KR102078303B1 - Method of preparing nitrogen atom doped carbon felt for use in vanadium redox flow battery - Google Patents

Abstract

Disclosed are a manufacturing method of carbon felts having nitrogen atoms doped thereon, carbon felts manufactured thereby, and a vanadium redox flow battery comprising the same. The manufacturing method comprises the steps of: supporting a carbon felt comprising carbon fibers in a surface treating solution containing monomers having nitrogen atoms, irradiating ultrasonic waves, coating polymers having the monomer polymerized on part or the entire of the carbon fibers and thus, manufacturing a carbon felt containing carbon fibers having the polymers coated thereon; and thermally treating the carbon felt containing the polymers coated thereon and thus, manufacturing a carbon felt containing carbon fibers having nitrogen atoms doped thereon. The manufacturing method has a short surface treating time, is highly likely to be industrially used with a large-scale process and enables uniform surface treatments. In addition, a vanadium redox flow battery containing the carbon felt having nitrogen atoms doped thereon causes reversibly an oxidation-reduction reaction of vanadium through a surface treatment to increase an energy efficiency.

Description

METHODS OF PREPARING NITROGEN ATOM DOPED CARBON FELT FOR USE IN VANADIUM REDOX FLOW BATTERY}

The present invention relates to a method for preparing a carbon felt doped with nitrogen atoms, a carbon felt prepared according to the present invention, and a vanadium redox flow battery comprising the same. Forming and coating the carbon felt with the polymer and then heat treatment to produce a carbon felt doped with a nitrogen atom, and a carbon felt and a vanadium redox flow battery comprising the same.

In general, the redox flow battery is attracting attention as an electric energy storage system that has a long lifespan, is safe, and has an independent design of output and capacity, which facilitates mass storage. In particular, since the vanadium redox flow battery uses vanadium ions in the positive / cathode electrolyte as the same active material, there is no contamination problem caused by ion-crossover, which is a problem in other types of redox flow batteries, and thus shows high battery efficiency. In the case of the vanadium redox flow battery, the oxidation / reduction reaction of the active material occurs only at the electrode surface, so it is considered to be an important part to increase the electrode reactivity.

In particular, electrodes used in vanadium redox flow cells should have a large surface area, high electrical conductivity, a suitable porous structure for electrolyte flow and high vanadium oxidation / reduction activity. However, since redox flow battery uses strong acid electrolyte, electrode material having acid resistance should be used. Therefore, the most suitable carbon felt for these conditions is widely used.

However, since the surface of the carbon felt electrode has low electrochemical activity on the active material, there is a limit in increasing the energy efficiency and discharge capacity of the battery.

In order to solve this problem, heat treatment, acid treatment, oxide coating, carbon-based material coating, nitrogen substitution, and the like have been conducted to give functional groups to the surface of the carbon felt electrode. Heat treatment and acid treatment methods are simple and commercialized by breaking the C-C bond to have a surface functional group, but there is a problem of electrical conductivity and durability due to damage to the surface of the carbon electrode. The method of coating an oxide such as zirconium oxide or manganese oxide in order to use -OH on the ceramic surface has a problem of inferior electrical conductivity. Coating of carbon-based materials such as graphene or CNTs is expensive.

During the surface treatment studies, the nitrogen substitution showed an excellent performance, but the nitrogen substitution method reported so far requires a long time process, or the use of harmful gases such as ammonia gas causes mass production constraints and environmental problems. .

The present invention is to solve the problems of the prior art as described above, an object of the present invention is to provide a short surface treatment time, high commercial availability in a large-area process, of the carbon felt doped with nitrogen atoms through a uniform surface treatment It is to provide a manufacturing method.

In addition, it is an object of the present invention to provide a vanadium redox flow battery having a high energy efficiency by making the redox reaction of vanadium occur reversibly well by surface treatment.

According to an aspect of the present invention, (a) a carbon felt containing carbon fibers in a surface treatment solution containing a monomer having a nitrogen atom and ultrasonically irradiated to polymerize the monomer on part or all of the carbon fibers Coating a polymer to produce a carbon felt comprising the carbon fiber coated with the polymer; And (b) heat-treating the carbon felt including the polymer-coated carbon fiber to produce a carbon felt including the carbon fiber doped with nitrogen atoms. The method for preparing a carbon felt doped with nitrogen atoms is provided. .

In addition, the monomer having the nitrogen atom may be a monomer to self-polymerize.

The monomer may also be dopamine.

In addition, the ultrasonic treatment may be performed at a frequency of 20 to 100kHz.

In addition, the sonication may be performed for 10 to 120 minutes.

In addition, the sonication may be performed for 20 to 40 minutes.

Also in step (a), the polymer formation and the coating can be carried out simultaneously.

In addition, the surface treatment solution may have a concentration of the monomer is 0.1 to 3mM.

In addition, the surface treatment solution may include a solvent and a buffer solution.

In addition, the solvent may include one or more selected from the group consisting of methanol, ethanol, propanol, isopropyl alcohol, tert-butanol, isobutanol, 2-ethyl hexanol and 2-ethoxy ethanol.

In addition, the surface treatment solution may have a pH of 8.0 to 9.0.

Also in step (b), the heat treatment may be carried out in one or more inert gas atmospheres selected from the group consisting of nitrogen, helium, neon, argon, krypton, xenon and radon.

In addition, in step (b), the heat treatment may be performed at 500 to 1,000 ℃.

According to another aspect of the present invention, there is provided a carbon felt doped with a nitrogen atom produced by the production method.

According to another aspect of the invention, there is provided a vanadium redox flow battery comprising a carbon felt doped with the nitrogen atom.

The method for producing a carbon felt doped with nitrogen atoms of the present invention has a short surface treatment time, high commercial availability in a large-area process, and has an effect of allowing uniform surface treatment.

In addition, the vanadium redox flow battery comprising a carbon felt doped with a nitrogen atom according to the present invention has the effect that the redox reaction of vanadium through the surface treatment is reversible well to increase the energy efficiency.

1 is a schematic diagram of a method for producing a carbon felt according to the present invention.
2 is a SEM analysis result of the carbon felt doped with nitrogen atoms according to Examples 1 to 4 and the carbon felt according to Comparative Example 1.
3 is a SEM analysis result of the carbon felt doped with nitrogen atoms according to Example 2, Examples 5 to 7 and the carbon felt according to Comparative Example 1.
4 is a wettability test results of the carbon felt doped with nitrogen atoms according to Examples 1 to 4 and the carbon felt according to Comparative Example 1.
5 shows XPS results of carbon felts doped with nitrogen atoms according to Examples 2 and 4 and carbon felts according to Comparative Example 1. FIG.
6A is a result of Cyclic Voltammetry (CV) analysis of a carbon felt doped with nitrogen atoms according to Examples 1 to 4 and a carbon felt according to Comparative Example 1. FIG.
6B is a graph showing Delta E _p and I _pa / I _pc values according to FIG. 6A.
7A is a result of Cyclic Voltammetry (CV) analysis of carbon felts doped with nitrogen atoms according to Examples 2 and 5 and 7 and carbon felt according to Comparative Example 1. FIG.
FIG. 7B is a graph showing Delta E _p and I _pa / I _pc values according to FIG. 7A.
8A is a charge efficiency result of current density of vanadium redox flow batteries according to device examples 1 to 4 and device comparison example 1;
8b is an energy efficiency result of each of the current density of the vanadium redox flow battery according to device Examples 1 to 4 and Comparative Example 1.
8c is a result of relative energy efficiency values of current density of vanadium redox flow batteries according to device examples 1 to 4 and device comparison example 1;
FIG. 8D is a voltage efficiency result of current density of a vanadium redox flow battery according to device examples 1 to 4 and device comparison example 1. FIG.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention.

However, the following descriptions are not intended to limit the present invention to specific embodiments, and detailed descriptions of well-known technologies related to the present invention will be omitted when it is determined that the present invention may obscure the gist of the present invention. .

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this application, the terms "comprise" or "having" are intended to indicate that there is a feature, number, step, operation, component, or combination thereof described in the specification, and one or more other features or It is to be understood that the present invention does not exclude the possibility of adding or presenting numbers, steps, operations, components, or combinations thereof.

1 is a schematic diagram of a method for producing a carbon felt according to the present invention.

Hereinafter, a method of manufacturing a carbon felt doped with a nitrogen atom of the present invention will be described with reference to FIG. 1.

First, a surface treatment solution containing a monomer having a nitrogen atom Carbon fiber  Containing Carbon felt Supporting  Said by ultrasonic irradiation Carbon fiber  Coating the polymer by polymerizing the monomer on part or all of the polymer Carbon fiber  To prepare a carbon felt comprising (step a).

The monomer having the nitrogen atom may be a monomer that self-polymerizes.

The monomer may be dopamine.

The surface treatment solution may have a concentration of the monomer is 0.1 to 3mM.

The surface treatment solution may include a solvent and a buffer solution.

The solvent may include one or more selected from the group consisting of methanol, ethanol, propanol, isopropyl alcohol, tert-butanol, isobutanol, 2-ethyl hexanol and 2-ethoxy ethanol, preferably methanol It may include.

The surface treatment solution may have a pH of 8.0 to 9.0, preferably 8.5.

The ultrasonic treatment may be performed at a frequency of 20 to 100 kHz.

The ultrasonic treatment may be performed for 10 to 120 minutes, preferably 20 to 40 minutes.

The polymer formation and the coating can be performed simultaneously.

Next, the polymer is coated Carbon fiber  Containing Carbon felt  Heat treatment to prepare a carbon felt comprising a carbon fiber doped with nitrogen atoms (step b).

The heat treatment may be performed in one or more inert gas atmospheres selected from the group consisting of nitrogen, helium, neon, argon, krypton, xenon and radon.

In addition, the heat treatment may be performed under reducing conditions.

The heat treatment may be performed at 500 to 1,000 ° C.

In another aspect, the present invention provides a carbon felt doped with a nitrogen atom prepared by the above production method.

In another aspect, the present invention provides a vanadium redox flow battery comprising a carbon felt doped with the nitrogen atom.

EXAMPLE

Hereinafter, the present invention will be described in more detail with reference to Examples. However, this is for illustrative purposes and the scope of the present invention is not limited thereto.

Example 1 Preparation of Carbon Felt Doped with Nitrogen Atoms

After mixing the weight ratio of methanol and Tris-buffer solution to 50:50, dopamine was added so that the concentration of dopamine was 0.25mM to prepare a surface treatment solution. Polydopamine was prepared by loading carbon felt (trade name: MJNT GF-051CH) purchased from JNTG in Korea into the surface treatment solution and sonicating by 40kHz ultrasonic wave for 40 minutes. Coated carbon felt was prepared. The polydopamine-coated carbon felt was heat-treated at 700 ° C. in a nitrogen atmosphere to prepare a carbon felt doped with nitrogen atoms.

Example 2 Preparation of Carbon Felt Doped with Nitrogen Atoms

A carbon felt doped with nitrogen atoms was prepared in the same manner as in Example 1 except that the concentration of dopamine was 0.50 mM instead of 0.25 mM.

Example 3 Preparation of Carbon Felt Doped with Nitrogen Atoms

A carbon felt doped with nitrogen atoms was prepared in the same manner as in Example 1 except that the concentration of dopamine was 1.00 mM instead of 0.25 mM.

Example 4 Preparation of Carbon Felt Doped with Nitrogen Atoms

A carbon felt doped with nitrogen atoms was prepared in the same manner as in Example 1 except that the concentration of dopamine was 2.00 mM instead of 0.25 mM.

Example 5 Preparation of Carbon Felt Doped with Nitrogen Atoms

A carbon felt doped with nitrogen atoms was prepared in the same manner as in Example 1 except that the concentration of dopamine was 0.50 mM instead of 0.25 mM, and 20 minutes instead of 40 minutes of sonication time.

Example 6 Preparation of Carbon Felt Doped with Nitrogen Atoms

A carbon felt doped with nitrogen atoms was prepared in the same manner as in Example 1 except that the concentration of dopamine was 0.50 mM instead of 0.25 mM, and 60 minutes instead of 40 minutes of sonication time.

Example 7 Preparation of Carbon Felt Doped with Nitrogen Atoms

A carbon felt doped with nitrogen atoms was prepared in the same manner as in Example 1 except that the concentration of dopamine was 0.50 mM instead of 0.25 mM, and 80 minutes instead of 40 minutes for the sonication time.

Comparative Example 1: Preparation of Carbon Felt

Carbon felt (trade name: MJNT GF-051CH) was purchased from JNTG in Korea and used as Comparative Example 1.

Device Example 1 Fabrication of Vanadium Redox Flow Battery

A nitrogen atom-doped carbon felt prepared according to Example 1 was used as an electrode of a vanadium redox flow battery.

An anode cell and a cathode cell were prepared by laminating an end plate, a bipolar plate, a flow path frame, and a carbon felt doped with nitrogen atoms prepared according to Example 1. The anode cell and the cathode cell were fabricated as one cell by laminating the carbon felts facing each other with an ion exchange membrane interposed therebetween. A positive electrode electrolyte tank was connected to one side of the cell using a tube, and a negative electrode electrolyte tank was connected to the other side, and a vanadium redox flow battery was manufactured by allowing the electrolyte to circulate inside the cell using a pump.

Device Example 2 Fabrication of Vanadium Redox Flow Cell

A vanadium redox flow battery was manufactured in the same manner as in Example 1, except that the carbon felt prepared according to Example 2 was used instead of the carbon felt prepared according to Example 1.

Device Example 3: Fabrication of Vanadium Redox Flow Cell

A vanadium redox flow battery was manufactured in the same manner as in Example 1, except that the carbon felt manufactured according to Example 3 was used instead of the carbon felt prepared according to Example 1.

Device Example 4 Fabrication of Vanadium Redox Flow Battery

A vanadium redox flow battery was manufactured in the same manner as in Device Example 1, except that the carbon felt prepared according to Example 4 was used instead of the carbon felt prepared according to Example 1.

Device Comparison Example 1 Fabrication of Vanadium Redox Flow Battery

A vanadium redox flow battery was manufactured in the same manner as in Example 1, except that the carbon felt prepared according to Comparative Example 1 was used instead of the carbon felt prepared according to Example 1.

[Test Example]

Test Example 1: SEM (Scanning Electron Microscope) Analysis by Dopamine Content

2 is a SEM analysis result of the carbon felt doped with nitrogen atoms according to Examples 1 to 4 and the carbon felt according to Comparative Example 1. Referring to FIG. 2, in comparison with Comparative Example 1, in Examples 1 to 3, dopamine was polymerized to confirm that carbon materials including nitrogen atoms adhered to the surface of the carbon felt as dots. In the case of Example 4, it was confirmed that a large amount of dopamine is agglomerated and polymerized.

Test Example 2: SEM Analysis by Sony Time

3 is a SEM analysis result of the carbon felt doped with nitrogen atoms according to Example 2, Examples 5 to 7 and the carbon felt according to Comparative Example 1. Referring to FIG. 3, when the sonication time is longer than 60 minutes, since the temperature of the surface treatment solution is increased by sonication energy, it can be confirmed that the dopamine is aggregated even if the dopamine content is not high.

Test Example 3: Wettability Analysis

4 is a wettability test results of the carbon felt doped with nitrogen atoms according to Examples 1 to 4 and the carbon felt according to Comparative Example 1. Referring to FIG. 4, since Comparative Example 1 is hydrophobic, water droplets formed when distilled water was dropped on the surface, and floated when immersed in a vanadium electrolyte solution. In the case of Examples 1 to 4 was changed to hydrophilic through the surface treatment was not absorbed even when distilled water drops, it was confirmed that the water drops when immersed in the vanadium electrolyte solution.

Test Example 4: X-ray photoelectron spectroscopy (XPS) analysis

5 shows XPS results of carbon felts doped with nitrogen atoms according to Examples 2 and 4 and carbon felts according to Comparative Example 1. FIG. Referring to Figure 5, Comparative Example 1 can be seen that there is no nitrogen atom by the observation of the peak that can be determined that the N peak is noise, Examples 2 and 4 confirmed that the N peak is clearly visible doped with a nitrogen atom on the surface Could.

Test Example 5: Cyclic Voltammetry (CV) Analysis by Dopamine Content

FIG. 6A shows the results of Cyclic Voltammetry (CV) analysis of the carbon felt doped with nitrogen atoms according to Examples 1 to 4 and the carbon felt according to Comparative Example 1, and FIG. 6B illustrates Delta E _p and I _pa / I _pc according to FIG. 6A. A graph showing values.

If the voltage is increased little by little for a certain time, the oxidation peak appears around 1.1V relative to the counter electrode, and if the voltage is removed, the reduction peak appears. The difference in voltage between these two peaks is Delta E _p It is a value, and the narrower the difference, the lower the resistance. Referring to Figure 6b, when the dopamine content is 0.5mM Delta E _p The smallest value was found.

When the current density corresponding to the maximum value at the oxidation peak is I _pa , and the current density corresponding to the minimum value at the reduction peak is I _pc , it can be seen that the closer the I _pa / I _pc value is to 1, the more reversible the reaction is. Referring to FIG. 6B, when the dopamine content was 0.5 mM, it was confirmed that the I _pa / I _pc value was closest to 1.

Test Example 6 Analysis of Cyclic Voltammetry (CV) Over Time by Sonyation

FIG. 7A is a result of Cyclic Voltammetry (CV) analysis of carbon felts doped with nitrogen atoms according to Examples 2 and 5 and 7 and carbon felt according to Comparative Example 1, and FIG. 7B illustrates Delta E _p and I according to FIG. 7A. _A graph showing _pa / I _pc values. Referring to FIG. 7B, when the sonication time is 40 minutes, Delta E _p The smallest value and I _pa / I _pc value was found to be close to 1.

Test Example 7: Charge / discharge test by current density

8A is a charge efficiency result for each current density of vanadium redox flow batteries according to device examples 1 to 4 and device comparison example 1. FIG. Referring to FIG. 8A, the charge efficiency is a value obtained by dividing the discharge capacity of each cycle by the charge capacity, and the charge efficiency is related to the electrical conductivity, so that if the electrical conductivity is good, the electrical conductivity is increased by doping nitrogen atoms to transfer the charge well. Since the charge efficiency is almost the same was confirmed.

8b and 8c show energy efficiency results and relative energy efficiency results according to current densities of vanadium redox flow batteries according to device examples 1 to 4 and device comparison example 1, respectively. 8B and 8C, it was confirmed that the energy efficiency of the vanadium redox flow battery according to Examples 1 to 4 was increased compared to Comparative Example 1. Referring to FIG. 2B, the energy efficiency of Example 1 is slightly higher than that of Comparative Example 1, the energy efficiency of Example 2 is higher than that of Example 1, and the energy efficiency of Example 3 is higher than that of Example 2. Decrease, and the energy efficiency of Example 4 tends to decrease more than Example 3. This is also carried out while the dopamine content in 0.50mM 6b of Example 2 after the dopamine content of the Delta E _p and I _pa / I _pc value showing the lowest point increased to 1.0mM, 2.0mM Delta E _p and I _pa / I value _pc It is similar to this increasing graph.

FIG. 8D is a voltage efficiency result of current density of a vanadium redox flow battery according to device examples 1 to 4 and device comparison example 1. FIG. Referring to FIG. 8D, the voltage efficiency is a value obtained by dividing the energy efficiency by the charge efficiency, showing a tendency similar to that of the energy efficiency graph. This means that the experiment of doping the nitrogen atom of the present invention does not increase the charge efficiency but increases the voltage by decreasing the resistance.

Although preferred embodiments of the present invention have been described above, those of ordinary skill in the art may add, change, delete, or eliminate the elements within the scope not departing from the spirit of the present invention described in the claims. The present invention may be variously modified and changed by addition, etc., which will also be included within the scope of the present invention. For example, each component described as a single type may be implemented in a distributed manner, and similarly, components described as distributed may be implemented in a combined form. The scope of the present invention is shown by the following claims rather than the above description, and all changes or modifications derived from the meaning and scope of the claims and their equivalents should be construed as being included in the scope of the present invention. do.

Claims (15)

(a) Carrying a carbon felt containing carbon fibers in a surface treatment solution containing a dopamine monomer having a nitrogen atom, methanol and a buffer solution and ultrasonically irradiated to polymerize the polymer on the part or all of the carbon fibers Coating to prepare a carbon felt comprising the carbon fiber coated with the polymer; And
(b) heat-treating the carbon felt including the carbon fiber coated with the polymer to produce a carbon felt including the carbon fiber doped with nitrogen atoms;
The sonication is performed at a frequency of 20 to 100 kHz,
The sonication is carried out for 20 to 40 minutes,
The surface treatment solution has a concentration of the monomer is 0.1 to 3mM,
The surface treatment solution is a pH of 8.0 to 9.0 method for producing a carbon atom doped with carbon atoms. The method of claim 1,
A method for producing a carbon felt doped with nitrogen atoms, characterized in that the dopamine monomer having the nitrogen atom self-polymerizes. delete delete delete delete The method of claim 1,
In step (a),
The method for producing carbon felt doped with nitrogen atoms, characterized in that the polymer formation and the coating is performed at the same time. delete delete delete delete The method of claim 1,
In step (b),
The heat treatment is a method for producing a nitrogen atom-doped carbon felt, characterized in that carried out in at least one inert gas atmosphere selected from the group consisting of nitrogen, helium, neon, argon, krypton, xenon and radon. The method of claim 1,
In step (b),
The heat treatment is carried out at 500 to 1,000 ℃ method for producing a carbon felt doped with a nitrogen atom. delete delete

Images