotropic carbon fiber are non-graphitizable carbon that does not graphitize even at high temperatures above 2700°C. This non-graphitizable carbon does not form graphite crystals at high temperatures and has many defects, so its electrical and thermal conductivity are lower than that of artificial graphite. Therefore, in order to improve the performance and increase the value of non-graphitizable carbon, it is necessary to graphitize it and improve its crystallinity.

Therefore, in order to induce high value addition of non-graphitizable carbon, it is necessary to manufacture artificial graphite from non-graphitizable carbon, and in order to utilize the method industrially, simplification and simplification of the manufacturing process for mass production are necessary.

Accordingly, the present invention aims to provide a method for producing highly crystalline artificial graphite from non-graphitizable carbon. More specifically, the aim is to provide a method of producing high-quality artificial graphite from non-graphitizable carbon by reducing defects in artificial graphite and increasing crystallinity.

However, the technical problem to be achieved by the present invention is not limited to the technical problem mentioned above, and other technical problems not mentioned will be clearly understood by those skilled in the art from the description below. It could be.

As a technical means for achieving the above-described technical problem, one aspect of the present invention is,

A method for producing artificial graphite, comprising: a first step of mixing non-graphitizable carbon and a silicon precursor; A second step of heat treating the mixture formed in the first step to form silicon carbide; A third step of heat treating the formed silicon carbide in an air atmosphere to remove unreacted non-graphitized carbon; and a fourth step of producing highly crystalline artificial graphite by graphitizing the heat-treated silicon carbide.

The non-graphitizable carbon may be selected from the group consisting of carbon black, activated carbon, isotropic carbon fiber, and mixtures thereof.

The silicon precursor may be selected from the group consisting of silicone, silicone oil, silica, and mixtures thereof.

The mixing ratio of the non-graphitizable carbon and the silicon precursor may be characterized in that the molar ratio is 1:0.1 to 1:1.5.

The heat treatment in the second step may be performed in an inert gas atmosphere at a temperature of 1200°C to 2100°C for 30 to 180 minutes.

The third step of heat treatment may be performed in an oxygen-containing atmosphere at a temperature of 300°C to 800°C for 60 to 300 minutes.

The fourth step of graphitization may be characterized by heat treating the heat-treated silicon carbide in an inert gas atmosphere at a temperature of 2400°C to 3000°C for 30 to 180 minutes.

The method for producing highly crystalline artificial graphite may be characterized by not using a halogen compound.

The highly crystalline artificial graphite may be characterized in that the interlayer distance is 0.34 nm or less.

It may be characterized in that the peak intensity ratio (I _d /I _g ) of the peak for defects (I _d ) and the crystalline peak (I _g ) as measured by the Raman spectrum of the highly crystalline artificial graphite is 0.05 or less.

Another aspect of the present invention is,

A highly crystalline artificial graphite made of a mixture of non-graphitizable carbon and a silicon precursor, wherein the non-graphitizable carbon is selected from the group consisting of carbon black, activated carbon, isotropic carbon fiber, and mixtures thereof, and the silicon precursor is silicon, silicon Provided is highly crystalline artificial graphite selected from the group consisting of oil, silica, and mixtures thereof.

The highly crystalline artificial graphite may be characterized in that the interlayer distance is 0.34 nm or less.

It may be characterized in that the peak intensity ratio (I _d /I _g ) of the peak for defects (I _d ) and the crystalline peak (I _g ) as measured by the Raman spectrum of the highly crystalline artificial graphite is 0.05 or less.

According to one aspect of the present invention, the crystallinity of non-graphitizable carbon can be improved by manufacturing it using non-graphitizable carbon as a carbon precursor. In addition, this is not limited to non-graphitized carbon and can be applied to all carbon materials that can be used as carbon precursors. In particular, it can be applied to carbon material waste with high chemical and thermal stability, thereby solving the problem of carbon material waste disposal. There will be. Additionally, the process is simple, making it possible to present a method suitable for mass production.

The effects of the present invention are not limited to the effects described above, and should be understood to include all effects that can be inferred from the configuration of the invention described in the detailed description or claims of the present invention.

Figure 1 is a flowchart showing a method for manufacturing artificial graphite according to an example.
Figure 2 shows the results of X-ray gray matter analysis after the second step in the manufacturing method according to Example 1, Example 2, Example 3, Example 4, and Comparative Example 1 according to the present invention.
Figure 3 shows the results of X-ray gray matter analysis after the third step in the manufacturing method according to Example 1, Example 2, Example 3, Example 4, and Comparative Example 1 according to the present invention.
Figure 4 shows the results of X-ray gray matter analysis after the fourth step in the manufacturing method according to Example 1, Example 2, Example 3, Example 4, and Comparative Example 1 according to the present invention.
Figure 5 shows the Raman analysis results of artificial graphite prepared from Example 1, Example 2, Example 3, Example 4, and Comparative Example 1.
Figure 6 shows SEM images of artificial graphite prepared from Example 1, Example 2, Example 3, Example 4, and Comparative Example 1.
Figure 7 shows TEM images of artificial graphite prepared from Example 1, Example 2, Example 3, Example 4, and Comparative Example 1.
Figure 8 shows the electrical conductivity measurement results of artificial graphite prepared from Example 1, Example 2, Example 3, Example 4, and Comparative Example 1.

Hereinafter, the present invention will be described in more detail. However, the present invention can be implemented in various different forms, and the present invention is not limited to the embodiments described herein, and the present invention is only defined by the claims to be described later.

In addition, the terms used in the present invention are only used to describe specific embodiments and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly dictates otherwise. In the entire specification of the present invention, 'including' a certain element means that other elements may be further included rather than excluding other elements, unless specifically stated to the contrary.

Necessity of manufacturing artificial graphite

Graphite is a structure in which carbon is arranged in a hexagonal network, layer by layer, and combined. It has good thermal and electrical conduction properties, high temperature stability, and good lubrication. In addition, it is possible to select electrical conductivity between carbonaceous and graphite and has low thermal expansion rate and low vapor pressure. Graphite is formed as a hexagonal crystal, and the bonds between carbons are covalent bonds, and the gap is 1.418Å. In addition, the bond between layers forms a van der Waals bond, the spacing is c/2 = 3.347Å, unit cell: a = b = 2.456Å, c = 6.694Å, bond energy in base plain (a-b direction): about 524kJ/mol , Binding energy between base plain and base plain (c direction): 7kJ/mol.

A single crystal shows anisotropy in its own structure and is almost isotropic in the base plane, but it varies depending on the lattice distance in the C direction. It is light and easy to handle, and its strength increases in proportion to temperature. Additionally, it is easy to machine (graphite). In addition, it is chemically corrosion resistant and has excellent wear resistance. However, it does not wet and does not adhere to most molten metals or slag.

The thermal expansion of graphite has a small range, contributing to dimension (volume) and stability (precision) in areas sensitive to temperature changes. Additionally, graphite has a higher thermal conductivity than most metals except gold, silver, copper, and aluminum, so it has a wide range of uses.

Additionally, graphite is an anisotropic material and is an excellent electrical and thermal conductor inside the stack due to in-plane metal bonding, but is a weak electrical and thermal conductor toward the layers due to weak van der Waals forces between layers. It is a material that is expected to have a wide range of applications as it has both metallic and non-metallic properties. Because graphite has excellent conductor properties, it is suitable for use as electrodes or brushes. Additionally, graphite's high boiling point makes it a suitable material for casting and molding. Because the carbon layers of graphite can be inserted into the layers, it has been traditionally used as a lubricant or pencil material. However, despite these advantages and wide applications of graphite, supply shortage is a major problem. Graphite has been experiencing supply problems due to widespread demand and limited reserves, so the need for artificial graphite is emerging as a good alternative to bridge the gap between supply and demand.

Comparison of artificial graphite and natural graphite

Graphite includes natural graphite, which is produced and mined in nature, and artificial, synthetic, pyrolytic graphite, which is manufactured by heat-treating coal-based and petroleum-based pitch at over 2500°C.

Artificial graphite is a composite produced by heat-treating petroleum or coal by-products at over 2,500°C to graphitize them, and has higher purity than natural graphite. In particular, it is excellent in light weight, heat resistance, electrical and thermal conductivity, chemical stability, and high strength, and is used as electrodes in the steel field, cathode materials for mobile phones, core materials for semiconductors and solar cells, moderators for nuclear power, and pencil lead for writing. .

Natural graphite has a higher degree of graphitization and is cheaper than artificial graphite, and has a high lithium ion storage capacity, especially when used as a lithium ion electrode material. However, the particle shape shows a needle-like or plate-like structure, and the surface area is large due to the irregular structure and the edge surface is exposed, so when applied to a battery, the edge surface is peeled or destroyed due to electrolyte penetration or decomposition reaction, causing a large irreversible reaction. In addition, plate-shaped particles are prone to being oriented in a stretched form on the current collector, so they have poor wettability with the electrolyte solution and low electrode density.

On the other hand, artificial graphite has a more stable crystal structure than natural graphite because it creates the crystal structure of graphite by applying high heat of over 2500℃, so the change in crystal structure is small even after repeated charging and discharging of lithium ions, so its lifespan is relatively long.

Problems in manufacturing artificial graphite

Representative artificial graphite materials, including electrodes for electric steelmaking, are manufactured by adding a binder such as pitch to a filler such as coke, forming it into a certain shape, and then baking and graphitizing it. After graphitization, high purity treatment is performed depending on the application, including semiconductor use. As a result, the impurity content in the graphite material decreases from hundreds to thousands of ppm to several ppm or less. High purification treatment is generally carried out by flowing a halogen gas such as freon or chlorine under heating at a high temperature of 2,000°C or higher to convert metal impurities into halides and evaporate them out of the graphite material. In addition, there are cases where high purity is performed simultaneously with graphitization, but the purity is slightly lower.

In particular, in order to produce highly crystalline artificial graphite, catalysts such as AlCl ₃ and BF ₃ must be used. In the case of AlCl ₃ , Al remains as an impurity during the artificial graphite manufacturing process, so an acid treatment process and a high purification process are required to remove it. Additionally, there is a risk that halogen elements may be released and corrode experimental equipment.

Characteristics of non-graphitizing carbon

Non-graphitic carbon has a disordered structure because the size of the hexagonal network planes composed of carbon atoms is small, and lamination growth is not well developed, and microcrystallites composed of hexagonal network planes are entangled with each other, or these microcrystals are mixed with the amorphous phase. It represents the structure that exists.

Non-graphitic carbon can be classified into soft carbon and hard carbon depending on the degree of ease of graphitization. These structural differences are due to differences in crystallite rearrangement behavior that occurs during the carbonization process of the carbon precursor.

Non-graphitizable carbon is made from charcoal, biomass, coke, etc., and because stacking of the graphite layer plane is greatly suppressed during the carbonization process, the crystallites are entangled with each other and arranged in a disorderly manner. That is, even after heat treatment, it has an amorphous structure in which relatively small hexagonal carbon layers are stacked randomly or non-uniformly. Therefore, the size of the crystallites is very small, and they are not arranged in a graphite structure even when heat treated at a high temperature of 2500°C or higher. This crystallographic amorphism results in wide angle X-ray scattering (WAXS) and neutron scattering (WANS). Meanwhile, in the case of easily graphitizable carbon, graphene layers are relatively arranged parallel to each other, making graphitization easy at high temperatures.

Hereinafter, each aspect of the present application will be described in detail.

The first aspect of the present application is,

A method for producing artificial graphite, comprising: a first step of mixing non-graphitizable carbon and a silicon precursor; A second step of heat treating the mixture formed in the first step to form silicon carbide; A third step of heat treating the formed silicon carbide in an air atmosphere to remove unreacted non-graphitized carbon; and a fourth step of producing highly crystalline artificial graphite by graphitizing the heat-treated silicon carbide.

Hereinafter, the method for manufacturing the highly crystalline artificial graphite according to the first aspect of the present application will be described in detail.

First, in one embodiment of the present application, the method for producing highly crystalline artificial graphite includes a first step of mixing non-graphitizable carbon and a silicon precursor.

In one embodiment of the present application, the non-graphitizable carbon is preferably a carbon material that has low crystallinity and contains many defects even after graphitization treatment, easily graphitized carbon that has high crystallinity at the graphitization temperature, and carbon material waste. Specifically, it may be characterized by using carbon black, activated carbon, isotropic carbon fiber, and mixtures thereof, more preferably carbon black.

In one embodiment of the present application, the silicon precursor is a material capable of supplying silicon, preferably using silicon, silicone oil, silica, and mixtures thereof, more preferably silicon.

In one embodiment of the present application, the mixing ratio of the non-graphitizable carbon and the silicon precursor is 1:0.1 to 1:1.5, preferably 1:0.3 to 1:1.2, more preferably 1:0.5 to 1:1.1. It may be a molar ratio of If the ratio is outside the range of 1:0.1 to 1:1.5, the content of the silicon precursor may be insufficient and too little silicon carbide may be generated, which may reduce the yield of artificial graphite, or if the content of the silicon precursor is too high, it may itself be an impurity. It can act as.

If the mixing ratio of the non-graphitizable carbon and silicon precursor is outside the above range, the crystallinity of the manufactured artificial graphite may decrease and contain many defects, or the proportion of wasted silicon may increase.

The mixing method can be performed by adding non-graphitizable carbon and silicon precursor to the solvent and then ultrasonic treatment.

Next, in one embodiment of the present application, a second step of forming silicon carbide by heat treating the mixture formed in the first step is included.

In one embodiment of the present application, the heat treatment in the second step is performed at a temperature of 1200 ℃ to 2100 ℃ for 30 minutes to 180 minutes, preferably at a temperature of 1250 ℃ to 2050 ℃ for 45 minutes to 120 minutes, more preferably Specifically, it may be characterized in that it is performed in an inert gas atmosphere at a temperature of 1300°C to 2000°C for 60 to 90 minutes.

If the heat treatment temperature in the above step is less than 1200°C or the reaction time is less than 30 minutes, the energy required for the reaction of the non-graphitizable carbon and the silicon precursor is not sufficient, so the formation of silicon carbide does not occur. On the other hand, if the reaction temperature exceeds 2100°C or exceeds 180 minutes, unnecessary energy is consumed and energy efficiency decreases.

Next, in one embodiment of the present application, a third step of removing unreacted non-graphitized carbon by heat treating the formed silicon carbide in an air atmosphere is included.

In one embodiment of the present application, the heat treatment in the third step is more preferably at a temperature of 300°C to 800°C for 60 minutes to 300 minutes, preferably at a temperature of 400°C to 700°C for 90 minutes to 270 minutes. Specifically, it may be characterized as being performed in an oxygen-containing atmosphere at 500°C to 600°C for 120 to 240 minutes.

If the heat treatment temperature in the above step is less than 300°C or the time is less than 60 minutes, there is a risk that the purity of the produced artificial graphite may decrease because the remaining non-graphitizable carbon cannot be sufficiently removed. Additionally, if the heat treatment temperature exceeds 800°C or exceeds 300 minutes, there is no significant effect and energy is wasted.

Next, in one embodiment of the present application, a fourth step of manufacturing highly crystalline artificial graphite by graphitizing the heat-treated silicon carbide is included.

In one embodiment of the present application, the fourth step of graphitization is performed by heating the heat-treated silicon carbide at a temperature of 2400°C to 3000°C for 30 minutes to 180 minutes, preferably at a temperature of 2500°C to 2900°C for 45 minutes. It may be characterized by heat treatment in an inert gas atmosphere for from 120 minutes, more preferably at 2600°C to 2800°C for 60 minutes to 90 minutes.

If the graphitization temperature in the above step is less than 2400°C or the reaction time is less than 30 minutes, the conversion rate of silicon carbide is low and contains a large amount of unreacted silicon carbide, resulting in low crystallinity of the produced artificial graphite. On the other hand, if the graphitization temperature exceeds 3000°C or exceeds 180 minutes, it does not significantly affect the crystallinity of the formed artificial graphite, consumes unnecessary energy, and reduces the lifespan of the graphitization processing device.

In one embodiment of the present application, the method for producing highly crystalline artificial graphite may be characterized by not using a halogen compound.

In one embodiment of the present application, the interlayer distance of the highly crystalline artificial graphite may be 0.34 nm, preferably 0.3380 nm, and more preferably 0.3372 nm or less.

In one embodiment of the present application, the peak intensity ratio (I d /I _g ) of the peak for defects (I _d ) and the crystallinity peak ( _{I g} ) measured by Raman spectrum measurement of the highly crystalline artificial graphite is 0.1 or less, It may preferably be 0.08 or less, and more preferably 0.05 or less. Specifically, the peak I _d for the defect (amorphous) has a peak in the vicinity of 1300 to 1400 cm ^-1 , preferably around 1350 cm ^-1 , and the crystalline peak Ig has a peak in the vicinity of 1550 to 1650 cm ^-1 , preferably may have a peak at a location around 1580 cm ^-1 . When the peak intensity ratio (I _d /I _g ) satisfies the above-mentioned range, the artificial graphite manufactured by one embodiment of the present invention can exhibit the effect of having high crystallinity and low defects.

The second aspect of the present application is,

A highly crystalline artificial graphite made of a mixture of non-graphitizable carbon and a silicon precursor, wherein the non-graphitizable carbon is selected from the group consisting of carbon black, activated carbon, isotropic carbon fiber, and mixtures thereof, and the silicon precursor is silicon, silicon Provided is highly crystalline artificial graphite selected from the group consisting of oil, silica, and mixtures thereof.

Detailed description of parts overlapping with the first aspect of the present application has been omitted, but the content described in the first aspect of the present application can be applied equally even if the description is omitted in the second aspect.

Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement it. However, the present invention may be implemented in many different forms and is not limited to the embodiments described herein.

Example 1: Preparation of highly crystalline artificial graphite

Step 1: Mixing of non-graphitizable carbon and silicon precursors

To produce highly crystalline artificial graphite, carbon black, a representative non-graphitizable carbon, was used, and pure silicon was selected as the silicon precursor. 0.5 mol of carbon black and silicon were added to isopropanol at a molar ratio of 1:1, and then sonicated for 1 hour to mix the carbon black and silicon. After mixing, the carbon black/silicon mixture was prepared by drying at 90°C for 12 hours to remove isopropanol.

Second Step: Formation of Silicon Carbide

To produce artificial graphite from a carbon black/silicon mixture, the mixture was placed in a graphitization reactor and the temperature was raised to 1500°C. After raising the temperature, it was maintained at the same temperature for 1 hour to form silicon carbide.

Third step: Removal of unreacted non-graphitized carbon

To remove unreacted carbon black contained in the silicon carbide, heat treatment was performed at 600°C for 180 minutes in an air atmosphere.

Step 4: Graphitization of Silicon Carbide

The silicon carbide was heated to 2700°C, maintained for 1 hour, and then naturally cooled to room temperature to produce highly crystalline artificial graphite.

Example 2: Preparation of highly crystalline artificial graphite

Graphene was manufactured in the same manner as in Example 1, except that the molar ratio of carbon black and silicon was used at 1:0.5.

Example 3: Preparation of highly crystalline artificial graphite

Graphene was prepared in the same manner as in Example 1, except that the molar ratio of carbon black and silicon was 1:0.3.

Example 4: Preparation of highly crystalline artificial graphite

Graphene was manufactured in the same manner as in Example 1, except that the molar ratio of carbon black and silicon was used as 1:0.1.

Comparative Example 1: Production of artificial graphite without silicon precursor

In Comparative Example 1, graphene was manufactured in the same manner as Example 1, except that silicon was not used.

Experimental Example 1: Evaluation of physical properties of graphene

1. Crystallinity analysis of manufactured graphene

The crystal structures of silicon carbide and graphene prepared from the above examples and comparative examples were evaluated using X-ray diffraction (XRD). The XRD analysis results of the Examples and Comparative Examples prepared from the second step are shown in Figure 2, the XRD analysis results of the Examples and Comparative Examples prepared from the third step are shown in Figure 3, and the Examples prepared from the fourth step and the XRD analysis results of the comparative example are shown in Figure 4.

As a result of the XRD analysis of the silicon carbide that went through the second step in Figure 2, it was confirmed that the peak of the silicon carbide was sharp and high, and that the silicon peak did not appear. Additionally, in the case of Examples 2 and 3, it was confirmed that some noise occurred around 22° to 28°.

On the other hand, as a result of XRD analysis of silicon carbide that underwent the third step in Figure 3, it was confirmed that the noise that appeared around 22° to 28° disappeared. Looking at the position of the peak and the difference between Figures 2 and 3, it is believed that the noise appearing around 22° to 28° is caused by unreacted carbon black. In other words, it is judged that all unreacted carbon black was removed during the third step and the noise that appeared around 22° to 28° disappeared.

From the results of Figures 2 and 3, it was confirmed that the XRD results were the same in Example 1 even without the third step. Carbon and silicon react in a 1:1 ratio to produce silicon carbide. Therefore, it is judged that most of the carbon black and the silicon precursor reacted and no noise appeared around 22° to 28° in Example 1 in FIG. 3.

In the XRD analysis results of Figure 4, it was confirmed that Examples 1, 2, 3, and 4 all showed sharp and high peaks around 26°. On the other hand, in Comparative Example 1, a blunt and low peak appeared. These sharp and high peaks indicate that the artificial graphite produced by the reaction of the added silicon precursor and carbon black has high crystallinity.

In order to confirm the crystallinity of the artificial graphite produced from the XRD analysis results in FIG. 4, the distance (d002) between the graphene layers making up the graphite was calculated and is shown in Table 2. Example 1 was very close to the theoretical distance between graphene layers, 0.3354 nm, and Examples 2, 3, and 4 also had similar values. However, in the case of Comparative Example 1, it was confirmed that the interlayer distance was 0.34334 nm, which was wider than that of the Example.

From the XRD analysis results, it was confirmed that non-graphitizable carbon does not have a graphite structure even at a high temperature of 2700°C or higher (Comparative Example 1), while the artificial graphite produced through the present invention has a high crystallinity close to the theoretical graphite structure. .

2. Defect analysis of manufactured artificial graphite

Defects of the artificial graphite prepared from the above examples and comparative examples were evaluated using Raman analysis, and this is shown in FIG. 5. The D band, meaning defects, appeared around 1350 cm ^-1 of Raman shift, and the G band, meaning crystallinity, appeared around 1580 cm ^-1 .

In the case of Example 1, Example 2, Example 3, and Example 4, the G band peak appeared high and the D band peak was absent or weak, whereas in Comparative Example 1, the D band peak appeared high. .

Additionally, the peak values and peak intensity ratio Id/Ig of the D band and G band are shown in Table 2. As the value of Id/Ig decreases, it means that the manufactured artificial graphite has fewer defects. As a result of XRD and Raman analysis, the manufactured artificial graphite is judged to be high-quality artificial graphite with excellent crystallinity and no defects.

3. Shape evaluation of manufactured artificial graphite

Artificial graphite and untreated carbon black prepared from the above examples and comparative examples were analyzed using SEM, and this is shown in FIG. 6. In the case of Comparative Example 1, the carbon black shape was maintained as is, while in the case of Examples 1, 2, 3, and 4, it was confirmed that it changed into an angled block shape.

In order to more accurately confirm the surface shape of the artificial graphite prepared from the above examples and comparative examples, 0.1 mg of graphene was added to 1 mL of ethanol, ultrasonicated for 3 minutes, and analyzed using TEM, which is shown in Figure 7. It was. In the case of Comparative Example 1, it was hollow while maintaining the shape of carbon black, while Examples 1, 2, 3, and 4 were all exfoliated and were confirmed to contain a thin layer similar to graphene. .

4. Electrical conductivity of manufactured artificial graphite

The electrical conductivity of the artificial graphite prepared from the above examples and comparative examples was measured using IEC TS 62607-6-1 (Graphene-based material - Volume resistivity: four probe method), and is shown in FIG. 8.

IEC TS 62607-6-1 expresses the electrical conductivity according to the density of the measured sample. It was measured by applying pressure from normal pressure to 196.13 MPa (2000 kgf/cm ² ) using 0.1 g of the sample made through Examples and Comparative Examples. did. In Comparative Example 1, the density of the sample was low, so even when a pressure of 196.13 MPa was applied, a low density of 0.7 g/cm ³ was observed. At the same density (0.7g/cm ³ ), Example 1 showed a high electrical conductivity of 160.5 S/cm, and Example 2, Example 3, and Example 4 showed electrical conductivity of 145.1, 143.2, and 141.8 S/cm, respectively. showed. On the other hand, Comparative Example 1 showed a low conductivity of 21.7 S/cm.

From the results of FIGS. 1 and 4, it is judged that the crystallinity of Example 1, Example 2, Example 3, and Example 4 was high and defects were reduced, indicating that this result was obtained. In addition, Example 1 showed a high electrical conductivity of 540.8 S/cm at a density of 2.0 g/cm ³ , and Example 2, Example 3, and Example 4 showed conductivity of 502.4, 493.0, and 487.9 S/cm, respectively. It seemed.

Claims (13)

In the manufacturing method of artificial graphite,
A first step of adding non-graphitizable carbon and silicon precursor to a solvent and then mixing them using ultrasonic treatment;
A second step of heat treating the mixture formed in the first step to form silicon carbide;
A third step of heat treating the formed silicon carbide in an air atmosphere to remove unreacted non-graphitized carbon; and
A fourth step of graphitizing the heat-treated silicon carbide to produce highly crystalline artificial graphite,
The mixing ratio of the non-graphitizable carbon and silicon precursor is a molar ratio of 1:0.3 to 1:1.2,
The interlayer distance of the highly crystalline artificial graphite is 0.3380 nm or less,
Highly crystalline artificial graphite, characterized in that the peak intensity ratio (I _d /I _g ) of the peak for defects (I _d ) and the crystalline peak (I _g ) as measured by the Raman spectrum of the highly crystalline artificial graphite is 0.05 or less. Manufacturing method.
According to paragraph 1,
A method for producing highly crystalline artificial graphite, characterized in that the non-graphitizable carbon is selected from the group consisting of carbon black, activated carbon, isotropic carbon fiber, and mixtures thereof.
According to paragraph 1,
A method for producing highly crystalline artificial graphite, wherein the silicon precursor is selected from the group consisting of silicon, silicone oil, silica, and mixtures thereof.
delete According to paragraph 1,
A method for producing highly crystalline artificial graphite, characterized in that the heat treatment in the second step is performed in an inert gas atmosphere at a temperature of 1200 ° C. to 2100 ° C. for 30 minutes to 180 minutes.
According to paragraph 1,
A method of producing highly crystalline artificial graphite, characterized in that the third step heat treatment is performed in an oxygen-containing atmosphere at a temperature of 300 ℃ to 800 ℃ for 60 to 300 minutes.
According to paragraph 1,
The fourth step of graphitization is a method of producing highly crystalline artificial graphite, characterized in that the heat-treated silicon carbide is heat-treated in an inert gas atmosphere at a temperature of 2400 ℃ to 3000 ℃ for 30 to 180 minutes.
According to paragraph 1,
A method for producing highly crystalline artificial graphite, characterized in that the method for producing highly crystalline artificial graphite does not use a halogen compound.
delete delete Highly crystalline artificial graphite manufactured according to the manufacturing method of claim 1,
The non-graphitizable carbon is selected from the group consisting of carbon black, activated carbon, isotropic carbon fiber, and mixtures thereof,
The silicone precursor is selected from the group consisting of silicone, silicone oil, silica, and mixtures thereof,
The interlayer distance of the highly crystalline artificial graphite is 0.3380 nm or less,
Highly crystalline artificial graphite, wherein the peak intensity ratio (I _d /I _g ) of the peak for defects (I _d ) and the crystalline peak (I _g ) as measured by the Raman spectrum of the highly crystalline artificial graphite is 0.05 or less. delete delete