KR102270773B1 - Method for improving charge-discharge characteristics of mxene and cnt based energy repositors - Google Patents

Abstract

The present invention relates to a method for improving characteristics of a charging/discharging speed of an energy storage device based on MXene and carbon nanotubes, which is to improve characteristics of a charging/discharging speed of an energy storage device by increasing a specific surface area. To this end, the method comprises the steps of: (a) preparing an MXene solution; (b) preparing a carbon nanotube solution; (c) forming a mixed solution by mixing the MXene solution and the carbon nanotube solution; (d) decompressing and filtering the mixed solution to form a composite film; (e) drying the composite film; and (f) thermally treating the dried composite film.

Description

Method for improving the charging/discharging speed characteristics of maxine and carbon nanotube-based energy storage devices {METHOD FOR IMPROVING CHARGE-DISCHARGE CHARACTERISTICS OF MXENE AND CNT BASED ENERGY REPOSITORS}

The present invention relates to a method for improving the charge/discharge rate characteristics of a maxine and a carbon nanotube-based energy storage device, and more particularly, a maxine and a carbon nanotube-based energy storage for improving the charge/discharge rate characteristic of an energy storage member by increasing a specific surface area It relates to a method for improving the charging/discharging speed characteristics of a ruler.

As one of the two-dimensional materials, the MAX phase (where M is a transition metal, A is a group 13 or 14 element, and X is carbon and/or nitrogen) contains MX with quasi-ceramic properties and a metal element A different from M It has excellent physical properties such as electrical conductivity, oxidation resistance, and machinability as a combined crystalline substance. It is known that more than 60 types of MAX phases have been synthesized so far.

The MAX phase is a two-dimensional material, but unlike graphite or metal dichalcogenide materials, transition metal carbides are stacked between each other's layers by a weak chemical bond between element A and transition metal M. Therefore, it is difficult to transform it into a two-dimensional structure using a general mechanical peeling method or a chemical peeling method.

However, in 2011, a research team led by Professor Michel W. Barsoum of Drexel University selectively removed the aluminum layer using hydrofluoric acid from three-dimensional titanium-aluminum carbide, the MAX phase, to create a two-dimensional structure with completely different properties. transformation was successful. The researchers named the two-dimensional material obtained by exfoliating the MAX phase "MXene". MXene has similar electrical conductivity and strength to that of graphene, and can be applied to various application technologies ranging from energy storage devices to biomedical applications and composites.

However, when the maxine is dispersed in water to prepare a maxine solution, and heat-treated by forming a maxine film in the form of a film, there is a problem in that the specific surface area is reduced.

When the specific surface area is reduced in this way, the specific storage capacity may be lowered, and thus the charge/discharge rate characteristics of the energy storage device may be lowered.

Therefore, there is a need for a technique for improving the charge/discharge rate characteristics of the energy storage device.

Korean Patent Publication No. 10-2017-0036507 (2017.04.03.)

An object of the present invention to solve the above problems is to provide a method for improving the charge/discharge rate characteristics of a maxine and a carbon nanotube-based energy storage element for improving the charge/discharge rate characteristics of the energy storage element by increasing the specific surface area.

The technical problems to be achieved by the present invention are not limited to the technical problems mentioned above, and other technical problems not mentioned can be clearly understood by those of ordinary skill in the art to which the present invention belongs from the description below. There will be.

The configuration of the present invention for achieving the above object is a) preparing a maxin solution; b) preparing a carbon nanotube solution; c) forming a mixed solution by mixing the maxin solution and the carbon nanotube solution; d) filtering the mixed solution under reduced pressure to form a composite film; e) drying the composite film; And f) provides a method for improving the charging and discharging rate characteristics of the maxine and carbon nanotube-based energy storage device, characterized in that it comprises the step of heat-treating the dried composite film.

In an embodiment of the present invention, in step a), the maxin solution is formed by mixing water and maxin, and the concentration of maxin may be 4.9 mg/ml to 5.1 mg/ml.

In an embodiment of the present invention, in step b), the carbon nanotube solution is formed by mixing ethanol and carbon nanotubes, and the concentration of the carbon nanotubes is 0.4 mg/ml to 0.6 mg/ml can be characterized.

In an embodiment of the present invention, in step b), the carbon nanotube solution is formed by mixing the ethanol and the carbon nanotube with an amp 60% condition by a tip sonicator for 1 hour can be done with

In an embodiment of the present invention, in step c), the mixed solution may be prepared by mixing the maxin solution and the carbon nanotube solution in a ratio of 8:2.

In an embodiment of the present invention, in step e), the composite film may be dried in a desiccator.

In an embodiment of the present invention, in step f), the composite film may be heat-treated at a temperature of 800°C to 1,000°C for a time of 20 minutes to 40 minutes.

In an embodiment of the present invention, the maxin solution is Ti ₂ C, Ti ₃ C ₂ , V ₂ C, Nb ₂ C, (Ti _0.5 , Nb _0.5 ) ₂ CT _x , Ti ₃ CN, (V _0.5 , Cr _0.5 ) ₃ C ₂ , Ta ₄ C ₃ and Nb ₄ C ₃ can do.

In an embodiment of the present invention, the maxin solution may be characterized in that it is composed of a chemical formula _{of M n} + ₁ X _n.

In an embodiment of the present invention, M in the formula of M _n + ₁ X _{n may be a leading transition metal.}

In an embodiment of the present invention _{, X in the formula of M n} + ₁ X _n may include at least one of carbon and nitrogen.

According to the effect of the present invention according to the above configuration, the specific surface area of the composite film can be improved, thereby improving the charge/discharge characteristics of the energy storage element.

It should be understood that the effects of the present invention are not limited to the above-described effects, and include all effects that can be inferred from the configuration of the invention described in the detailed description or claims of the present invention.

1 is a flowchart of a method for improving the charging/discharging rate characteristics of a maxine and a carbon nanotube-based energy storage device according to an embodiment of the present invention.
Figure 2 is a BET specific surface area according to the relative pressure of NM (non-annealing MXene), NMC (non-annealing MXene / CNT nanocomposite), HM (high temp. annealing MXene), HMC (high temp. annealing MXene / CNT nanocomposite) is a graph showing
3 is a graph showing the pore volume per unit mass for the pore diameters of NM, NMC, HM, and HMC.
4 is an HR-SEM image of NMC.
5 is an HR-SEM image of an HMC according to an embodiment of the present invention.
6 is an HR-SEM image of NM.
7 is an HR-SEM image of HM.
8 is a graph showing the non-accumulated capacity according to the scan rates of NM and HM.
9 is a graph showing the current density according to the voltage for each scan rate of NM and HM.
10 is a graph showing measurement results using electrochemical impedance spectroscopy for NM and HM.
11 is a graph showing the non-accumulated capacity according to the scan speed of the NMC and the HMC.
12 is a graph showing the current density according to the voltage for each scan rate of the NMC and the HMC.
13 is a graph showing measurement results using electrochemical impedance spectroscopy for NMC and HMC.
14 is a graph showing the non-accumulated capacity according to the scan rates of NM, NMC, HM, and HMC.
15 is a graph showing the current density according to voltage for each scan rate of NM, NMC, HM, and HMC.
16 is a graph showing measurement results using electrochemical impedance spectroscopy for NM, NMC, HM, and HMC.
17 is a graph showing the current density according to the voltage for each scan rate of the NM.
18 is a graph showing the current density according to the voltage for each scan rate of the HM.
19 is a graph showing the current density according to the voltage for each scan rate of the NMC.
20 is a graph showing the current density according to the voltage for each scan rate of the HMC.
21 is a table showing electrochemical properties for each scan speed according to the prior art and the example.
22 is an HR-SEM image of a non-annealing CNT nanocomposite (NC).
23 is a HR-SEM image of HC (high temp. annealing CNT nanocomposite).

Hereinafter, the present invention will be described with reference to the accompanying drawings. However, the present invention may be embodied in several different forms, and thus is not limited to the embodiments described herein. And in order to clearly explain the present invention in the drawings, parts irrelevant to the description are omitted, and similar reference numerals are attached to similar parts throughout the specification.

Throughout the specification, when a part is said to be “connected (connected, contacted, coupled)” with another part, it is not only “directly connected” but also “indirectly connected” with another member interposed therebetween. "Including cases where In addition, when a part "includes" a certain component, this means that other components may be further provided without excluding other components unless otherwise stated.

The terms used herein are used only to describe specific embodiments, and are not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly dictates otherwise. In this specification, terms such as "comprises" or "have" are intended to designate that the features, numbers, steps, operations, components, parts, or combinations thereof described in the specification exist, but one or more other features It should be understood that this does not preclude the existence or addition of numbers, steps, operations, components, parts, or combinations thereof.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a flowchart of a method for improving the charging/discharging rate characteristics of a maxine and a carbon nanotube-based energy storage device according to an embodiment of the present invention.

As shown in FIG. 1 , in the method of improving the charge/discharge rate characteristics of maxine and carbon nanotube-based energy storage device, first, a step (S10) of preparing a maxine solution may be performed.

In the step of preparing a maxin solution (S10), the maxin solution is Ti ₂ C, Ti ₃ C ₂ , V ₂ C, Nb ₂ C, (Ti _0.5 , Nb _0.5 ) ₂ CT _x , Ti ₃ CN, (V _0.5 , Cr _0.5 ) ₃ C ₂ , Ta ₄ C ₃ and Nb ₄ C ₃ may be one of .

In addition, the Maxine solution in the formula of which can be made by the chemical formula of M _n + ₁ X _n, wherein M _n + ₁ X _n M can be a metal leading edge. And. In the _{formula of M n} + ₁ X _n , X may include at least one of carbon and nitrogen.

The maxin solution prepared in this way is a two-dimensional layered structure, in which layers composed of atoms are stacked to form a multi-layered structure. The maxine solution, which is a two-dimensional multilayer structure, is light and has a low density, has excellent electrical conductivity, and can be easily separated from each other, so that it can be used as a radio wave absorber in various fields.

In the step of preparing a maxin solution (S10), the maxin solution is formed by mixing water and maxine, and the concentration of maxin may be 4.9 mg/ml to 5.1 mg/ml.

After the step of preparing the maxin solution (S10), the step of preparing the carbon nanotube solution (S20) may be performed.

In the step of preparing the carbon nanotube solution (S20), the carbon nanotube solution is formed by mixing ethanol and carbon nanotube, and the concentration of the carbon nanotube may be 0.4 mg/ml to 0.6 mg/ml. .

In the step of preparing the carbon nanotube solution (S20), the carbon nanotube solution may be formed by mixing the ethanol and the carbon nanotube with an amp 60% condition by a tip sonicator for 1 hour. .

After the step of preparing the carbon nanotube solution (S20), the maxin solution and the carbon nanotube solution are mixed to form a mixed solution (S30).

In the step (S30) of mixing the maxine solution and the carbon nanotube solution to form a mixed solution, the mixed solution may be prepared by mixing the maxine solution and the carbon nanotube solution in a ratio of 8:2.

After the step (S30) of mixing the maxine solution and the carbon nanotube solution to form a mixed solution, the step (S40) of forming a composite film by filtering the mixed solution under reduced pressure may be performed.

More specifically, the prepared mixed solution is prepared in the form of a film through spin coating, drop cast, and vacuum filtration to prepare a composite film, and spin coating as described above, By manufacturing the composite film through various methods such as drop casting and vacuum filtration, it is possible to effectively produce a composite film according to manufacturing conditions or conditions.

After the step (S40) of forming a composite film by filtering the mixed solution under reduced pressure, a step (S50) of drying the composite film may be performed.

In the step of drying the composite film (S50), the composite film may be dried in a desiccator.

After the step (S50) of drying the composite film, a step (S60) of heat-treating the dried composite film may be performed.

In the step of heat-treating the dried composite film (S60), the composite film may be provided to be heat-treated at a temperature of 800 °C to 1,000 °C for a time of 20 minutes to 40 minutes.

When the heat treatment is performed at a temperature of less than 800° C. or for a time of less than 20 minutes, the specific surface area is not sufficiently increased and the specific storage capacity is lowered. When annealing at a temperature of more than 1000° C. or for a time exceeding 40 minutes, the working time is increased, characteristics may be reduced.

Preferably, the composite film may be prepared to be heat treated at 900° C. for 30 minutes.

After the heat treatment of the dried composite film (S60), the heat-treated composite film may be punched to have a predetermined diameter to prepare an electrode for an energy storage device.

Figure 2 is a BET specific surface area according to the relative pressure of NM (non-annealing MXene), NMC (non-annealing MXene / CNT nanocomposite), HM (high temp. annealing MXene), HMC (high temp. annealing MXene / CNT nanocomposite) is a graph showing

As shown in FIG. 2, when NM and NMC are compared, the specific surface area of MXene/CNT is larger than that of Maxine. This is because carbon nanotubes act as a spacer between MXene sheets, thereby increasing the interlayer spacing of maxine and increasing the specific surface area.

In addition, comparing NM and HM, it can be seen that the specific surface area of the maxine film is rather reduced when heat-treated. This is due to a decrease in specific surface area due to re-stacking of maxine sheets after heat treatment.

And, comparing NMC and HMC, in the case of MXene/CNT, it can be confirmed that the specific surface area increases when heat-treated. This is because carbon nanotubes are inserted as spacers between the maxine sheets, preventing re-stacking of the maxine sheets even after heat treatment.

That is, it can be confirmed that the specific surface area is decreased when maxine is heat treated, but the specific surface area is rather increased during heat treatment of the composite formed by mixing maxine and carbon nanotubes.

3 is a graph showing the pore volume per unit mass for the pore diameters of NM, NMC, HM, and HMC.

Figure 3 (b) is an enlarged graph when the pore diameter is 0 to 20 in Figure 3 (a).

Referring to FIG. 3 , when comparing NM and NMC, it can be seen that the carbon nanotube acts as a spacer, thereby increasing the pore volume per unit mass. That is, the porosity is improved.

In addition, comparing NM and HM, it can be seen that after heat treatment, the maxine sheet was re-stacked to reduce the pore volume per unit mass.

Comparing NMC and HMC, since carbon nanotubes are inserted as spacers between maxine sheets, it prevents re-stacking of maxine sheets even after heat treatment. Accordingly, it can be seen that the pore volume per unit mass increases and the size of the pore diameter is variously distributed.

As shown in FIGS. 2 and 3 , in the HMC according to an embodiment of the present invention, the specific surface area and the pore volume per unit mass increase during heat treatment, and the electrochemical performance is improved as the size of the pore diameter is variously distributed. can

Specifically, the physical adsorption/desorption mechanism of the ions provides a path through which the electrolyte ions of the supercapacitor can move rapidly, and can increase the active sites for the adsorption/desorption of the electrolyte ions. That is, it is possible to have fast charging/discharging and excellent output characteristics.

4 is an HR-SEM image of an NMC, and FIG. 5 is an HR-SEM image of an HMC according to an embodiment of the present invention.

Comparing FIGS. 4 and 5 , it can be seen that the wrinkle of the maxine surface is increased in HMC after heat treatment than in NMC before heat treatment.

This means an increase in specific surface area and pores, and thus the above-described electrochemical performance can be improved.

6 is an HR-SEM image of NM, and FIG. 7 is an HR-SEM image of HM.

6 and 7, the maxine surface change is not clearly observed in the NM before the heat treatment and the HM after the heat treatment.

That is, when maxine alone is used without carbon nanotubes, the effect of improving electrochemical performance before and after heat treatment of the maxine film cannot be expected.

8 is a graph showing the specific storage capacity according to the scan rates of NM and HM, FIG. 9 is a graph showing the current density according to the voltage according to the scan rates of NM and HM, and FIG. 10 is the electrochemical impedance of the NM and HM It is a graph showing the measurement result using the spectroscopy method.

Referring to FIGS. 8 to 10 , NM shows excellent performance of 141.1 F/g of non-accumulating capacity at the initial speed of 10 mV/s, but shows significant performance degradation as the speed increases. In addition, there is a problem in that the reserve capacity is 3.1 F/g at the very fast 2 V/s, maintaining only 2.2% of the initial performance.

And, after heat treatment, the specific storage capacity of HM is greatly reduced from 141.1 F/g to 9.3 F/g at the initial 10 mV/s rate. However, in HM, the rate capability is increased from 2.2% to 33.7% (2 V/s) at the very fast 2 V/s rate, and Rct is reduced from 13.3 Ω to 0.5 Ω. It's hard to say.

11 is a graph showing the specific storage capacity according to the scan rates of NMC and HMC, FIG. 12 is a graph showing the current density according to the voltage according to the scan rates of the NMC and HMC, and FIG. 13 is the electrochemical impedance of the NMC and HMC It is a graph showing the measurement result using the spectroscopy method.

Comparing NMC and HMC with reference to FIGS. 11 to 13 , after heat treatment, the specific storage capacity at the initial 10 mV/s rate is 118.2 F/g and 123.5 F/g, showing similar performance. In addition, rate capability was greatly improved from 20.9% to 72.2% at a very fast 2 V/s speed.

14 is a graph showing the storage capacity according to the scan rates of NM, NMC, HM, and HMC, FIG. 15 is a graph showing the current density according to the voltage according to the scan rates of NM, NMC, HM, and HMC, FIG. 16 is It is a graph showing the measurement results using electrochemical impedance spectroscopy for NM, NMC, HM, and HMC.

14 to 16 , when comparing NM and NMC, it can be seen that the rate capability is improved from 2.2% to 19.8% after carbon nanotubes are added.

And, comparing HM and HMC, it can be seen that the reserve capacity is greatly improved from 9.3 F/g to 123.5 F/g at the initial 10 mV/s.

Through this, it can be seen that after heat treatment, the maxine's non-accumulating capacity is significantly reduced due to the reduction of the active area for adsorption/desorption of ions due to the re-stacking between the maxine sheets.

On the other hand, after heat treatment, MXene/CNT prevents the reduction of the non-accumulating capacity by preventing the carbon nanotubes from being re-stacked between maxin sheets and forming a conductive channel as well as a spacer function, and can have fast charge/discharge rate characteristics. .

17 is a graph showing the current density according to the voltage for each scan rate of NM, FIG. 18 is a graph showing the current density according to the voltage for each scan rate of the HM, and FIG. 19 is a graph showing the current density according to the voltage for each scan rate of the NMC is a graph shown, and FIG. 20 is a graph showing the current density according to the voltage for each scan rate of the HMC.

17 to 20 , a difference in electrochemical performance can be confirmed through current density according to voltage for each scan rate.

As shown, it can be seen that HMC has superior electrochemical performance compared to others.

21 is a table showing electrochemical properties for each scan speed according to the prior art and the example.

Referring to FIG. 21 , it can be seen that the embodiment has a small decrease in non-storage capacity and excellent rate capability even when the scan rate is increased compared to other prior art examples.

22 is a HR-SEM image of NC (non-annealing CNT nanocomposite), and FIG. 23 is an HR-SEM image of HC (high temp. annealing CNT nanocomposite).

22 and 23, bright thick branches are observed in NC, but bright spots are observed in HC due to increased surface density. That is, after heat treatment, the carbon nanotubes are aligned. When the carbon nanotubes are aligned in this way, a conductive channel is formed to provide a fast path for electrolyte ions, and accordingly, a fast charge/discharge rate characteristic can be obtained and output characteristics can be improved.

The above description of the present invention is for illustration, and those of ordinary skill in the art to which the present invention pertains can understand that it can be easily modified into other specific forms without changing the technical spirit or essential features of the present invention. will be. Therefore, it should be understood that the embodiments described above are illustrative in all respects and not restrictive. For example, each component described as a single type may be implemented in a dispersed form, and likewise components described as distributed may be implemented in a combined form.

The scope of the present invention is indicated by the following claims, and all changes or modifications derived from the meaning and scope of the claims and their equivalent concepts should be construed as being included in the scope of the present invention.

Claims (11)

a) preparing a maxin solution;
b) preparing a carbon nanotube solution;
c) forming a mixed solution by mixing the maxin solution and the carbon nanotube solution;
d) filtering the mixed solution under reduced pressure to form a composite film;
e) drying the composite film; and
f) comprising the step of heat-treating the dried composite film,
In step f), the heat treatment is provided at a temperature of 800°C to 1,000°C for a time of 20 minutes to 40 minutes so as to increase the pore volume per unit mass based on the pore diameter of the composite film. A method for improving the charging/discharging rate characteristics of maxine and carbon nanotube-based energy storage devices.
The method of claim 1,
In step a),
The maxin solution is
It is formed by mixing water and maxine, and the maxine concentration is 4.9 mg/ml to 5.1 mg/ml.
The method of claim 1,
In step b),
The carbon nanotube solution,
It is formed by mixing ethanol and carbon nanotubes, and the concentration of the carbon nanotubes is 0.4 mg/ml to 0.6 mg/ml. A method for improving charge/discharge rate characteristics of maxine and carbon nanotube-based energy storage devices.
4. The method of claim 3,
In step b),
The carbon nanotube solution,
The method for improving the charging/discharging rate characteristics of maxine and carbon nanotube-based energy storage device, characterized in that the ethanol and the carbon nanotube are mixed for 1 hour at an amp condition of 60% by an ultrasonic dispersing device (tip sonicator).
The method of claim 1,
In step c),
The mixed solution is
A method for improving charge/discharge rate characteristics of a maxine and carbon nanotube-based energy storage device, characterized in that it was prepared by mixing the maxine solution and the carbon nanotube solution in a ratio of 8:2.
The method of claim 1,
In step e),
The method for improving the charge-discharge rate characteristics of the maxine and carbon nanotube-based energy storage device, characterized in that the composite film is dried in a desiccator.
delete The method of claim 1,
The maxin solution is Ti ₂ C, Ti ₃ C ₂ , V ₂ C, Nb ₂ C, (Ti _0.5 , Nb _0.5 ) ₂ CT _x , Ti ₃ CN, (V _0.5 , Cr _0.5 ) ₃ C ₂ , Ta ₄ C ₃ and Nb ₄ C ₃ A method for improving the charging/discharging rate characteristics of maxine and carbon nanotube-based energy storage devices.
9. The method of claim 8,
The maxine solution is a method of improving the charge/discharge rate characteristics of a maxine and a carbon nanotube-based energy storage device, characterized in that it consists of a chemical formula _{of M n} + ₁ X _n.
10. The method of claim 9,
The M _n + ₁ X _{n in} the formula of M is a leading transition metal maxine and carbon nanotube-based energy storage device charging/discharging rate characteristics improvement method, characterized in that.
The method of claim 1,
In the _{formula of M n} + ₁ X _n , X is a method for improving charge/discharge rate characteristics of maxine and carbon nanotube-based energy storage devices, characterized in that it includes at least one of carbon and nitrogen.

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