Method of manufacturing doped graphite flake

Abstract

The present invention provides a method for manufacturing doped graphite flakes. According to one embodiment of the present invention, graphite flakes can be manufactured economically by supplying a doping source together with an inert gas during the manufacturing process via air jet milling. Doped graphite flakes manufactured by the method according to one embodiment of the present invention can be applied in various fields such as petrochemicals, cosmetics, pharmaceuticals, and batteries.

Description

Technology Field

[0001] The present invention relates to a method for manufacturing doped graphite flakes. Specifically, it relates to a method for manufacturing doped graphite flakes simply and effectively. Background Technology

[0002] Graphite is a chemically very stable material consisting of layers formed by the connection of rings made of six carbon atoms, with strong heat resistance, thermal shock resistance, and corrosion resistance, as well as good electrical and thermal conductivity.

[0003] In particular, graphite flakes are used as raw materials for various electrode materials in secondary batteries and electrolysis devices, as well as for heat-resistant devices.

[0004] Graphite flakes can be manufactured by grinding graphite raw materials using mechanical or chemical methods. One mechanical method is air jet milling, which grinds the sample using high-pressure compressed air in an air jet mill device. Specifically, graphite raw materials fed into the air jet mill from the hopper are moved to the center of the mill by high-pressure air sprayed from the compressor nozzle and are ground by mutual collision. The powder ground in this manner within the air jet mill is automatically classified to the desired particle size by a classifier installed at the top of the mill and transferred to the collection section.

[0005] Meanwhile, when grinding graphite using air jet milling, the process can be carried out in a high-pressure atmosphere of inert gases such as helium (He), argon (Ar), or nitrogen (N2), or in a halogen gas atmosphere. This is because graphite may oxidize if milled in an air atmosphere.

[0006] On the other hand, conventional mechanical grinding aims simply to grind the graphite raw material, so it is necessary to improve the electrical properties of the graphite flakes through additional processes. For example, after manufacturing the graphite flakes, a separate doping process must be added using chemical vapor deposition with amine compounds, hydrothermal synthesis, other chemical reactions, or plasma treatment, which presents economic and time disadvantages in terms of mass production. Prior art literature

[0007] Korean Registered Patent No. 10-2530783 The problem to be solved

[0008] The technical problem that the present invention aims to solve is to provide a method for economically manufacturing doped graphite flakes by simultaneously performing grinding and doping of graphite raw materials. means of solving the problem

[0009] According to one aspect of the present invention, the step of preparing a graphite raw material; and

[0010] The above graphite raw material includes the step of grinding it with an air jet mill,

[0011] A method for manufacturing doped graphite flakes is provided, wherein the grinding step is performed while supplying a mixed gas of air and a dopant source gas.

[0012] According to another aspect of the present invention, doped graphite flakes are provided that are manufactured by the above method and have a dopant content of 0.01 vol% to 30 vol%. Effects of the invention

[0013] According to a manufacturing method according to one embodiment of the present invention, doped graphite flakes can be produced in large quantities through a simple process. Brief explanation of the drawing

[0014] FIG. 1a is a partial schematic diagram of an air jet mill device usable in a manufacturing method according to one embodiment of the present invention. FIG. 1b is a schematic diagram of the grinding section of an air jet mill device usable in a manufacturing method according to one embodiment of the present invention. FIG. 1c is a schematic cross-sectional view of the grinding section of an air jet mill device usable in a manufacturing method according to one embodiment of the present invention. FIG. 2 is a photograph of an air jet mill used in a manufacturing method according to one embodiment of the present invention. Figure 3 is an SEM photograph and graph showing the particle size and size distribution of graphite flakes produced by the manufacturing method according to Reference Example 1 of the present invention. Figure 4 is a Raman spectrum of graphite flakes prepared by the method according to Reference Example 1 of the present invention. FIGS. 5a to 5h are FT-IR spectra of doped graphite flakes prepared by the manufacturing method according to Examples 1 to 6 and Comparative Example 1 of the present invention. Specific details for implementing the invention

[0015] In this specification, when a part is described as "comprising" a certain component, this means that, unless specifically stated otherwise, it does not exclude other components but may include additional components.

[0016] The present invention will be described in more detail below with reference to the drawings.

[0017] A method for manufacturing doped graphite flakes according to one aspect of the present invention comprises the steps of: preparing a graphite raw material; and grinding the graphite raw material using an air jet mill, wherein the grinding step is performed while supplying a mixed gas of an inert gas and a dopant source gas.

[0018] According to one embodiment of the present invention, graphite raw material can be crushed and graphite doped at the same time, so that doped graphite flakes with excellent electrical properties can be obtained in a single process.

[0019] In other words, since the grinding and doping of the graphite raw material are performed simultaneously, doped graphite flakes can be manufactured economically.

[0020] In the manufacturing method according to one embodiment of the present invention, air jet mill devices that can be used may be used without limitation, such as nozzle suction type (vertical or horizontal), nozzle internal suction type, collision wall type, jet airflow collision type, fluid bed type, and composite type.

[0021] FIG. 1 is a schematic diagram of an air jet mill device used in a manufacturing method according to one embodiment of the present invention. FIG. 1a is a partial schematic diagram of an air jet mill device usable in a manufacturing method according to one embodiment of the present invention, FIG. 1b is a schematic diagram of a grinding section of an air jet mill device usable in a manufacturing method according to one embodiment of the present invention, and FIG. 1c is a schematic cross-sectional view of a grinding section of an air jet mill device usable in a manufacturing method according to one embodiment of the present invention.

[0022] The air jet mill device consists of a jet mill that performs a grinding action and a compressor that supplies high-pressure air to the jet mill. It is a device that uses high-pressure compressed air to form a supersonic jet stream inside the grinding chamber, thereby grinding particles through collision, friction, and shear force.

[0023] The grinding power source of such air jet mill devices is a jet stream. High-pressure compressed air is required to generate this jet stream, and for this purpose, an air compressor is necessary.

[0024] A non-cooled air jet mill device (1) usable in a manufacturing method according to one embodiment of the present invention comprises, as shown in FIGS. 1a and 1c, a raw material supply unit (10) for supplying graphite raw material, a crushing unit (20) of an air jet mill that crushes and classifies the raw material supplied from the raw material supply unit (10) by a jet stream of compressed gas supplied through a gas inlet (40, 40', 40''), and a collecting unit (30, 30') that collects the crushed and classified raw material according to size.

[0025] First, the graphite raw material is supplied to the grinding unit (20) through the raw material supply unit (10). At the same time, a mixed gas of inert gas and doping source gas is supplied into the grinding unit (20) through the gas inlet (40, 40', 40'').

[0026] As illustrated in FIG. 1b, a vortex is generated by a mixture of inert gas and a doping source gas injected into the grinding section (20), through which collisions and friction occur between the graphite raw materials, causing the graphite raw materials to be ground. The ground graphite raw materials that reach the inner wall of the grinding section are further ground by shear force. During this grinding process, doping of the ground graphite occurs by the doping source gas. The graphite flakes, having been ground and doped in this manner, are discharged out of the grinding section (20) through the discharge port and collected in the collection section (30, 30'). The collected doped graphite flakes can be ground again as needed.

[0027] According to one embodiment of the present invention, the dopant source gas is ammonia (NH3), hydrazine (NH2NH2), pyridine (C5H5N), acetonitrile (CH3CN), triethanolamine (C6H 15 It may be one or more sources selected from NO3) and aniline (C6H7N), but is not limited thereto.

[0028] According to one embodiment of the present invention, the inert gas may be nitrogen or argon.

[0029] According to one embodiment of the present invention, the mixed volume ratio of the inert gas and the dopant source gas among the mixed gases is 1:0.001 to 1:1000, for example, 1:0.001 to 1:100, 1:0.001 to 1:50, 1:001 to 1:30, 1:0.01 to 1:20, 1:0.001 to 1:10, 1:0.01 to 1:100, 1:0.01 to 1:100, 1:0.01 to 1:50, 1:0.01 to 1:30, 1:0.01 to 1:20, 1:0.01 to 1:10, 1:0.1 to 1:100, 1:0.1 to 1:100, 1:0.1 to It may be 1:50, 1:0.1 to 1:30, 1:0.1 to 1:20, 1:0.1 to 1:10, 1:1 to 1:100, 1:1 to 1:100, 1:1 to 1:50, 1:1 to 1:30, 1:1 to 1:20, or 1:1 to 1:10. When it falls within the above range, the grinding of the graphite raw material occurs well, and the doping of the dopant can be effectively achieved.

[0030] According to one embodiment of the present invention, the supply rate of the mixed gas may be 0.1 to 1,000 SCCM (Standard Cubic Centimeter per Minute), for example, 0.1 to 500 SCCM, 0.1 to 300 SCCM, 0.1 to 200 SCCM, 0.1 to 180 SCCM, 0.1 to 150 SCCM, 0.1 to 130 SCCM, 0.1 to 120 SCCM, 0.1 to 110 SCCM, or 1 to 100 SCCM. When the mixed gas is supplied at a supply rate within the above range, doped graphite flakes of a desired size can be obtained, and doping can be effectively achieved.

[0031] An air jet mill device usable in a manufacturing method according to one embodiment of the present invention may exclude equipment for discharging heat (such as a chiller) because it can exhibit a cooling effect when a high-pressure mixed gas undergoes volume expansion after passing through a nozzle. Since the air jet mill device usable in a manufacturing method according to one embodiment of the present invention uses toxic gases such as ammonia as a dopant source gas, it may additionally include a scrubber capable of purifying such gases.

[0032] In addition, if a device equipped with classification capabilities, such as a cyclone or an air-flow classifier, is installed in a closed circuit of the air jet mill device used to classify and remove flakes with relatively large particle sizes, flakes of uniform particle size can be efficiently obtained, and the maximum particle size or average particle size can be kept small.

[0033] Doped graphite flakes according to another aspect of the present invention are prepared by the above method and have a dopant content of 0.01 vol% to 30 vol%. By having a dopant content within the above range, excellent electrical properties may be achieved. The dopant content in the doped graphite flakes can be measured by known methods, for example, by energy dispersive X-ray spectroscopy (EDS or EDX), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, or Fourier transform infrared spectroscopy (FT-IR).

[0034] According to one embodiment of the present invention, the dopant is -NH2, -NHNH2, -C5H4N, -CH2CN,

[0035] -C6H 14 It may be one or more dopants selected from NO3 and -C6H6N. As it is doped with the above dopant, the electrical properties of the graphite flakes may be improved.

[0036] According to one embodiment of the present invention, the doped graphite flakes have an average particle size of 0.01 to 100 μm and 0.05 to 50 μm. , 0.1 to 10 μm, or It may be 1 to 5 μm. By having an average particle size within the above range, it can be effectively used in electrical devices such as desired electrode materials.

[0037] The doped graphite powder according to one embodiment of the present invention can be applied in various fields such as petrochemicals, cosmetics, pharmaceuticals, and batteries.

[0039] The present invention will be explained in more detail through the following examples, but the scope of the present invention is not limited thereto.

[0040] Examples

[0041] FIG. 2 is a photograph of an air jet mill device used in the following example. The grinding conditions of the air jet mill device in FIG. 2 are as follows.

[0042] Grinding air pressure: 4.0~5.0 bar

[0043] Raw material input air pressure: 5.0~6.5 bar

[0044] Raw material feeding screw speed: 8~10 rpm

[0046] Reference Example 1

[0047] 2000 g of graphite purchased from Seongha Co., Ltd. was prepared as the raw material. The grinding conditions were set before operating the air jet mill. Preparations were made to supply an inert gas (nitrogen), the prepared graphite raw material was placed into the inlet of the air jet mill, and the air jet mill was operated to grind the graphite raw material for 4 hours. During the grinding process, the inert gas was supplied, and the ground graphite flakes were recovered from the outlet of the air jet mill. The graphite flakes obtained by the above method were ground three more times under the same conditions, and the ground graphite flakes were collected.

[0049] Preparation of doped graphite flakes

[0050] Example 1

[0051] Doped graphite flakes were prepared by supplying a mixture of an inert gas and a dopant source gas. Graphite was ground in the same manner as in Reference Example 1, except that the grinding conditions of the air jet mill regarding the mixed gas containing the dopant source gas were changed as follows. Ammonia was selected as the dopant source gas in Example 1.

[0052] Mixture volume ratio of inert gas and dopant source gas: 1:10

[0053] Mixed gas supply rate: 10 SCCM (Standard Cubic Centimeter per Minute)

[0054] Mixed gas pressure: 1.0 MPa

[0056] Examples 2 to 6 and Comparative Example 1

[0057] Doped graphite flakes were prepared in the same manner as in Example 1, except that the air jet mill grinding conditions were changed as shown in Table 1 below.

[0059] Mixed gas volume ratio (inert gas:dopant source gas) Mixed gas supply rate (SCCM) Example 2 1:0.1 10 Example 3 1:1 10 Example 4 1:10 10 Example 5 1:10 0.1 Example 6 1:1 100 Comparative Example 1 1:0 0.1

[0061] Measurement of graphite flake particle size and size distribution

[0062] Figure 3 is an SEM photograph and graph showing the particle size and size distribution of the graphite flakes of Reference Example 1.

[0063] As shown in FIG. 3, it can be seen that the graphite flakes of Reference Example 1 have an average particle size of 1 μm to 15 μm. In addition, it can be seen that as the number of grinding cycles increases, the size of the graphite flakes decreases, and the particle size distribution narrows, resulting in higher uniformity of the flake size.

[0064] Based on this, the doped graphite flakes of Examples 1 to 6 also have an average particle size of 1 μm to 15 μm, similar to the graphite flakes of Reference Example 1, and it can be expected that as the number of grinding cycles increases, the size of the doped graphite flakes decreases and the uniformity increases.

[0066] Quality measurement of graphite flakes

[0067] Figure 4 is the Raman spectrum of the graphite flakes of Reference Example 1. (Sample No. 1: graphite raw material, Sample No. 3: ground once, Sample No. 5: ground twice, Sample No. 7: ground three times). For reference, the Raman spectrum of graphene oxide is also shown.

[0068] As shown in Figure 4, the D peak of the graphite flakes indicates that there is minimal damage even after grinding using an air jet mill.

[0070] Measurement of doping in graphite flakes

[0071] Meanwhile, in order to determine whether the manufactured graphite flakes were doped, FT-IR (Fourier transform infrared spectroscopy) analysis was performed on the graphite flakes of Examples 1 to 6 and the Comparative Example.

[0072] Figure 5a is the FT-IR spectrum of the doped graphite flakes prepared in Example 1.

[0073] As shown in Fig. 5a, it can be seen that the doped graphite flakes of Example 1 are effectively doped with -NH2.

[0074] Figures 5b, 5c, 5d, and 5e are the FT-IR spectra of Comparative Example 1, Example 2, Example 3, and Example 4, respectively. Through this, it can be confirmed that as the proportion of the dopant source gas in the mixed gas increases, the CN peak becomes more distinct, indicating that -NH2 is more heavily doped.

[0075] Figures 5f, 5g, and 5h are the FT-IR spectra of Examples 5, 3, and 6, respectively. Through this, it can be confirmed that as the proportion of the dopant source gas in the mixed gas increases, the CN peak becomes more distinct, indicating that more -NH2 is doped.

[0077] As described above, according to one embodiment of the present invention, graphite flakes are generated and simultaneously doped with a dopant to induce excellent chemical activity, thereby increasing the scalability of graphite flakes to various fields compared to existing ones.

[0079] The present invention is not limited by the embodiments described above and the attached drawings, but is intended to be limited by the appended claims. Accordingly, various substitutions, modifications, and changes may be made by those skilled in the art within the scope of the technical concept of the present invention as described in the claims, and such are also to be considered to fall within the scope of the present invention. Explanation of the symbols

[0080] 1: Air jet mill device 10: Supply unit 20: Grinding section 30, 30': Collection section 40, 40', 40'': Gas inlet

Claims

Claim 1 A method for manufacturing doped graphite flakes, comprising the steps of: preparing a graphite raw material; and grinding the graphite raw material with an air jet mill, wherein the grinding step is performed while supplying a mixed gas of an inert gas and a dopant source gas, and the volume ratio of the inert gas and the dopant source gas in the mixed gas is 1:0.001 to 1:1000. Claim 2 In claim 1, the dopant source gas is ammonia (NH3), hydrazine (NH2NH2), pyridine (C5H5N), acetonitrile (CH3CN), triethanolamine (C6H 15 A method for preparing doped graphite flakes, wherein one or more selected from NO3) and aniline (C6H7N). Claim 3 delete Claim 4 A method for manufacturing doped graphite flakes according to claim 1, wherein the supply rate of the mixed gas is 0.1 to 1,000 SCCM (Standard Cubic Centimeter per Minute). Claim 5 Doped graphite flakes manufactured by a method according to any one of claims 1, 2 and 4, wherein the dopant content is 0.01 vol% to 30 vol%. Claim 6 In claim 5, doped graphite flakes having an average particle size of 0.01 to 100 μm. Claim 7 In paragraph 5, the above dopant is -NH2, -NHNH2, -C5H4N, -CH2CN, -C6H 14 Doped graphite flakes that are one or more selected from NO3 and -C6H6N.

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