KR102372233B1 - Manufacturing methods and electrode material applications of poly(ether amide)-based carbon nanofibers - Google Patents

Abstract

The present invention relates to a poly(ether-amide)-based polymer based carbon nanofiber and a manufacturing method therefor. More specifically, the present invention provides a method for manufacturing a carbon nanofiber doped with molecular sieve nitrogen by carbonizing a poly(ether-amide)-based aromatic polymer based nanofiber precursor, and a use as an electrode material thereof, wherein the electrode material has a higher capacitance and a higher energy density compared with those of existing carbon-based electrode materials.

Description

{Manufacturing methods and electrode material applications of poly(ether amide)-based carbon nanofibers}

The present invention relates to aromatic polyetheramide polymer-based carbon nanofibers and a method for manufacturing the same, and more particularly, to carbon nanofibers produced by carbonizing a nanofiber precursor based on aromatic polyetheramide polymers and an electrode material having high energy density thereof It provides an application method as

Recently, the demand for next-generation energy storage devices requiring high performance is continuously expanding due to the rapid growth and dissemination of new renewable energy, portable personal multimedia devices such as smart devices, and hybrid vehicle markets. Most of the recent next-generation energy storage systems are based on electrochemical principles, and examples thereof include lithium-based secondary batteries and electrochemical capacitors.

Supercapacitors belonging to the secondary battery category have higher power density, lower charging time, near-unlimited continuous charge/discharge lifespan, and eco-friendly characteristics compared to lithium-ion batteries, but have the disadvantage of low energy density. Because of these characteristics, they are widely used in smart phones, smart pads, memory storage devices, electric vehicles, and industrial energy storage devices. there is.

Supercapacitors are representative of electric double-layer capacitors using the electric double-layer principle and pseudo-capacitors using the oxidation-reduction principle. As electrode materials for these capacitors, conductive polymers, metal oxides, graphite, carbon materials such as graphene, etc. are mainly used. there is.

The electrospinning method is widely used as an easy method to increase the surface area of carbon materials. When the carbonization process is applied to this, the diameter of the fiber decreases and the surface area to volume ratio becomes wider, and numerous pores are created, thereby exhibiting high electrochemical performance. Active research is being conducted.

Moreover, nanofibers manufactured through electrospinning are significantly cheaper than nanofibers manufactured by wet spinning, melt spinning, and dry spinning, and if soluble in a solvent, a polymer can be prepared as a solution and electrospun.

In addition, the electrospinning method is simpler than other methods and has the advantage of being able to manufacture fibers having a large specific surface area, but still requires improvement of electrochemical properties in order to be used as an electrode material for an energy storage device.

To this end, if the carbon material is doped with a hetero element, high capacitance and electrochemical performance can be improved, but there is a disadvantage that the price of the electrode material is increased because a doping process must be added, and performance improvement is still required.

Recognizing this problem, the inventors of the present invention developed an electrode material having a high electric capacity without a process of doping a hetero element after processing a carbon material having a high specific surface area into an electrode shape. As a result, it exhibited higher capacitance and higher energy density than conventional carbon fibers.

)를 갖는 방향족 폴리에테르아마이드계 고분자를 기반으로 하여 전기방사한 후 탄화할 경우, 통상의 흑연소재의 전극 소재를 사용하는 경우 보다 2배, 좋게는 2.5배 이상의 현저히 높은 정전용량을 가짐과 동시에 슈퍼커패시터의 단점이라고 할 수 있는 낮은 에너지밀도를 보완하였으며, 질소가 도핑된 탄소나노섬유 형태의 전극 소재를 제조할 수 있음을 발견하여 본 발명을 완성하였다.The inventors of the present invention surprisingly, an ether group (-O-) and an amide group (

) based on an aromatic polyetheramide-based polymer with electrospinning and carbonization, it has a significantly higher capacitance 2 times, preferably 2.5 times or more, than when using a conventional graphite electrode material, and at the same time super The present invention was completed by discovering that the low energy density, which can be said to be a disadvantage of the capacitor, could be supplemented, and that an electrode material in the form of carbon nanofibers doped with nitrogen could be manufactured.

Republic of Korea Patent Publication No. 10-0754375 B1 (2007.08.27)

The present invention is that by carbonizing the aromatic polyetheramide-based nanofiber precursor prepared by electrospinning, it is possible to manufacture a carbon nanofiber-based electrode material with improved conductivity and superior electric capacity than conventional carbon nanofibers. found In addition, it is possible to provide an electrode material for an energy storage device (capacitor and secondary battery) manufactured by using this as an electrode material.

Embodiments of the present invention for achieving the above object are as follows.

The method for producing carbon nanofibers includes: a) electrospinning a spinning solution containing a polyetheramide-based polymer and a solvent to prepare a polyetheramide-based nanofiber precursor; and

b) carbonizing the polyetheramide-based nanofiber precursor to prepare nitrogen-doped carbon nanofibers.

According to the present invention, the polyetheramide-based polymer of step a) includes repeating units represented by the following Chemical Formulas 1 and 2, and the polyetheramide-based polymer is a block copolymer or a random copolymer. can

[Formula 1]

[Formula 2]

According to an embodiment of the present invention, the spinning solution may include a mixture of a porosity forming agent and a polyetheramide-based polymer.

According to an embodiment of the present invention, the porosity forming agent may include at least one selected from an acrylic copolymer and a water-soluble polymer.

According to an embodiment of the present invention, the spinning solution may include a mixture of the polyetheramide polymer and the porosity forming agent in a weight ratio of 0.3 to 1.0: 0.7 to 0.0.

According to an embodiment of the present invention, the solvent is N-methyl-2-pyrrolidone, dimethylacetamide, dimethylformamide, dimethylsulfoxide, ethanol, acetone, tetrahydrofuran, isopropanol, formic acid, chloroform, benzene, phenol , may include one or more selected from the group consisting of carbon tetrachloride, cresol, water, sulfuric acid, hydrochloric acid and nitric acid.

According to an example of the present invention, the electrospinning may include performing at a voltage of 1 to 1,000 kV and a flow rate of 0.01 to 1,000 ml/h.

According to an example of the present invention, the carbonization of step b) may include being performed at a temperature of 500 to 2,500 ℃.

Carbon nanofibers according to the present invention may include those produced by the method for producing carbon nanofibers.

According to an embodiment of the present invention, the carbon nanofibers may include nitrogen in an amount of 0.1 to 10.0 atomic%.

The carbon nanofibers according to the present invention may include those having a specific capacity of 50 to 500 F/g, an energy density of 1 to 900 Wh/kg, and a power density of 100 to 50,000 W/kg.

The electrode material for an energy storage device according to the present invention includes one made of the carbon nanofibers.

The electrode material for the energy storage device according to an embodiment of the present invention may include an electric double layer capacitor, a hybrid capacitor, a lithium secondary battery, a solar cell, a fuel cell, and the like.

The method of manufacturing carbon nanofibers according to an embodiment of the present invention has the advantage that an electrode material having high power density and energy density can be manufactured by carbonizing the polyetheramide-based nanofiber precursor prepared by electrospinning.

The method of manufacturing carbon nanofibers according to an embodiment of the present invention has the advantage that it can be dissolved in an organic solvent, can manufacture carbon nanofibers without a separate stabilization process, and can simplify the process.

The electrode material for an energy storage device according to an embodiment of the present invention has the advantage of having a high electric capacity and excellent electrochemical performance by using carbon nanofibers prepared by carbonizing a polyetheramide-based nanofiber precursor as an electrode material. , which surprisingly shows higher power density and energy density than conventional carbon nanofibers.

When used in an energy storage device, the electrode material for an energy storage device according to an embodiment of the present invention has advantages of stable electrochemical performance, high electrical capacity, and excellent energy density.

As can be seen in FIG. 6, the electric capacity of the carbon nanofibers of the present invention is 459.8 F/g at a specific current of 1 A/g, and 420.3 F at a specific current of 2 A/g. In view of the fact that the specific capacity of the conventional graphite material represents 150 to 200 F/g at a specific current of 1 A/g, it is possible to bring about a significant increase in capacitance by 2 times, preferably 2.5 times or more. There are advantages.

Even if effects not explicitly mentioned in the present invention, the effects described in the specification expected by the technical features of the present invention and the inherent effects thereof are treated as described in the specification of the present invention.

1 (a) a polyetheramide-based nanofiber precursor and b) carbon nanofibers are photographs observed with a scanning electron microscopy (SEM).
Figure 2 shows the results of Raman spectroscopy (Raman Spectroscopy) analysis of carbon nanofibers according to an embodiment of the present invention.
FIG. 3 shows the results of Energy Dispersive X-ray Spectroscopy analysis of carbon nanofibers according to an embodiment of the present invention.
FIG. 4 shows the measurement results of a cyclic voltagram using a three-electrode system when carbon nanofibers according to an embodiment of the present invention are used as an electrode material for a capacitor.
5 is a graph showing the results of charging and discharging experiments using a three-electrode system when carbon nanofibers according to an embodiment of the present invention are used as an electrode material for a capacitor.
6 shows the measurement results of capacitance, that is, specific capacitance, from the results of charging and discharging experiments when carbon nanofibers according to an embodiment of the present invention are used as a capacitor electrode material.
7 is a graph showing measurement results of energy density and power density obtained from specific capacity when carbon nanofibers according to an embodiment of the present invention are used as a capacitor electrode material.

Hereinafter, the present invention will be described in more detail through embodiments or examples including the accompanying drawings. However, the following specific examples or examples are only a reference for describing the present invention in detail, and the present invention is not limited thereto, and may be implemented in various forms.

Also, unless defined otherwise, all technical and scientific terms have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description herein is for the purpose of effectively describing particular embodiments only and is not intended to limit the invention.

Also, the singular forms used in the specification and appended claims may also be intended to include the plural forms unless the context specifically dictates otherwise.

In addition, in the present invention, the unit of % used unclearly without special mention means % by weight.

)를 갖는 방향족 고분자로서, 일 예로 하기 화학식 1 또는 하기 화학식 2의 반복단위를 갖는 블록 공중합체 또는 랜덤 공중합체를 의미할수 있다. The term “polyetheramide-based polymer” used in the present invention refers to an ether group and an amide group (

) as an aromatic polymer having, for example, may refer to a block copolymer or a random copolymer having a repeating unit of Formula 1 or Formula 2 below.

[Formula 1]

[Formula 2]

The repeating units of Formulas 1 and 2 may have a molar ratio of 0.01 to 0.99: 0.99 to 0.01, but is not limited thereto.

The inventor of the present invention uses a polyetheramide-based polymer containing a plurality of aromatics as shown in the above structural formula, so that a carbonization process that does not require a stabilization step in manufacturing carbon nanofibers using the same can be performed, so polyacrylic, a precursor of an existing carbon material It was found that it is economical because it is simpler than carbonization processes such as ronitrile, cellulose, and pitch.

The term “electrospinning” used in the present invention is a process capable of manufacturing an electrically charged polymer solution and melt into nanofibers through a jet-type nozzle. This electrospinning method is a technology that can easily manufacture any polymer material that can be melted or dissolved into nanofibers and can control the shape and size of nanofibers.

As used herein, the term “capacitor” is a device capable of storing electricity and is also referred to as a capacitor. A capacitor basically has a structure in which two electrode plates face each other, and when a DC voltage is applied thereto, electric charges are accumulated in each electrode. A capacitor is a type of energy storage device that is widely used together with a secondary battery. A supercapacitor, which is a capacitor with a very large storage capacity, is characterized by a large energy density and output and a short charge/discharge time compared to a lithium ion secondary battery.

The inventors of the present invention have prepared a nanofiber precursor by electrospinning the polyetheramide-based polymer of the present invention containing a plurality of aromatics and carbonizing it, the stabilization process can be omitted, and the conventional electrospinning method The present invention was completed by discovering that it can have superior capacitance and high energy density compared to carbon nanofibers.

Therefore, when the carbon nanofibers prepared from the polyetheramide-based nanofiber precursor of the present invention are used as an electrode material for an energy storage device, there is an advantage of having a high electrostatic capacity and excellent electrochemical properties. The reason for such excellent properties is that it has pores due to excellent conductivity and carbonization, and is doped with nitrogen to increase active sites, which leads to high interaction with electrolytes. Moreover, it has a surprising effect in that it has better electric capacity and energy density than conventional carbon nanofibers.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated concretely.

The method for producing carbon nanofibers according to the present invention comprises the steps of: a) preparing a polyamide-based nanofiber precursor by electrospinning a spinning solution containing a polyetheramide-based polymer and a solvent; and b) the polyetheramide-based nanofiber precursor and carbonizing to prepare carbon nanofibers.

Step a) includes preparing a polyetheramide-based nanofiber precursor by electrospinning a spinning solution containing a polyetheramide-based polymer and a solvent.

The polyetheramide-based polymer in step a) may be a polyetheramide polymer including repeating units represented by the following Chemical Formulas 1 and 2.

[Formula 1]

[Formula 2]

The repeating units of Formulas 1 and 2 may have a molar ratio of 0.01 to 0.99: 0.99 to 0.01, but is not limited thereto.

The solvent can dissolve the polyetheramide-based polymer, and is not particularly limited as long as it is a material used in the art, but specifically, for example, N-methyl-2-pyrrolidone, dimethylacetamide, dimethylformamide, At least one selected from the group consisting of dimethyl sulfoxide, ethanol, acetone, isopropanol, formic acid, chloroform, benzene, phenol, carbon tetrachloride, cresol, water, sulfuric acid, hydrochloric acid and nitric acid may be used.

The solid content of the spinning solution is not particularly limited, but may be in the range of 1 to 50% by weight, specifically 5 to 30% by weight, and in the composition ratio, the viscosity and smooth electrospinning of the spinning solution are It may be possible, but is not limited to the composition ratio.

The spinning solution may be prepared by mixing and stirring a polyetheramide-based polymer and a solvent, and preferably, a polyetheramide-based polymer and a solvent are mixed at 20 to 100° C. for 1 minute to 24 hours. and stirring to prepare the spinning solution, but is not limited thereto.

In addition, the spinning solution may be mixed with a porosity forming agent and a polyetheramide-based polymer.

The porosity forming agent may have an effect of further improving the surface area of the carbon nanofibers by increasing the pore area and number in the carbonization process of the polyetheramide-based nanofiber precursor.

The porosity forming agent may be at least one selected from an acrylic copolymer and a water-soluble polymer, but is not limited thereto.

The polyetheramide polymer and the porosity forming agent may be mixed in a weight ratio of 0.3 to 1.0: 0.7 to 0.0, preferably 0.6 to: may be mixed in a weight ratio of 0.4 to 0.2, more preferably 0.6 to 0.7: may be a mixture of 0.4 to 0.3, but is not limited thereto.

As the polyetheramide polymer and the porosity former are mixed within the above range, the specific surface area of the carbon nanofibers increased after carbonization, when used as an electrode material, the specific capacity and energy density, etc. can be further improved.

The polyetheramide-based nanofiber precursor of the present invention can be prepared by electrospinning the spinning solution.

The electrospinning is not particularly limited as long as it is a voltage condition capable of producing the desired polyetheramide-based nanofiber precursor of the present invention, but 1 to 100 kV, specifically 1 to 50 kV, more specifically 1 to 30 kV can As a specific example, the voltage is preferably performed at 1 to 30 kV in that the polyetheramide-based nanofiber precursor of the present invention can be easily formed.

The electrospinning is not particularly limited and may be 0.01 to 1,000 ml/h, specifically 0.1 to 500 ml/h, more specifically, as long as the flow rate conditions for preparing the polyetheramide-based nanofiber precursor for the present invention are It may be 0.2 to 100 ml/h, but various adjustments are possible as needed.

The electrospinning may be 1 to 50 cm between the syringe tip and the collector, specifically 5 to 40 cm, more specifically 10 to 30 cm, and as a specific example, it is performed at 10 to 25 cm. It is preferable in that the formation of the etheramide-based nanofiber precursor can be easy.

The diameter of the polyetheramide-based nanofiber precursor prepared by spinning the spinning solution by electrospinning under the above conditions is not particularly limited because it can be appropriately adjusted to suit the thickness of the required electrode material for the energy storage device, but, for example, For example, a diameter of 1 to 500 nm, preferably about a diameter of 10 to 300 nm, but is not particularly limited thereto.

The polyetheramide-based nanofiber precursor may be in the form of a nanofiber mat or a nanofiber membrane.

The polyetheramide-based nanofiber precursor prepared in step a) is a precursor of the nitrogen-doped carbon nanofibers of the present invention and can be obtained as nitrogen-doped carbon nanofibers by a subsequent carbonization process.

Next, step b) will be described.

Step b) includes carbonizing the polyetheramide-based nanofiber precursor to prepare nitrogen-doped carbon nanofibers.

The carbonization of step b) is not particularly limited as long as the temperature at which the polyetheramide-based nanofiber precursor can be carbonized, but may be performed at a temperature of 500 to 2,500 ℃, specifically 500 to 2,000 ℃, more specifically As such, it may be carried out at 500 to 1,500 °C. In addition, the carbonization temperature is good because it is a temperature at which graphitization and nitrogen doping of the polyetheramide-based nanofiber precursor can be stably performed, and more preferably 700 to 1,300 in consideration of improved high electric capacity and electrochemical properties. It is preferably carried out at a temperature of °C.

The atmospheric atmosphere in the carbonization of step b) is not particularly limited, but may be, for example, an atmosphere including any one or two or more selected from vacuum, argon, nitrogen, oxygen, carbon monoxide, carbon disulfide and carbon dioxide, etc. Of course, this is merely an example, and the present invention is not limited thereto.

The polyetheramide-based nanofiber precursor has activated carbon and graphite structures through the carbonization of step b), and can be obtained as nitrogen-doped carbon nanofibers.

Carbon nanofibers according to an aspect of the present invention include those produced by the method for producing carbon nanofibers.

The carbon nanofibers are not limited in shape, but may be in the form of a mat or a membrane in order to have the desired electrode performance of the present invention.

The diameter of the carbon nanofiber may be appropriately adjusted to suit the thickness of the required electrode material for an energy storage device, and the diameter may be reduced compared to the polyetheramide-based nanofiber precursor through carbonization. Specifically, the diameter of the carbon nanofibers may have a diameter of 1 to 300 nm, preferably, a diameter of 10 to 250 nm, but is not particularly limited thereto.

The carbon nanofibers prepared from the polyetheramide-based nanofiber precursor may themselves contain 0.1 to 10 atomic % of nitrogen by the carbonization, specifically 0.1 to 8 atomic %, more specifically 0.1 to 6 atomic % It may contain atomic percent nitrogen atoms.

The electrode material for an energy storage device according to an aspect of the present invention includes one made of the carbon nanofibers.

In the electrode material for an energy storage device according to an aspect of the present invention, the energy storage device includes an electric double layer capacitor, a hybrid capacitor, a lithium secondary battery, a solar cell, a fuel cell, and the like.

Specifically, the electrode material for the energy storage device made of the carbon nanofibers may be used for energy storage devices such as electric double layer capacitors, hybrid capacitors, lithium secondary batteries, solar cells, and fuel cells.

Nitrogen-doped carbon nanofibers produced by the method for producing carbon nanofibers of the present invention have excellent electric capacity, charge/discharge characteristics and electrochemical properties, and thus can be used as an electrode material for an energy storage device.

In particular, when the carbon nanofiber of the present invention is used as an electrode material for an energy storage device, the capacitance, that is, the specific capacitance, is 200 F/g or more at a specific current of 1.0 A/g, preferably 300 F/g or more, more preferably 400 F/g or more, a significant increase effect of specific capacity can be obtained, preferably 400 F/g or more, more preferably 450 F/g or more. can be obtained

Hereinafter, the present invention will be described in more detail based on Examples and Comparative Examples. However, the following examples and comparative examples are only examples for explaining the present invention in more detail, and the scope of the present invention is not reduced or limited by the following examples and comparative examples.

Preparation Example 1

3,4'-diaminodiphenyl ether (3,4'-Diaminodiphenyl Ether) was mixed with terephthalic acid and isophthalic acid in a molar ratio of 1:1 to prepare a mixture. The molar ratio of terephthalic acid and isophthalic acid was 60:40.

Triphenyl phosphate (Triphenyl Phosphite) and pyridine (Pyridine) were added to the mixture, and N-methylpyrrolidone (N-Methylpyrrolidone) solvent was added to dissolve. Polyetheramide-based polymer was synthesized by solution polymerization of the mixed solution at 100° C. for 16 hours. Inherent viscosity (θ _inh ) related to the molecular weight of the synthesized polyetheramide-based polymer was analyzed as a solution viscosity using an Ubbelohde viscometer, and the result was 0.97 dl/g.

Preparation 2

A mixture was prepared by mixing 3,4'-diaminodiphenyl ether (3,4'-Diaminodiphenyl Ether) with terephthalic acid in a 1:1 molar ratio.

Triphenyl phosphate (Triphenyl Phosphite) and pyridine (Pyridine) were added to the mixture, and N-methylpyrrolidone (N-Methylpyrrolidone) solvent was added to dissolve. Polyetheramide-based polymer was synthesized by solution polymerization of the mixed solution at 100° C. for 16 hours. Inherent viscosity (θ _inh ) related to the molecular weight of the synthesized polyetheramide-based polymer was analyzed as a solution viscosity using an Ubbelohde viscometer, and the result was 0.71 dl/g.

Preparation 3

3,4'-diaminodiphenyl ether (3,4'-Diaminodiphenyl Ether) was mixed with isophthalic acid in a molar ratio of 1:1 to prepare a mixture.

Triphenyl phosphate (Triphenyl Phosphite) and pyridine (Pyridine) were added to the mixture, and N-methylpyrrolidone (N-Methylpyrrolidone) solvent was added to dissolve. Polyetheramide-based polymer was synthesized by solution polymerization of the mixed solution at 100° C. for 16 hours. Inherent viscosity (θ _inh ) related to the molecular weight of the synthesized polyetheramide-based polymer was analyzed as a solution viscosity using an Ubbelohde viscometer, and the result was 0.48 dl/g.

[Example 1]

With respect to the total weight of the spinning solution, the polyetheramide-based polymer prepared in Preparation Example 1 and polyvinylpyrrolidone were in a ratio of 70:30 by weight, and the solid content was 15% by weight. N-methylpyrrolidone was used as the solvent of the spinning solution, and after mixing with the solid content and the solvent, the spinning solution was stirred at 30° C. for 12 hours to prepare a spinning solution for electrospinning. The prepared spinning solution was put into a syringe needle having a gauge of 21 and electrospun using it as an electrospinning device.

The voltage was 15 kV, the distance between the electrospinning hole and the collecting plate was fixed at 25 cm, and the electrospinning speed was adjusted at a flow rate of 0.5 ml/hr to prepare a polyetheramide-based nanofiber precursor. After drying the prepared polyetheramide-based nanofiber precursor at 80°C for 24 hours in a vacuum oven, it was put into a carbonization furnace and vacuum was applied while maintaining it at 30°C to remove air and moisture, and then with argon gas. After creating atmospheric conditions, the temperature was raised at a rate of 10 °C/min, carbonization was performed at 1000 °C, and carbon nanofibers were prepared, and the physical properties were analyzed as follows.

Morphological structural analysis

The carbon nanofibers and polyetheramide-based nanofiber precursors were observed with a scanning electron microscope (SEM). Referring to a) and b) of FIG. 1, it was observed that the average diameter of the polyetheramide-based nanofiber precursor was 1.88 νm, and the average diameter of carbon nanofibers was 1.43 νm, and in the case of carbon nanofibers, the polyetheramide-based nanofiber precursor was polyether amide-based by the carbonization process. Although the fiber diameter was slightly reduced compared to the etheramide-based nanofiber precursor, it was confirmed that the fiber structure was maintained.

Raman Spectroscopy analysis

Looking at the Raman spectrum results of carbon nanofibers by Raman Spectroscopy analysis in FIG. 2, the G-band (1581cm ^-1 ) and D-band (1365cm ^-1 ) peaks observed in the graphite structure are generated. It was confirmed that carbonization and graphitization were performed, and a band similar to that of conventional carbon nanofibers could be observed.

Energy Dispersive X-ray Spectroscopy analysis

Energy dispersive spectroscopy was performed to analyze the oxygen (O), nitrogen (N), and carbon (C) component ratios of carbon nanofibers and polyetheramide-based nanofiber precursors. The energy dispersive spectroscopy curve can be confirmed in FIG. 3, and the component ratio analysis results are shown in Table 1 below.

Carbon (atomic %) Nitrogen (atomic %) Oxygen (atomic %) Polyetheramide polymer based
nanofiber precursor 71.72 11.27 17.01 Polyetheramide polymer-based carbon nanofibers 89.29 5.50 5.21

From the above results, it was confirmed that carbon nanofibers had a carbonization process added when compared to polyetheramide-based nanofiber precursors, and the nitrogen atom and oxygen atom content decreased after carbonization, but were doped with 5.5 atom% nitrogen.

Cyclic voltammogram analysis

A cyclic voltammetry test was performed to evaluate the electrochemical properties of the carbon nanofibers prepared above as an energy storage device and their performance as an electrode material. For the measurement, the prepared carbon nanofiber was cut to 1 mg weight and used as a working electrode, platinum was used as a counter electrode, and a saturated calomel electrode was used as a reference electrode. was used as The electrolyte solution for electrochemical analysis was prepared by putting potassium hydroxide in water at a 6 molar concentration and stirring at 30° C. for about 2 hours.

4 is a graph showing a cyclic voltammogram. It can be observed that the generated current peak is seen at -20 to 10 mA, the graph shows symmetry, and the behavior of the electric double layer is dominant. It can be seen that the cyclic voltammogram area is wider than in the case of using a conventional graphite electrode, and has a slight oxidation-reduction peak and high current density due to nitrogen doping.

Charge and discharge test results

In order to evaluate the performance of the prepared carbon nanofiber as an electrode material for an energy storage device, it was cut to a weight of 1 mg and used as a working electrode, and was charged and discharged at a specific current in the range of 1 to 10 A/g. An experiment was conducted.

5 is a graph showing the change in voltage according to the charging and discharging times, and as can be seen in FIG. 5, when the carbon nanofiber electrode of the present invention is adopted, the charging and discharging efficiency is higher than when an electrode made of a conventional graphite material is used. It was confirmed that it significantly increased, indicating a long charging and discharging time, and it was confirmed that the symmetrical electric double layer behavior was dominant.

Analysis of capacitance (specific capacitance)

In order to evaluate the performance of the prepared carbon nanofiber as an electrode material for an energy storage device, the carbon nanofiber prepared in Example 1 was cut to a weight of 1 mg and used as a working electrode, 1 to 10 A The capacitance (capacitance) was measured at a specific current in the range of /g. At this time, the capacitance was measured based on the results of the charging and discharging experiments.

6 , the capacitance at a specific current of 1 A/g was measured to be 459.8 F/g, and it was confirmed that the capacitance at a specific current of 10 A/g was 194.1 F/g, indicating a high capacitance.

In view of the fact that it has been reported to have a capacitance of 150 to 250 F/g at a specific current of 1 A/g when an electrode made of a conventional graphite material is used, the discharge (capacity) effect is about twice or more It can be seen that, compared to graphite artificially doped with nitrogen, it has very excellent performance.

Power and energy density test results

In order to evaluate the performance of the prepared carbon nanofiber as an electrode material for an energy storage device, the carbon nanofiber prepared in Example 1 was cut to a weight of 1 mg and used as a working electrode, and charging and discharging experiments were conducted. Based on the results, power and energy density were measured.

In FIG. 7 , when the power density is 1000 (W/kg), a high energy density of 127.7 (Wh/kg) is shown, and the energy density is superior to that of the conventional carbon nanofiber-based electrode materials. This can be said to compensate for the low energy density, which is a disadvantage of capacitors among energy storage devices.

[Example 2]

In Example 1, when preparing the polyetheramide-based nanofiber precursor, an electrospinning solution was prepared in a ratio of polyetheramide-based polymer and polyvinylpyrrolidone of 60:40 to prepare carbon nanofibers. Carbon nanofibers were prepared using the same material and method as in Example 1.

The specific capacity, power density and energy density of the carbon nanofibers are shown in Table 2 below.

[Example 3]

In Example 1, when preparing the polyetheramide-based nanofiber precursor, an electrospinning solution was prepared at a ratio of polyetheramide-based polymer and polyvinylpyrrolidone of 80:20 to prepare carbon nanofibers. Carbon nanofibers were prepared using the same material and method as in Example 1.

The specific capacity, power density and energy density of the carbon nanofibers are shown in Table 2 below.

[Example 4]

When preparing the polyetheramide-based nanofiber precursor in Example 1, the same materials as in Example 1 and Carbon nanofibers were prepared by this method. As a result, it was confirmed that the capacitance, energy density, and power density were somewhat lower than those of Example 1, and are shown in Table 2 below.

[Example 5]

In Example 1, carbon nanofibers were manufactured using the same materials and methods as in Example 1, except that the polyetheramide-based polymer of Preparation Example 2 was used instead of the polyetheramide-based polymer of Preparation Example 1. As a result, it was confirmed that the capacitance, energy density, and power density were somewhat lower than those of Example 1, and are shown in Table 2 below.

[Example 6]

In Example 1, carbon nanofibers were manufactured using the same materials and methods as in Example 1, except that the polyetheramide-based polymer of Preparation Example 3 was used instead of the polyetheramide-based polymer of Preparation Example 1. As a result, it was confirmed that the capacitance, energy density, and power density were somewhat lower than those of Example 1, and are shown in Table 2 below.

specific capacity
(F/g, specific current: 1 A/g) power density
(W/kg) energy density
(Wh/kg) Example 1 459.8 1000 127.7 Example 2 419.2 1000 116.4 Example 3 293.0 1000 97.7 Example 4 270.0 1000 95.0 Example 5 240.0 1000 93.5 Example 6 225.0 1000 91.0

Nitrogen-doped carbon nanofibers manufactured according to the method for producing carbon nanofibers presented in the present invention exhibit excellent electrochemical properties with excellent durability and stability, as evidenced by the results of the above experimental examples, such as capacitors, secondary batteries, mobile devices, etc. It can be applied as an electrode material and activated carbon of an energy storage device in various fields, and the present invention is not limited to these specific examples.

Although the preferred embodiment of the present invention has been described above, the present invention can use various changes, modifications, and equivalents, and the present invention can use the same by appropriately modifying the above embodiment.

It is clear that it can be applied to Accordingly, the above description is not intended to limit the scope of the present invention, which is defined by the limits of the following claims.

Claims (13)

a) preparing a polyetheramide-based nanofiber precursor by electrospinning a spinning solution containing a polyetheramide-based polymer and a solvent; and
b) carbonizing the polyetheramide-based nanofiber precursor to prepare nitrogen-doped carbon nanofibers. The method of claim 1,
The polyetheramide-based polymer of step a) includes repeating units represented by the following Chemical Formulas 1 and 2, and the polyetheramide-based polymer is a block copolymer or a random copolymer. Method for producing carbon nanofibers.
[Formula 1]

[Formula 2]

The method of claim 1,
The spinning solution is a method for producing carbon nanofibers in which a porosity forming agent and a polyetheramide-based polymer are mixed. 4. The method of claim 3,
The method for producing carbon nanofibers, wherein the porosity forming agent is at least one selected from an acrylic copolymer and a water-soluble polymer. 4. The method of claim 3,
The method for producing carbon nanofibers, wherein the polyetheramide-based polymer and the porosity forming agent are mixed in a weight ratio of 0.3 to 1.0: 0.7 to 0.0. The method of claim 1,
The solvent is N-methyl-2-pyrrolidone, dimethylacetamide, dimethylformamide, dimethylsulfoxide, ethanol, acetone, tetrahydrofuran, isopropanol, formic acid, chloroform, benzene, phenol, carbon tetrachloride, cresol, water, sulfuric acid. , a method for producing carbon nanofibers, which is at least one selected from the group consisting of hydrochloric acid and nitric acid. The method of claim 1,
The electrospinning method for producing carbon nanofibers is performed at a voltage of 1 to 1000 kV and a flow rate of 0.01 to 1000 ml/h. The method of claim 1,
The carbonization of step b) is a method for producing carbon nanofibers that is carried out at a temperature of 500 to 2500 ℃. A carbon nanofiber produced by the method for producing the carbon nanofiber of any one of claims 1 to 8. 10. The method of claim 9,
The carbon nanofiber is a carbon nanofiber containing 0.1 to 10.0 atomic% of nitrogen. 10. The method of claim 9,
The carbon nanofiber has a specific capacity of 50 to 500 F/g, an energy density of 1 to 900 Wh/kg, and a power density of 100 to 50000 W/kg. An electrode material for an energy storage device that is made of the carbon nanofibers of claim 9. 13. The method of claim 12,
The energy storage device is an electric double layer capacitor, a hybrid capacitor, a lithium secondary battery, a solar cell, and a fuel cell electrode material for an energy storage device.

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