KR101601738B1 - Method for manufacturing graphene nanostructure, graphene nanostructure and energy storage system including the same - Google Patents

Abstract

The method for producing a graphene nanostructure according to the present invention comprises the steps of preparing a first solution by dispersing graphene powder in deionized water, preparing a second solution by dispersing metal oxide in deionized water, 2 solution to form a mixture, adding a nitrogen atom-containing aqueous solution to the mixture, adding an oxidizing agent to the mixture, filtering, washing and drying the mixture, and irradiating the mixture with microwave .

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a graphene nanostructure, a graphene nanostructure, and an energy storage device including the graphene nanostructure,

A graphene nanostructure, and an energy storage device including the graphene nanostructure.

In recent years, there is a growing need for high performance and high capacity of energy storage devices used as power sources for portable devices in connection with the trend toward miniaturization and light weight of portable electronic devices.

The energy storage technology is classified into a battery type that is stored in the form of chemical energy and a non-battery type that is stored and used in the form of physical energy. An example of a battery type is a secondary battery, such as lithium-ion, nickel, or lead-acid battery. The non-battery type is representative of pumped storage and compressed air storage, and is suitable for large-scale storage. However, since there are many natural constraints, the battery type is attracting attention as a leading energy storage technology in the future.

The battery type battery of the energy storage device which is often studied / developed is a device that generates electric power by using a substance capable of electrochemically reacting with the anode and the cathode. A representative example of such a battery is a lithium secondary battery that generates electrical energy by a change in chemical potential when the lithium ions are intercalated / deintercalated in the positive electrode and the negative electrode.

The lithium secondary battery is manufactured by using a material capable of reversible intercalation / deintercalation of lithium ions as a positive electrode and a negative electrode active material, and filling an electrolyte between the positive electrode and the negative electrode.

However, as it is known that the lithium secondary battery is degraded in electrochemical performance due to the expansion of active materials as the charge and discharge are repeated, efforts to find a substance capable of maintaining electrochemical performance even during charging and discharging have been actively carried out It is a situation.

One embodiment of the present invention is to provide a method for producing a graphene nanostructure.

Another embodiment of the present invention is to provide a graphene nanostructure produced by the graphene nanostructure production method.

Another embodiment of the present invention is to provide an energy storage device comprising the graphene nanostructure.

One embodiment of the present invention is a method of manufacturing a semiconductor device, comprising: preparing a first solution by dispersing graphene powder in deionized water; dispersing the metal oxide in deionized water to prepare a second solution; mixing the first solution and the second solution Adding an aqueous solution containing a nitrogen atom to the mixture, adding an oxidizing agent to the mixture, filtering, washing and drying the mixture, and irradiating the mixture with microwaves Thereby providing a graphene nanostructure production method.

The step of mixing the first solution and the second solution to form a mixture may include mixing the first solution and the second solution to form a mixture, and irradiating ultrasound.

The first solution may contain the deionized water at a weight ratio of 5 ml to 20 ml per 15 mg of the graphene powder.

In the second solution, the deionized water may be mixed at a weight ratio of 5 ml to 20 ml per 0.15 mg of the metal oxide.

The addition amount of the nitrogen atom-containing aqueous solution added to the mixture may be 1 ml to 10 ml.

The amount of the oxidizing agent to be added to the mixture may be 0.1 ml to 1 ml.

The molar concentration of the nitrogen atom-containing aqueous solution may be 0.5M to 2M.

The nitrogen atom-containing aqueous solution may contain ammonia water, methylamine, potassium phthalimide, ethylenediamine or a combination thereof.

The oxidizing agent may include hydrogen peroxide, sodium hypochlorite, chlorine dioxide, or a combination thereof.

The washing may be washing with deionized water.

The step of irradiating the mixture with microwaves may be a step of irradiating microwaves of 300 W to 1,000 W for 1 second to 1,000 seconds.

The metal of the metal oxide may include cobalt, nickel, palladium, iron or a combination thereof.

The metal of the metal oxide may have a particle diameter of 0.1 nm to 1.0 nm.

Another embodiment of the present invention provides a graphene nanostructure produced by the graphene nanostructure production method.

The graphene nanostructure may have a form in which graphene surrounds the metal oxide.

Another embodiment of the present invention provides an energy storage device comprising the graphene nanostructure.

The method of manufacturing a graphene nanostructure according to an embodiment does not use an ionic liquid containing a fluorine component or the like and does not generate noxious gas, and the process is simple, so that it does not take much time to manufacture a graphene nanostructure. In addition, the graphene nanostructure produced by the above-described method has excellent electrochemical performance because graphene surrounds the metal oxide. Thus, the graphene nanostructure can be effectively used for an energy storage device such as a lithium secondary battery and a gas sensor.

Fig. 1 is a flowchart showing a method of manufacturing the graphene nanostructure according to the first embodiment in order.
FIG. 2 is a graph showing the shapes of the graphene nanostructures of Example 1 and Comparative Example 1 during charging / discharging of the energy storage device. FIG.
3 is a scanning electron microscope (SEM) and a projection electron microscope (TEM) photograph of the graphene nanostructure of Example 1 and Comparative Example 1.
FIG. 4 is a graph showing the electrochemical performance of the energy storage device including the graphene nanostructure of Example 1 and Comparative Example 1. FIG.

Hereinafter, an embodiment according to the present invention will be described in detail. However, it should be understood that the present invention is not limited thereto, and the present invention is only defined by the scope of the following claims.

Hereinafter, a method of manufacturing a graphene nanostructure according to an embodiment of the present invention will be described with reference to FIG.

Fig. 1 is a flowchart showing a method of manufacturing the graphene nanostructure according to the first embodiment in order.

In a method of manufacturing a graphene nanostructure according to an embodiment of the present invention, a first solution is prepared by dispersing graphene powder (S100).

Generally, graphene is a material in which carbon atoms are connected in a honeycomb-like hexagonal shape, and has a two-dimensional planar structure as shown in Fig.

The first solution may be prepared by mixing the deionized water at a ratio (weight ratio) of 5 ml to 20 ml per 15 mg of the graphene powder. When the deionized water per 15 mg of graphene powder is mixed within the above range, the graphene powder can be homogeneously dispersed in deionized water in a short time.

Further, the metal oxide is dispersed in deionized water to prepare a second solution (S102).

The second solution may be prepared by mixing the deionized water at a ratio (weight ratio) of 5 ml to 20 ml per 0.15 mg of the metal oxide. When the deionized water per 0.15 mg of the metal oxide is mixed within the above range, the metal oxide can be homogeneously dispersed in the deionized water in a short period of time.

The metal of the metal oxide may include cobalt, nickel, iron or a combination thereof. For example, the metal may be cobalt.

The metal of the metal oxide may have a particle diameter of 0.1 nm to 1.0 nm, for example, 0.1 nm to 0.3 nm.

The first solution and the second solution prepared above are mixed to form a mixture (S104).

At this time, ultrasonic waves may be irradiated to evenly mix the first solution and the second solution. At this time, the ultrasonic irradiation may be performed for 30 minutes to 60 minutes.

The first solution and the second solution are mixed to form a mixture, and then a nitrogen-containing aqueous solution is added thereto (S106).

When the nitrogen atom-containing aqueous solution is added to the mixture, an amine group is formed on the surface of the graphene, so that the metal oxide binds well to the graphene.

The nitrogen atom-containing aqueous solution may include, for example, aqueous ammonia, methylamine, potassium phthalimide, ethylenediamine or a combination thereof.

The molar concentration of the nitrogen atom-containing aqueous solution may be 0.5M to 2M. Since the nitrogen atom-containing aqueous solution having a molar concentration in the above range is not harmful to the human body, the graphene nanostructure can be safely synthesized.

The nitrogen atom-containing aqueous solution may be added to the mixture in an amount of 1 ml to 10 ml. When the nitrogen-containing aqueous solution is added in the above range, the amine group can be formed on the surface of the graphene dispersed in the mixture.

The first solution and the second solution are mixed to form a mixture, and then an oxidizing agent is added thereto (S108). For example, the oxidizing agent may be added to the mixture to which the nitrogen atom-containing aqueous solution is added.

When the oxidizing agent is added, metal oxides bonded to the graphene surface are further oxidized by an aqueous solution containing a nitrogen atom such as ammonia water. As described later, when the oxidized metal oxide is irradiated with microwaves, thermal energy is generated. This thermal energy generates graphene crystal defects and dislocations, so that graphene surrounds the metal oxide.

The oxidant may include, for example, hydrogen peroxide, sodium hypochlorite, chlorine dioxide, or a combination thereof.

The oxidizing agent may be added to the mixture in an amount of 0.1 ml to 1 ml. When the oxidizing agent is added to the above range, the bond between the graphene and the metal oxide is increased. On the other hand, when the oxidizing agent is added to the mixture at a concentration of less than 0.1 ml, the metal oxide is not sufficiently oxidized. When the oxidizing agent is added in an amount exceeding 1 ml, the metal oxide is over-oxidized to increase the electrochemical performance of the graphene nanostructure .

On the other hand, since only an aqueous solution containing a nitrogen atom such as ammonia water and an oxidizing agent such as hydrogen peroxide are added to the above mixture and the ionic liquid containing the fluorine component is not decomposed and used, it is possible to prevent generation of noxious gas have.

The mixture containing the oxidizing agent is filtered, washed, and dried (S110).

The washing may be washing with deionized water.

The filtered, washed and dried mixture is irradiated with microwaves to produce a 3D graphene nanostructure in which graphene surrounds the metal oxide (S112).

The microwave can be irradiated for 1 second to 1,000 seconds at an intensity of 300 W to 1,000 W. In this case, the two-dimensional graphene having a planar structure changes into a three-dimensional structure, so that the metal oxide can be easily covered. In addition, when irradiating the microwave for less than 1 second, it is difficult to change the planar two-dimensional graphene into a three-dimensional structure. When irradiating for more than 1000 seconds, the carbon-based graphene is burned to form carbon dioxide, The pin nano structure is eliminated.

On the other hand, unlike the conventional method in which a nanostructure is manufactured by using the VLS method, only a microwave is irradiated to a dry mixture. Therefore, according to the manufacturing method according to one embodiment, excellent processability and economical efficiency such as shortening the process time can be achieved .

Another embodiment of the present invention provides a graphene nanostructure produced by the graphene nanostructure production method.

The graphene nanostructure has a structure in which graphene surrounds the metal oxide. Therefore, when the graphene nanostructure is used in an energy storage device, the structural stability and electrochemical performance .

The metal of the metal oxide may include cobalt, nickel, palladium, iron or a combination thereof. For example, the metal of the metal oxide may be cobalt.

The metal of the metal oxide may have a particle diameter of 0.1 nm to 1.0 nm, for example, 0.1 nm to 0.3 nm.

Another embodiment of the present invention provides an energy storage device comprising the graphene nanostructure rule.

The energy storage device may include, for example, a secondary battery such as a lithium secondary battery, a hydrogen storage material, a gas sensor, and the like, but is not limited thereto.

Hereinafter, preferred embodiments and comparative examples of the present invention will be described. However, the following examples are only a preferred embodiment of the present invention, and the present invention is not limited to the following examples.

(Preparation of graphene nanostructure)

Example  One

The graphene powder is dispersed in deionized water and the cobalt oxide is dispersed in deionized water by ultrasonic treatment, and then the two solutions are mixed. The mixture is again ultrasonicated and homogeneously dispersed, followed by the addition of 1 M aqueous ammonia, followed by the addition of hydrogen peroxide. Thereafter, the mixture was filtered, washed and dried, and the remaining material was irradiated with microwaves at 700 W for about 500 seconds to prepare a graphene nanostructure.

Comparative Example  One

The graphene powder is dispersed in deionized water and the cobalt oxide is dispersed in deionized water by ultrasonic treatment, and then the two solutions are mixed. The mixture was ultrasonicated again, dispersed homogeneously and then filtered. The remaining material was irradiated with microwaves at 700 W for about 500 seconds to prepare a nanostructure in which plane graphene and metal oxide were mixed.

(evaluation)

Rating 1

FIG. 2A is a graph showing the graphene nanostructure of Comparative Example 1 before charging / discharging the energy storage device, FIG. 2B is a graph showing the graphene nanostructure of Comparative Example 1 after charge / Fig. In the case of the graphene nanostructure of Comparative Example 1, it can be seen that the metal oxide attached to the graphene surface expands and separates from the graphene surface due to charge / discharge due to the graphene maintaining the two-dimensional planar structure, Accordingly, when the graphene nanostructure of Comparative Example 1 is used in a lithium secondary battery or the like, it is predicted that the electrochemical performance is deteriorated.

2 (c) is a graph showing the graphene nanostructure of Example 1 before charging and discharging the energy storage device, and FIG. 2 (d) is a graph showing the graphene nano structure of Example 1 Fig. In the case of the graphene nanostructure of Example 1, since the graphene surrounds the metal oxide with the three-dimensional structure, it can be confirmed that the metal oxide is attached to the graphene regardless of before and after the charge-discharge. Therefore, it can be predicted that the graphene nanostructure of Example 1 will retain structural stability and electrochemical performance when used in an energy storage device or the like.

Rating 2

FIG. 3 (a) is a scanning electron micrograph of the graphene nanostructure of Comparative Example 1, and FIGS. 3 (b) and 3 (c) are scanning electron micrographs of the graphene nanostructure of Example 1. The yellow arrow shown in FIG. 3 (c) means a nano-sized metal oxide. FIG. 3 (d) is a transmission electron microscope photograph of the graphene nanostructure of Example 1, and it is confirmed that a nano-sized (0.21 nm) metal oxide is located inside the graphene.

From this, it can be seen that, unlike Comparative Example 1, the graphene nanostructure of Example 1 encapsulates nano-sized metal oxide in graphene.

Rating 3

4 (a) shows the electrochemical performance of an energy storage device including the graphene nanostructure of Example 1 as an electrode active material by cyclic voltammetry, and FIG. 4 (b) The electrochemical performance of the energy storage device including the graphene nanostructure of Comparative Example 1 and Example 1 as an electrode active material was confirmed at a scan rate, and FIGS. 4 (c) and 4 (d) the electrochemical performance of an energy storage device including the graphene nanostructure of Example 1 as an electrode active material in a galvanostatic charge-discharge method at a current density was confirmed. (In particular, FIG. 4 (d) shows stable electrochemical capacity even after 10,000 charge / discharge cycles).

From this, it can be confirmed that unlike Comparative Example 1, the electrochemical performance of the energy storage device including the graphene nanostructure of Example 1 is excellent.

It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims. As will be understood by those skilled in the art. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive.

Claims (18)

Dispersing graphene powder in deionized water to prepare a first solution,
Dispersing the metal oxide in deionized water to prepare a second solution,
Mixing the first solution and the second solution to form a mixture,
Adding a nitrogen atom-containing aqueous solution to the mixture,
Adding an oxidizing agent to the mixture,
Filtering, washing and drying the mixture, and
Irradiating the mixture with microwaves
≪ / RTI > The method of claim 1,
Mixing the first solution and the second solution to form a mixture comprises:
And mixing the first solution and the second solution to form a mixture, and irradiating ultrasound to the graphene nanostructure. The method of claim 1,
Wherein the first solution is mixed with the deionized water at a weight ratio of 5 ml to 20 ml per 15 mg of the graphene powder. The method of claim 1,
Wherein the second solution is prepared by mixing the deionized water at a weight ratio of 5 to 20 ml per 0.15 mg of the metal oxide. The method of claim 1,
Wherein the amount of the nitrogen atom-containing aqueous solution added to the mixture is 1 ml to 10 ml. The method of claim 1,
Wherein the amount of the oxidizing agent to be added to the mixture is 0.1 ml to 1 ml. The method of claim 1,
Wherein the molar concentration of the nitrogen atom-containing aqueous solution is 0.5M to 2M. The method of claim 1,
Wherein the nitrogen atom-containing aqueous solution comprises ammonia water, methylamine, potassium phthalimide, ethylenediamine or a combination thereof. The method of claim 1,
Wherein the oxidizing agent comprises hydrogen peroxide, sodium hypochlorite, chlorine dioxide, or a combination thereof. Claim 10 has been abandoned due to the setting registration fee. The method of claim 1,
Wherein the cleaning is performed using deionized water. The method of claim 1,
The step of irradiating the mixture with microwaves comprises:
And irradiating a microwave of 300 W to 1,000 W for 1 second to 1,000 seconds. The method of claim 1,
Wherein the metal of the metal oxide comprises cobalt, nickel, palladium, iron, or a combination thereof. The method of claim 1,
Wherein the metal of the metal oxide has a particle diameter of 0.1 nm to 1.0 nm. delete delete delete delete delete

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