Carbide-derived carbon manufactured by using heat treatment at vacuum and method thereof

Abstract

Disclosed is a method of preparing a carbide-derived carbon having high ion mobility for use in a lithium battery anode material, a lithium air battery electrode, a supercapacitor electrode, and a flow capacitor electrode, including thermally treating a carbide compound in a vacuum, thus obtaining a vacuum-treated carbide compound; and thermochemically reacting the vacuum-treated carbide compound with a halogen element-containing gas, thus extracting the element other than carbon from the vacuum-treated carbide compound, wherein annealing can be further performed after thermochemical reaction. This carbide-derived carbon has a small pore distribution, dense graphite fringe, and a large lattice spacing and thus high ion mobility, compared to conventional carbide-derived carbon obtained only by thermochemical reaction with a halogen element-containing gas.

Claims

1. A method of preparing a carbide-derived carbon, comprising: thermally treating a carbide compound in a vacuum, thus obtaining a vacuum-treated carbide compound wherein lattice spacing of the vacuum-treated carbide compound is increased; and thermochemically reacting the vacuum-treated carbide compound with a halogen element-containing gas, thus extracting an element other than carbon from the vacuum-treated carbide compound, wherein the carbine-derived carbon has an XRD (X-ray diffraction) peak intensity of 6000 to 8000 between 20° and 30°; and; wherein thermally treating in a vacuum is performed at 1100˜1900° C. for 3˜7 hr.

2. The method of claim 1, wherein the carbide compound is a compound of carbon and an element selected from the group consisting of Groups 3, 4, 5, and 6 elements, and combinations thereof.

3. The method of claim 2, wherein the carbide compound is at least one selected from the group consisting of SiC, B.sub.xC.sub.y, TiC, ZrC.sub.x, Al.sub.xC.sub.y, Ca.sub.xC.sub.y, Ti.sub.xTa.sub.yC, Mo.sub.xW.sub.yC, TiN.sub.xC.sub.y, ZrN.sub.xC.sub.y, SiC.sub.4, TiAlC, and Mo.sub.2C (wherein x and y are stoichiometrically determined).

4. The method of claim 3, wherein the carbide compound is TiC.

5. The method of claim 1, wherein the halogen element-containing gas is selected from the group consisting of Cl.sub.2, TiCl.sub.4, and F.sub.2.

6. The method of claim 5, wherein the halogen element-containing gas is Cl.sub.2.

7. The method of claim 1, wherein thermochemically reacting is performed at 200˜1200° C.

8. The method of claim 7, wherein thermochemically reacting is performed for 3˜5 hr.

9. The method of claim 1, further comprising performing annealing with any one gas selected from the group consisting of H.sub.2, Ar, N.sub.2, and NH.sub.3, after thermochemically reacting.

10. The method of claim 9, wherein annealing is performed for 1˜3 hr.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The above and other objects, features and advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

(2) FIG. 1 illustrates a graph of the N.sub.2 adsorption curve of vacuum-treated TiC-CDC obtained by thermal treatment at 1500° C. in a vacuum and thermochemical reaction with Cl.sub.2 gas at 1200° C. and TiC-CDC obtained by thermochemical reaction with Cl.sub.2 gas at 1200° C.;

(3) FIG. 2 illustrates a graph of the pore size distribution measured by a Barrett-Joyner-Halenda (BJH) method in N.sub.2 adsorption curves of vacuum-treated TiC-CDC obtained by thermal treatment at 1500° C. in a vacuum and thermochemical reaction with Cl.sub.2 gas at 1200° C. and TiC-CDC obtained by thermochemical reaction with Cl.sub.2 gas at 1200° C.;

(4) FIG. 3 illustrates a graph of the pore size distribution measured by a micropore (MP) method in vacuum-treated TiC-CDC obtained by thermal treatment at 1500° C. in a vacuum and thermochemical reaction with Cl.sub.2 gas at 1200° C. and TiC-CDC obtained by thermochemical reaction with Cl.sub.2 gas at 1200° C.;

(5) FIG. 4 illustrates a graph of the XRD pattern of vacuum-treated TiC-CDC obtained by thermal treatment at 1500° C. in a vacuum and thermochemical reaction with Cl.sub.2 gas at 1200° C. and TiC-CDC obtained by thermochemical reaction with Cl.sub.2 gas at 1200° C.; and

(6) FIGS. 5A and 5C illustrate transmission electron microscope (TEM) images of TiC, FIGS. 5B and 5D illustrate TEM images of vacuum-treated TiC obtained by thermal treatment at 1500° C. in a vacuum, FIG. 5E illustrates a TEM image of TiC-CDC obtained by thermochemical reaction with Cl.sub.2 gas at 1200° C., and FIG. 5F illustrates a TEM image of vacuum-treated TiC-CDC obtained by thermal treatment at 1500° C. in a vacuum and thermochemical reaction with Cl.sub.2 gas at 1200° C.

DESCRIPTION OF SPECIFIC EMBODIMENTS

(7) The present invention addresses a method of preparing a carbide-derived carbon (CDC), comprising: thermally treating a carbide compound in a vacuum, thus obtaining a vacuum-treated carbide compound; and thermochemically reacting the vacuum-treated carbide compound with a halogen element-containing gas, thus extracting the element other than carbon from the vacuum-treated carbide compound.

(8) The carbide compound may be a compound of carbon and any element selected from the group consisting of Groups 3, 4, 5, and 6 elements, and combinations thereof. Particularly useful is any one selected from the group consisting of SiC, B.sub.xC.sub.y, TiC, ZrC.sub.x, Al.sub.xC.sub.y, Ca.sub.xC.sub.y, Ti.sub.xTa.sub.yC, Mo.sub.xW.sub.yC, TiN.sub.xC.sub.y, ZrN.sub.xC.sub.y, SiC.sub.4, TiAlC, and Mo.sub.2C, but the carbide compound is not limited thereto so long as it is a compound of carbon and any element selected from the group consisting of Groups 3, 4, 5, and 6 elements, and combinations thereof. As such, x and y may be stoichiometrically determined.

(9) Thermally treating the carbide compound in a vacuum is performed at 1100˜1900° C., preferably 1400˜1600° C., and more preferably 1500° C. Also, such thermal treatment in a vacuum is carried out for 3˜7 hr, and preferably for 4 hr. When the carbide compound is thermally treated in a vacuum in this way, micrometer-sized carbide particles of the carbide compound may be agglomerated into a high-density agglomerate.

(10) The halogen element-containing gas may be Cl.sub.2, TiCl.sub.4 or F.sub.2, but is not limited thereto so long as it is halogen element-containing gas.

(11) The thermochemical reaction between the vacuum-treated carbide compound and the halogen element-containing gas is carried out at 200˜1200° C., preferably 800˜1200° C. and more preferably 1200° C. The thermochemical reaction time with the halogen element-containing gas may be set to 3˜5 hr.

(12) When the vacuum-treated carbide compound is thermochemically reacted with the halogen element-containing gas, the element other than carbon is removed from the vacuum-treated carbide compound, thus forming nanopores, yielding a carbide-derived carbon having nano-sized pores and also dense graphite crystallinity.

(13) The method of preparing the carbide-derived carbon according to the present invention may further include annealing the vacuum-treated carbide compound with any one gas selected from the group consisting of H.sub.2, Ar, N.sub.2, and NH.sub.3, after thermochemically reacting the vacuum-treated carbide compound with the halogen element-containing gas. When annealing is performed in this way, any halogen gas or metal product remaining on the surface of carbon after thermochemical reaction may be removed, thus obtaining a carbide-derived carbon having high purity. Also, H.sub.2 gas used for annealing is merely illustrative and any known gas able to react with the halogen gas or metal product may be adopted therefor.

(14) In addition, the present invention addresses a carbide-derived carbon prepared by thermally treating a carbide compound in a vacuum to obtain a vacuum-treated carbide compound, which is then thermochemically reacted with a halogen element-containing gas, thus extracting the element other than carbon from the vacuum-treated carbide compound. Also, the present invention addresses a carbide-derived carbon prepared by thermally treating a carbide compound in a vacuum to obtain a vacuum-treated carbide compound, which is then thermochemically reacted with a halogen element-containing gas and then annealed with H.sub.2 gas, thus extracting the element other than carbon from the vacuum-treated carbide compound.

(15) The carbide-derived carbon subjected to annealing may exhibit high purity by removing the halogen gas or metal product from the surface of carbon after thermochemical reaction, compared to carbide-derived carbon not subjected to annealing. However, this does not mean that the purity of the carbide-derived carbon not subjected to annealing is low.

(16) The carbide-derived carbon may have a BET area of 1200˜1700 m.sup.2/g, and an XRD intensity of 6000˜8000 of a peak located between 20° and 30° based on the XRD analytical results.

(17) The carbide-derived carbon has nano-sized pores, dense graphite crystallinity, and a large lattice spacing of a basal plane to thus enable efficient ion movement, and thereby may be utilized as an energy storage medium in various fields. Examples of the energy storage medium may include, but are not limited to, anodes for primary batteries, secondary batteries and lithium batteries, lithium air battery electrode materials, supercapacitor electrodes, flow capacitor electrodes, fuel cell catalyst supports, and hydrogen storage mediums.

(18) With reference to the appended drawings, a better understanding of the present invention may be obtained via the following examples, which are set forth to illustrate, but are not to be construed as limiting the present invention. Examples of the present invention are provided for a full explanation to those skilled in the art.

Example 1: Preparation of Vacuum-Treated TiC-CDC Via Thermal Treatment at 1500° C. in Vacuum and Thermochemical Reaction with Cl2 at 1200° C.

(19) Useful as a carbide compound, TiC was thermally treated at 1500° C. for 4 hr in a vacuum, thus obtaining vacuum-treated TiC, which was then thermochemically reacted with Cl.sub.2 as a halogen element-containing gas at 1200° C. for about 3 hr and then annealed with H.sub.2 gas for about 2 hr, yielding vacuum-treated TiC-CDC.

(20) The process for reacting the carbide compound with the halogen element-containing gas to prepare CDC is represented by Scheme 1 below.
M.sub.aC.sub.b(s)+(c/2)Cl.sub.2(g).fwdarw.aMCl.sub.c↑(g)+bC↓(s)  [Scheme 1]

(21) In Scheme 1, M indicates a metal, C indicates carbon, and a, b and c indicate stoichiometric ratios.

Comparative Example 1: Preparation of TiC-CDC Via Thermochemical Reaction with Cl2 Gas at 1200° C.

(22) TiC-CDC was prepared by thermochemically reacting TiC as a carbide compound with Cl.sub.2 as a halogen element-containing gas at 1200° C. for about 3 hr.

Test Example 1: Measurement of N2 Adsorbed Amount and BET of Vacuum-Treated TiC-CDC and TiC-CDC

(23) The N.sub.2 adsorption curves of Example 1 and Comparative Example 1 were graphed. As illustrated in FIG. 1, the N.sub.2 adsorption curve of Example 1 showed a type-4 curve with adsorption/desorption hysteresis, corresponding to a mesoporous structure, and specific surface areas (BET areas) were 1264.8 m.sup.2/g and 1353.7 m.sup.2/g.

(24) Both Example 1 and Comparative Example 1 show type-4 curves corresponding to a mesoporous structure. The N.sub.2 adsorption curve of Example 1 was distributed at the low adsorbed amount compared to the N.sub.2 adsorption curve of Comparative Example 1 and thus had a small amount of mesopores. Such a reduction in the mesopores resulted in a decreased BET area, and Example 1 had a dense graphite structure and uniform crystallinity, compared to Comparative Example 1.

Test Example 2: Measurement of Pore Size Distribution of Vacuum-Treated TiC-CDC and TiC-CDC Via BJH and MP Analysis

(25) The adsorption results of Example 1 and Comparative Example 1 were analyzed using a BJH method. The pore size distributions thereof are illustrated in FIG. 2. Also, the pore size distributions thereof obtained via adsorption analysis using an MP method are illustrated in FIG. 3.

(26) As illustrated in FIGS. 2 and 3, Example 1 had nano-sized pores and exhibited a small pore distribution, compared to Comparative Example 1. This is because thermal treatment in a vacuum enables the carbide compound to be formed into a dense structure and then thermochemical reaction with the halogen element-containing gas enables the pore distribution to be reduced and the graphite crystallinity to become dense.

Test Example 3: XRD Measurement of Vacuum-Treated TiC-CDC and TiC-CDC

(27) To compare the structures of Example 1 and Comparative Example 1, the results of XRD measurement are illustrated in FIG. 4.

(28) As illustrated in FIG. 4, the peak of vacuum-treated TiC-CDC of Example 1 was 25.7°, which was shifted leftward compared to 26.3° that is the peak of TiC-CDC of Comparative Example 1. The lattice spacing of vacuum-treated TiC-CDC was larger than that of TiC-CDC.

Test Example 4: TEM Analysis of TiC, Vacuum-Treated TiC, Vacuum-Treated TiC-CDC, and TiC-CDC

(29) The TEM analytical results of the carbide compound (TiC), vacuum-treated carbide compound (vacuum-treated TiC), vacuum-treated carbide-derived carbon (vacuum-treated TiC-CDC), and carbide-derived carbon (TiC-CDC) are illustrated in FIGS. 5A to 5F.

(30) As illustrated in FIGS. 5A to 5F, when compared with TiC (FIGS. 5A and 5C), vacuum-treated TiC (FIGS. 5B and 5D) had high density due to the agglomeration of the particles into a dense structure. TiC-CDC exhibited a combination structure of an amorphous phase in various locations and graphite fringe therearound, with a porous structure. Vacuum-treated TiC-CDC manifested graphite fringe having a denser structure and thus had a small pore distribution compared to TiC-CDC. Therefore, vacuum-treated TiC-CDC can exhibit high graphite density and a large lattice spacing and thus high ion mobility.

(31) Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.