KR101274662B1 - Preparation method of multilayered carbon nano-fiber using electrospinning and multilayered carbon nano-fiber formed therefrom - Google Patents

Abstract

The present invention relates to a method for producing carbon nanofibers, comprising: (S1) a first polymer solution in which polyacrylonitrile is dissolved in a first solvent, and an acrylonitrile-containing copolymer having a pyrolysis temperature of 300 to 600 ° C. Preparing a second polymer solution dissolved in a solvent and a third polymer solution obtained by dissolving polyacrylonitrile in a third solvent; (S2) supplying the first polymer solution to a first nozzle, supplying the second polymer solution to a second nozzle surrounding the first nozzle, and supplying the third polymer solution to a third nozzle surrounding the second nozzle Supplying and simultaneously electrospinning to obtain a composite fiber including a core part-medium layer-shell layer; (S3) heat treating the composite fiber at a temperature lower than the thermal decomposition temperature of the acrylonitrile-containing copolymer to stabilize the polyacrylonitrile of the composite fiber; And (S4) calcining the resultant of (S3) to remove the acrylonitrile-containing copolymer by thermal decomposition while the stabilized polyacrylonitrile is carbonized.
According to the present invention, carbon nanofibers having a cross-section of a multi-layer structure can be easily manufactured by electrospinning a solution of a polyacrylonitrile and an acrylonitrile-containing copolymer having excellent affinity and high thermal stability. .

Description

Preparation method of multilayered carbon nano-fiber using electrospinning and multilayered carbon nano-fiber formed therefrom}

The present invention is a method of producing a multi-layer carbon nanofibers by complex electrospinning a solution of polyacrylonitrile (PAN), a precursor of carbon nanofibers with a heterogeneous polymer solution, and then removing the heterogeneous polymer through a sintering process. It relates to a multilayer carbon nanofiber formed from.

Carbon fibers are classified into polyacrylonitrile (PAN, polyacrylonitrile), pitch, and phenol based on starting materials. In particular, carbon fiber using polyacrylonitrile as a starting material has been attempted to be applied to various fields such as gas separation, water purification, catalyst, energy storage, and conversion devices due to its excellent electrical, thermal, and mechanical properties.

As a method for producing carbon fibers using polyacrylonitrile as a starting material, a solution obtained by dissolving polyacrylonitrile in a suitable solvent is spun through spinnerets to form a fibrous form, and then stabilized by heat treatment in an oxidizing gas atmosphere. And carbonized (or graphitized) the stabilized polyacrylonitrile by calcining in an inert atmosphere.

The carbon fiber produced by the conventional spinning method has a diameter of about 5-50 μm, and because of its large diameter, there is a limit in expressing physical properties specific to the carbon fiber. A method has been proposed. According to the carbon nanofiber manufacturing process using electrospinning, a polyacrylonitrile solution is spun through a spinning nozzle having a + (-) electrode, and then a suction collector having an electrode of opposite charge or grounding. The ultrafine fibers are collected to obtain carbon nanofibers through the stabilization-carbonization process described above. By such a method, carbon nanofibers can be obtained with ultra-fine fibers (nanofibers) of 1 µm or less.

However, since the carbon nanofibers produced by the above-described method have a circular cross-sectional shape, their use is limited, such as a small specific surface area and a limitation in performing the role of a carrier. Therefore, a technique for producing a cross section of carbon nanofibers in a C shape or a hollow shape to increase a specific surface area and to perform a role of a carrier has been proposed.

For example, Korean Patent No. 0783490 discloses a method of producing carbon nanofibers having a C-shaped cross section by simultaneously electrospinning a polyacrylonitrile solution and a polymethyl methacrylate solution. According to this manufacturing method, first, the polyacrylonitrile solution and the polymethyl methacrylate solution are composite electrospun with a Y-type nozzle so that the shell portion made of polyacrylonitrile partially covers the outer surface of the core portion made of polymethacrylate. After preparing the core-shell composite fiber, heat treating the core-shell composite fiber to stabilize the polyacrylonitrile, and calcining the same to thermally decompose the polymethacrylate while carbonizing the stabilized polyacrylonitrile to form a C-shaped cross section. Carbon nanofibers are obtained. This method is equally applicable to a method of producing carbon nanofibers having a hollow hollow cross section of a core part by using a nozzle in which the spun polyacrylonitrile solution is completely wrapped around the polymethacrylate solution.

However, when the composite electrospinning of the polyacrylonitrile solution and the polymethyl methacrylate solution is difficult, it is difficult to produce a uniform core-shell composite fiber because of poor radioactivity and high mixing between the two solutions. In addition, in the case of heat-treating the core-shell composite fiber to stabilize the polyacrylonitrile, the polymethyl methacrylate core portion having poor heat resistance does not function as a stable support, and thus it is difficult to obtain a carbon nanofiber having a desired cross section. That is, the stabilization process is performed at about 200 ° C. or more (typically selected at 350 ° C. or less), and the core part made of polymethyl methacrylate, which is poor in thermal stability, shrinks. Accordingly, since the polyacrylonitrile shell portion penetrates into the core portion during stabilization, the finally obtained carbon nanofibers have a very small hollow portion or are difficult to obtain carbon nanofibers having a C-shaped cross section.

In addition, the hollow carbon nanofibers or carbon nanofibers having a C-shaped cross section have limitations in application to various fields due to their shape.

Therefore, the problem to be solved by the present invention is a polyacrylonitrile as a precursor, a method for producing a carbon nanofiber having a multi-layer structure so that it can be applied to various fields and a multi-layered carbon nanofiber formed therefrom To provide.

Method for producing a multilayer carbon nanofiber according to the present invention to achieve the above object,

(S1) A first polymer solution in which polyacrylonitrile is dissolved in a first solvent, a second polymer solution in which an acrylonitrile-containing copolymer having a pyrolysis temperature of 300 to 600 ° C. is dissolved in a second solvent, and polyacrylonitrile. Preparing a third polymer solution in which nitriles are dissolved in a third solvent;

(S2) supplying the first polymer solution to a first nozzle, supplying the second polymer solution to a second nozzle surrounding the first nozzle, and supplying the third polymer solution to a third nozzle surrounding the second nozzle Supplying and simultaneously electrospinning to obtain a composite fiber including a core part-medium layer-shell layer;

(S3) heat treating the composite fiber at a temperature lower than the thermal decomposition temperature of the acrylonitrile-containing copolymer to stabilize the polyacrylonitrile of the composite fiber; And

(S4) calcining the resultant of (S3) such that the acrylonitrile-containing copolymer is thermally decomposed while the stabilized polyacrylonitrile is carbonized.

In the method for producing a multilayer carbon nanofiber of the present invention, the acrylonitrile-containing copolymer is a styrene-acrylonitrile copolymer, an acrylonitrile-butadiene-styrene copolymer, an acrylonitrile-butadiene copolymer, or a carboxylated acryl It is preferable to use a nitrile-butadiene copolymer, an acrylonitrile-isoprene copolymer, an acrylonitrile-styrene-acrylic copolymer, etc., individually or in mixture of two or more thereof.

In the carbon nanofiber manufacturing method of the present invention, the first solvent, the second solvent and the third solvent are independently of each other NN-dimethyl formamide, dimethyl sulfoxide, dimethyl acetamide, N-methylpyrrolidone, ethylene carbonate Etc. can be used individually or in mixture of 2 or more types of these, respectively. It is preferable to use the same solvent for a 1st solvent, a 2nd solvent, and a 3rd solvent.

In the carbon nanofiber manufacturing method of the present invention, a polymer having a pyrolysis temperature of 600 ° C. or less may be further dissolved in the first polymer solution, the third polymer solution, or both the first polymer solution and the third polymer solution. Such polymers may be used as long as the polymers have the above-described pyrolysis temperature range, such as polymethyl methacrylate, polyvinyl chloride, polyvinylacetate, polyvinylpyrrolidone, etc., but the pyrolysis temperature is 300 to 600 ° C. It is preferable that it is an acrylonitrile containing copolymer. In addition, polyacrylonitrile may be further dissolved in the second polymer solution, wherein the polyacrylonitrile content of the second polymer solution is higher than the polyacrylonitrile content of the first polymer solution and the third polymer solution. It can manufacture low, and it can also manufacture so that the polyacrylonitrile content of the said 1st polymer solution, the 2nd polymer solution, and the 3rd polymer solution may increase sequentially.

The second polymer solution may further disperse the fine powder of the electrode active material powder such as the positive electrode active material powder or the negative electrode active material powder. Such electrode active material powders include alloys and oxides containing at least one element selected from the group consisting of Si, Sn, Ge, Sb, Ti, In, Cu, Zr, Co, Fe, Ni, Mn, Zn, Ca, and V. Or sulfides may be used. In addition, it is possible to further disperse various materials that can be supported on the multi-layered carbon nanofiber of the present invention.

The diameter of the formed multi-walled carbon nanofibers is preferably 50 to 1000 nm, more preferably 50 to 500 nm. In addition, the core portion has a diameter of 10 to 450 nm, a medium layer having a thickness of 10 to 450 nm, and a shell layer having a thickness of 10 to 450 nm.

In the manufacturing method of the present invention, it is preferable that the first polymer solution and the second polymer solution are discharged through the first nozzle with shear force, and the third polymer solution is discharged with electrostatic repulsive force.

According to the above-described manufacturing method, it is possible to manufacture a multilayer carbon nanofibers having the following structure, but is not limited thereto.

A first aspect, comprising: (a) a carbon core portion extending in a longitudinal direction;

(b) a medium layer of an empty space formed to surround the carbon core part; And

(c) A multilayer carbon nanofiber having a carbon shell layer formed to surround the medium layer may be obtained.

Here, the medium layer may be a carbon bridge portion connecting the carbon core portion and the carbon shell layer to each other. In addition, the carbon core portion and the carbon shell layer may have pores.

Further, as a second aspect, (a) a carbon core portion extending in the longitudinal direction;

(b) a carbon medium layer formed to surround the carbon core part; And

(c) a carbon shell layer formed to surround the carbon medium layer,

The carbon medium layer may have multilayer carbon nanofibers having pores.

Here, the carbon core portion and the carbon shell layer may include pores, and the porosity of the carbon core portion, the carbon medium layer, and the carbon shell layer may be sequentially lowered.

According to the present invention, by spinning a solution of the acrylonitrile-containing copolymer having excellent affinity and high thermal stability with polyacrylonitrile and electrospinning, it is easy to spin the carbon nanofibers having a cross-section of a multi-layer structure Can be manufactured.

In addition, carbon nanofibers having pores may be prepared by adding an appropriate polymer in the manufacturing process, and may be used as an electrode of an electrochemical device by adding an electrode active material powder. In addition, various materials may be supported on the multilayer carbon nanotubes during or after the manufacturing process of the multilayer carbon nanotubes, thereby being applicable to various fields such as gas separation, water purification, catalysts, energy storage, and conversion devices.

The following drawings, which are attached to this specification, illustrate exemplary embodiments of the present invention, and together with the detailed description of the present invention, serve to facilitate understanding of the technical spirit of the present invention. It should not be construed as limited to matters.
1 is a schematic diagram schematically showing a cross section of a three-layer coaxial nozzle system for composite electrospinning in accordance with one embodiment of the present invention.
2 is a schematic cross-sectional view of a three-layer coaxial nozzle system for composite electrospinning in accordance with one embodiment of the present invention.
3 is a view showing the conditions of the stabilization and firing process according to the embodiment.
4 is a schematic diagram (a), TEM photograph (b) and SEM photograph (c) of multilayer carbon nanofibers obtained in Example 1. FIG.
FIG. 5 is a schematic diagram (a), TEM photograph (b) and SEM photograph (c) of multilayer carbon nanofibers obtained in Example 2. FIG.

Hereinafter, the present invention will be described in detail. The terms and words used in the present specification and claims should not be construed as limited to ordinary or dictionary terms and the inventor may appropriately define the concept of the term in order to best describe its invention It should be construed as meaning and concept consistent with the technical idea of the present invention.

Referring to the method for producing a multilayer carbon nanofiber of the present invention in detail as follows.

Method for producing a multilayer carbon nanofiber according to the present invention to achieve the above object,

 First, a first polymer solution in which polyacrylonitrile is dissolved in a first solvent, a second polymer solution in which an acrylonitrile-containing copolymer having a thermal decomposition temperature of 300 to 600 ° C. is dissolved in a second solvent, and polyacrylonitrile To prepare a third polymer solution dissolved in a third solvent.

The acrylonitrile-containing copolymer is a copolymer copolymerized with an acrylonitrile monomer such as polyacrylonitrile, and thus has good affinity with polyacrylonitrile. The inventors have found that these acrylonitrile-containing copolymers have very good radioactivity during complex electrospinning, unlike polymethylmethacrylate due to their affinity with polyacrylonitrile. That is, composite electrospinning of the polyacrylonitrile solution and the acrylonitrile-containing copolymer solution could easily produce a composite fiber having a uniform core-shell structure.

In addition, the acrylonitrile-containing copolymer used has a thermal decomposition temperature of 300 to 600 ° C., which is superior in thermal stability to polymethyl methacrylate. Since the stabilization process of polyacrylonitrile usually proceeds at 200 to 350 ° C. (most typically 300 ° C. or less), the acrylonitrile-containing copolymer has a pyrolysis temperature of at least 300 ° C. to prevent thermal decomposition in the stabilization process. In addition, the process of carbonizing stabilized polyacrylonitrile typically proceeds at temperatures above at least 600 ° C., thus acrylonitrile containing copolymers have a pyrolysis temperature of at most 600 ° C. Such acrylonitrile-containing copolymers include styrene-acrylonitrile copolymer, acrylonitrile-butadiene-styrene copolymer, acrylonitrile-butadiene copolymer, carboxylated acrylonitrile-butadiene copolymer, acrylonitrile-isoprene air A copolymer, an acrylonitrile-styrene-acryl copolymer, etc. can be mentioned, It can respectively use individually or in mixture of 2 or more types.

Thus, when heat-treating a composite fiber having a shell layer of a medium layer-polyacrylonitrile of a core-acrylonitrile-containing copolymer of polyacrylonitrile to stabilize polyacrylonitrile, heat resistance The excellent acrylonitrile-containing copolymer medium part, unlike polymethylmethacrylate, performs a stable support role with little shrinkage. Of course, the acrylonitrile-containing copolymer is not stabilized (incompatible) in the stabilization process by other copolymerized monomer components. That is, the medium layer of the acrylonitrile-containing copolymer is thermally decomposed and removed in the firing process for carbonization of the polyacrylonitrile described later. Accordingly, it is possible to easily obtain a multi-layered carbon nanofiber having a hollow cross section having a desired size.

In the carbon nanofiber manufacturing method of the present invention, the first solvent, the second solvent and the third solvent for dissolving the polyacrylonitrile and the acrylonitrile-containing copolymer, respectively, are independently of each other NN-dimethyl formamide, dimethyl sulfoxide. Said, dimethyl acetamide, N-methylpyrrolidone, ethylene carbonate, etc. can be used individually or in mixture of 2 or more of these, respectively. In order to further improve the affinity of the first polymer solution, the second polymer solution and the third polymer solution, it is preferable to use a solvent having high affinity for the first solvent, the second solvent, and the third solvent. It is more preferable to use.

In the carbon nanofiber manufacturing method of the present invention, a polymer having a pyrolysis temperature of 600 ° C. or less may be further dissolved in the first polymer solution, the third polymer solution, or both the first polymer solution and the third polymer solution. Such polymers may be used as long as the polymers have the above-described pyrolysis temperature range, such as polymethyl methacrylate, polyvinyl chloride, polyvinylacetate, polyvinylpyrrolidone, etc., but the pyrolysis temperature is 300 to 600 ° C. It is preferable that it is an acrylonitrile containing copolymer. Since the polymer having a thermal decomposition temperature of 600 ° C. or less dissolved in the first polymer solution, the third polymer solution, or both thereof is pyrolyzed and removed during the sintering process, pores may be formed in the core part and the shell layer. In particular, when using the acrylonitrile-containing copolymer having a pyrolysis temperature of 300 to 600 ℃ as such a polymer, it is not removed in the stabilization process of polyacrylonitrile may not impair the object of the present invention.

In addition, polyacrylonitrile may be further dissolved in the second polymer solution. Thus, after the firing process, the medium layer is not formed as an empty space, but a portion where the polyacryl is carbonized remains. The shape of the medium layer is changed according to the amount of polyacrylonitrile added to the second polymer solution. For example, when the amount of polyacrylonitrile is added in an amount of 1/3 of the polyacrylonitrile-containing copolymer, The medium layer may include a carbon bridge portion connecting the carbon core portion and the carbon shell layer to each other. Of course, the space other than the carbon bridge portion remains empty. In addition, when a large amount of polyacrylonitrile is added, a structure in which pores are formed in the carbon structure such as the core portion and the shell layer is formed. That is, the polyacrylonitrile content of the second polymer solution may be lower than the polyacrylonitrile content of the first polymer solution and the third polymer solution to form a medium layer having a bridge portion, and the first polymer solution Also, the polyacrylonitrile content of the second polymer solution and the third polymer solution may be sequentially increased to produce carbon nanofibers having a three-layer carbon structure in which the porosity of the core portion, the medium layer, and the shell layer is gradually lowered. have.

The second polymer solution may further disperse the fine powder of the electrode active material powder such as the positive electrode active material powder or the negative electrode active material powder. Such electrode active material powders include alloys and oxides containing at least one element selected from the group consisting of Si, Sn, Ge, Sb, Ti, In, Cu, Zr, Co, Fe, Ni, Mn, Zn, Ca, and V. Or sulfides may be used. The acrylonitrile-containing copolymer is removed through the firing process, but the electrode active material powder remains on the inner surface of the multilayer carbon nanofibers. Thereby, it can be used as an electrode of an electrochemical element. In particular, since the silicon anode has a large volume change during charge and discharge, its use as a cathode has been limited, and the silicon anode material located between the core portion and the shell layer of the multilayer carbon nanofibers can be controlled by the carbon nanofibers. In particular, since the core portion of the multi-layered carbon nanofibers can act as a conducting pass, ion conductivity can be maintained smoothly. In addition, it is possible to further disperse various materials that can be supported on the multi-layered carbon nanofiber of the present invention, the material that can be destroyed in the firing process can be supported by a variety of known methods after manufacturing the multi-layered carbon nanofibers Of course.

Subsequently, the first polymer solution is supplied to a first nozzle, the second polymer solution is supplied to a second nozzle surrounding the first nozzle, and the third polymer solution is supplied to a third nozzle surrounding the second nozzle. Simultaneously feeding and electrospinning yields a composite fiber comprising a core portion-a medium layer-a shell layer (step S2).

The method of obtaining a composite fiber having such a shape can be obtained by electrospinning using a three-layer coaxial nozzle designed as shown in FIGS. 1 and 2. That is, a second nozzle for supplying the first polymer solution to a first nozzle (a portion indicated by the cores of FIGS. 1 and 2) using a three-layer coaxial nozzle having the illustrated nozzle gauge, and surrounding the first nozzle. The second polymer solution is supplied to (parts indicated by medium of FIGS. 1 and 2), and the third polymer solution is supplied to a third nozzle (parts labeled shell in FIGS. 1 and 2) surrounding the second nozzle. By simultaneously supplying and electrospinning, a composite fiber comprising a core portion, a medium layer, and a shell layer can be obtained. In this case, it is preferable that the first polymer solution and the second polymer solution are discharged through the first nozzle with shear force, and the third polymer solution is discharged with electrostatic repulsive force.

The composite fiber formed by electrospinning is heat treated at a temperature lower than the pyrolysis temperature of the acrylonitrile-containing copolymer to stabilize the polyacrylonitrile present in the core-media layer-shell layer composite fiber (step S3).

As described above, the stabilization process of polyacrylonitrile is usually carried out at 200 to 350 ° C. (most typically 300 ° C. or less) in an oxidizing atmosphere such as in air, so that the acrylonitrile-containing copolymer should not be pyrolyzed in the stabilization process. The stabilization process temperature is carried out at a temperature lower than the pyrolysis temperature of the acrylonitrile containing copolymer used. Through the stabilization process the polyacrylonitrile is stabilized (infused), and the acrylonitrile containing copolymer is not stabilized (incompatible) in the stabilization process by other copolymerized monomer components.

Subsequently, the resultant of (S3) is fired so that the acrylonitrile-containing copolymer is thermally decomposed and the stabilized polyacrylonitrile is carbonized. Accordingly, the multi-layered carbon nanofibers according to the present invention are produced (step S4). The firing process may proceed in accordance with conventional conditions. For example, firing is performed at an inert gas atmosphere at a temperature of 700 to 3000 ° C, more preferably about 1000 ° C or more. The core part and the shell layer made of polyacrylonitrile stabilized by the firing process are carbonized (including graphite), and the medium part made of acrylonitrile-containing copolymer is thermally decomposed and removed. If the core portion or cell layer contains an acrylonitrile-containing copolymer, pores are formed upon thermal decomposition of the contained acrylonitrile-containing copolymer. In addition, if the polyacrylonitrile is included in the medium portion, as described above, a medium portion having a structure in which pores are formed in the carbon structure, such as the core portion and the shell layer, may be formed according to the content ratio. That is, the polyacrylonitrile content of the second polymer solution may be lower than the polyacrylonitrile content of the first polymer solution and the third polymer solution to form a medium layer having a bridge portion, and the first polymer solution Also, the polyacrylonitrile content of the second polymer solution and the third polymer solution may be sequentially increased to produce carbon nanofibers having a three-layer carbon structure in which the porosity of the core portion, the medium layer, and the shell layer is gradually lowered. have.

According to such process conditions, it is possible to manufacture a multi-layered carbon nanofibers typically having the following structure.

A first aspect, comprising: (a) a carbon core portion extending in a longitudinal direction;

(b) a medium layer of an empty space formed to surround the carbon core part; And

(c) A multilayer carbon nanofiber having a carbon shell layer formed to surround the medium layer may be obtained.

Here, the medium layer may be a carbon bridge portion connecting the carbon core portion and the carbon shell layer to each other. In addition, the carbon core portion and the carbon shell layer may have pores.

Further, as a second aspect, (a) a carbon core portion extending in the longitudinal direction;

(b) a carbon medium layer formed to surround the carbon core part; And

(c) a carbon shell layer formed to surround the carbon medium layer,

The carbon medium layer may have multilayer carbon nanofibers having pores.

Here, the carbon core portion and the carbon shell layer may include pores, and the porosity of the carbon core portion, the carbon medium layer, and the carbon shell layer may be sequentially lowered.

The diameter of the formed multi-walled carbon nanofibers is preferably 50 to 1000 nm, more preferably 50 to 500 nm. In addition, the core portion has a diameter of 10 to 450 nm, a medium layer having a thickness of 10 to 450 nm, and a shell layer having a thickness of 10 to 450 nm. The diameter of the core portion, the thickness of the medium layer and the shell layer may be changed by adjusting the diameter of the nozzle, the concentration of the polyacrylonitrile or acrylonitrile copolymer contained in the polymer solutions, the spinning flow rate, and the like.

Hereinafter, the present invention will be described with reference to Examples. However, embodiments according to the present invention can be modified in many different forms, the scope of the invention should not be construed as limited to the following examples. Embodiments of the present invention are provided to more fully describe the present invention to those skilled in the art.

Example  One

Polyacrylonitrile was dissolved in N-N-dimethyl formamide to prepare a 20 wt% first polymer solution. A styrene-acrylonitrile copolymer having a pyrolysis temperature of about 400 ° C. was dissolved in N-N-dimethyl formamide at a concentration of 30 wt%, and then 5 wt% of silicon nanopowder was dispersed therein to prepare a second polymer solution. In addition, polyacrylonitrile was dissolved in N-N-dimethyl formamide to prepare a 20 wt% third polymer solution.

Subsequently, the prepared first polymer solution, second polymer solution and third polymer solution were prepared using a three-layer coaxial nozzle system (needle gauge: core-22GP, medium-17GP, shell-17GP) shown in FIGS. 1 and 2. The first polymer solution and the second polymer solution were discharged through the first nozzle with shear force, and the third polymer solution was discharged with electrostatic repulsive force to electrospin.

The core is electrospun into a rotating cylindrical collector with a diameter of 30 cm under the conditions of an applied voltage of 18 KV, a spinning distance of 15 cm, a flow rate of core portion 0.15 ml / h, a medium layer flow rate of 0.25 ml / h, and a shell layer flow rate of 0.5 ml / h. Shell-type composite fibers were prepared.

Subsequently, the stabilization and firing processes were performed under the conditions shown in FIG. 3. The schematic diagram (a), the TEM photograph (b), and the SEM photograph (c) of the obtained multilayer carbon nanofiber are shown in FIG.

Example  2

Polyacrylonitrile was dissolved in N-N-dimethyl formamide to prepare a 20 wt% first polymer solution. A second polymer solution was prepared by dissolving a styrene-acrylonitrile copolymer having a thermal decomposition temperature of about 400 ° C. and polyacrylonitrile in a concentration of 30 wt% in N-N-dimethyl formamide in a weight ratio of 3: 1. In addition, polyacrylonitrile was dissolved in N-N-dimethyl formamide to prepare a 20 wt% third polymer solution.

Subsequently, the prepared first polymer solution, second polymer solution and third polymer solution were prepared using a three-layer coaxial nozzle system (needle gauge: core-22GP, medium-17GP, shell-17GP) shown in FIGS. 1 and 2. The first polymer solution and the second polymer solution were discharged through the first nozzle with shear force, and the third polymer solution was discharged with electrostatic repulsive force to electrospin.

The core is electrospun into a rotating cylindrical collector with a diameter of 30 cm under the conditions of an applied voltage of 18 KV, a spinning distance of 15 cm, a flow rate of core portion 0.15 ml / h, a medium layer flow rate of 0.25 ml / h, and a shell layer flow rate of 0.5 ml / h. Shell-type composite fibers were prepared.

Subsequently, the stabilization and firing processes were performed under the conditions shown in FIG. 3. The schematic diagram (a), the TEM photograph (b), and the SEM photograph (c) of the obtained multilayer carbon nanofiber are shown in FIG.

Claims (20)

(S1) A first polymer solution in which polyacrylonitrile is dissolved in a first solvent, a second polymer solution in which an acrylonitrile-containing copolymer having a pyrolysis temperature of 300 to 600 ° C. is dissolved in a second solvent, and polyacrylonitrile. Preparing a third polymer solution in which nitriles are dissolved in a third solvent;
(S2) supplying the first polymer solution to a first nozzle, supplying the second polymer solution to a second nozzle surrounding the first nozzle, and supplying the third polymer solution to a third nozzle surrounding the second nozzle Supplying and simultaneously electrospinning to obtain a composite fiber including a core part-medium layer-shell layer;
(S3) heat treating the composite fiber at a temperature lower than the thermal decomposition temperature of the acrylonitrile-containing copolymer to stabilize the polyacrylonitrile of the composite fiber; And
(S4) The stabilized polyacrylonitrile is carbonized, the acrylonitrile-containing copolymer comprises the step of firing the product of the (S3) to be removed by thermal decomposition, a method for producing a multilayer carbon nanofiber. The method of claim 1,
The acrylonitrile-containing copolymer includes styrene-acrylonitrile copolymer, acrylonitrile-butadiene-styrene copolymer, acrylonitrile-butadiene copolymer, carboxylated acrylonitrile-butadiene copolymer, acrylonitrile isoprene-air Method for producing a multilayer carbon nanofiber, characterized in that any one or a mixture of two or more selected from the group consisting of a copolymer and an acrylonitrile-styrene-acryl copolymer. The method of claim 1,
The first solvent, the second solvent and the third solvent are each independently selected from the group consisting of NN-dimethyl formamide, dimethyl sulfoxide, dimethyl acetamide, N-methylpyrrolidone and ethylene carbonate or two of them Method of producing a multilayer carbon nanofiber, characterized in that the mixture of species or more. The method according to claim 1 or 3,
The first solvent, the second solvent and the third solvent is the same solvent, characterized in that the manufacturing method of the multilayer carbon nanofibers. The method of claim 1,
A method for producing multilayer carbon nanofibers, further comprising dissolving a polymer having a thermal decomposition temperature of 600 ° C. or lower in the first polymer solution, the third polymer solution, or both the first polymer solution and the third polymer solution. The method of claim 5,
The polymer having a pyrolysis temperature of 600 ° C. or less is an acrylonitrile-containing copolymer having a pyrolysis temperature of 300 to 600 ° C., wherein the method for producing multilayer carbon nanofibers. 6. The method according to claim 1 or 5,
The polyacrylonitrile is further dissolved in the second polymer solution. The method of claim 7, wherein
The polyacrylonitrile content of the second polymer solution is lower than the polyacrylonitrile content of the first polymer solution and the third polymer solution. The method of claim 7, wherein
The polyacrylonitrile content of the first polymer solution, the second polymer solution and the third polymer solution is sequentially increased, the method for producing multilayer carbon nanofibers. The method of claim 1,
The electrode active material powder is further dispersed in the second polymer solution, characterized in that the manufacturing method of the multilayer carbon nanofibers. The method of claim 10,
The electrode active material powder is an alloy, an oxide containing any one or more elements selected from the group consisting of Si, Sn, Ge, Sb, Ti, In, Cu, Zr, Co, Fe, Ni, Mn, Zn, Ca and V Method for producing a multilayer carbon nanofiber, characterized in that the sulfide. The method of claim 1,
The diameter of the multilayer carbon nanofibers is 50 to 1000nm, characterized in that the manufacturing method of the multilayer carbon nanofibers. 13. The method according to claim 1 or 12,
The diameter of the core portion is 10 to 450nm, the thickness of the medium layer is 10 to 450nm, the thickness of the shell layer is characterized in that 10 to 450nm, the method for producing multi-layer carbon nanofibers. The method of claim 1,
Wherein the first polymer solution and the second polymer solution are discharged through the first nozzle with shear force, and the third polymer solution is discharged with electrostatic repulsive force. (a) a longitudinally extending carbon core portion;
(b) a medium layer of an empty space formed to surround the carbon core part; And
(c) a multilayer carbon nanofiber having a carbon shell layer formed to surround the medium layer. 16. The method of claim 15,
The medium layer is a multi-layered carbon nanofibers, characterized in that the carbon bridge portion is formed to connect the carbon core portion and the carbon shell layer. 16. The method of claim 15,
The carbon core part and the carbon shell layer is characterized in that the multi-layered carbon nanofibers characterized in that the pores. (a) a longitudinally extending carbon core portion;
(b) a carbon medium layer formed to surround the carbon core part; And
(c) a carbon shell layer formed to surround the carbon medium layer,
The carbon medium layer is multi-layered carbon nanofibers, characterized in that it comprises pores. 19. The method of claim 18,
The carbon core part and the carbon shell layer is characterized in that the multi-layered carbon nanofibers characterized in that the pores. 20. The method of claim 19,
Multi-layer carbon nanofibers, characterized in that the porosity of the carbon core portion, the carbon medium layer and the carbon shell layer is sequentially lowered.

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