KR101641255B1 - Composition and Method for Preparing Lithium Doped Graphene via Chemical Reaction - Google Patents

Abstract

The present invention relates to a composition for preparing lithium-doped graphene through a chemical reaction and a method for synthesizing lithium-doped graphene using the composition. Thus, the time for synthesizing lithium-doped graphene can be greatly shortened, and the risk of fire and explosion can be eliminated. Various applications can be expected by chemically preparing a lithium-doped graphene solution incidentally.

Description

TECHNICAL FIELD The present invention relates to a composition and a method for preparing lithium-doped graphene through a chemical reaction,

The present invention relates to a composition for preparing lithium-doped graphene through a chemical reaction and a method for synthesizing lithium-doped graphene using the composition.

Oxidized graphene can be synthesized through the process of oxidizing graphite. Among the several methods known to oxidize graphite in the past, the modified hummers method is most effective in oxidizing graphite It is known as a way to synthesize graphene.

The oxidative graphene synthesis method synthesizes oxidized graphene from graphite, which is a raw material, through oxidation in two steps in total. Graphite was preliminarily oxidized in a strong acid atmosphere using potassium persulfate (K ₂ S ₂ O ₈ ) and phosphorus pentoxide (P ₂ O ₅ ), which are the oxidants of the first oxidation reaction, and potassium permanganate KMnO ₄ ) is used to increase the degree of oxidation. After the oxidation, pure silver oxide grains are obtained through a purification process.

Lithium-doped graphene (Li-doped graphene) is used as an electrode material of a lithium ion capacitor. When lithium is pre-doped into an electrode material, the electrode potential is lowered and a potential difference with the counter electrode is increased do. As a result, the operating voltage is increased and the energy density can be improved. Further, lithium doped in graphene in advance can contribute to an increase in discharge capacity and an available voltage range at the initial discharge of the lithium ion capacitor, thereby improving the energy density.

Conventionally, as a method of doping lithium into graphene, there is a method of placing lithium metal on a graphene electrode and inducing doping of lithium ions by applying heat with a driving force for inducing movement of lithium ions , Which is disadvantageous in that it is impossible to control the doping rate.

Another conventional technique is a method of electrochemically doping lithium, which is a method of electrically connecting and short-circuiting a lithium metal used as a providing material of lithium with an electrode, or artificially applying a voltage or an electric current, It is a method of using electric energy as a driving force for inducing the movement of lithium ions. Although the method of doping lithium electrochemically enables the control of the doping rate by controlling the electric energy, the lithium metal is contained in the cell at the time of manufacturing the lithium ion capacitor cell as well as consuming a relatively long time. There is always a risk of fire and explosion.

Numerous references are referenced throughout the specification and are cited therein. The disclosure of the cited document is incorporated herein by reference in its entirety to more clearly describe the state of the art to which the present invention pertains and the content of the present invention.

Korean Registered Patent No. 10-1128654

The present inventors have made efforts to develop a chemical doping method of lithium which can dramatically shorten the synthesis time, eliminate the risk of fire and explosion, and effectively dope lithium. As a result, when graphene oxide is used as the active material, the force of reduction of the graphene oxide to the reduced oxidized graphene acts as a driving force, so that lithium spontaneously reduces the oxidized graphene, And is chemically doped, thereby completing the present invention.

It is therefore an object of the present invention to provide an oxidized graphene composition for the production of lithium-doped graphene.

Another object of the present invention is to provide a method for synthesizing lithium-doped graphene using the above composition.

Other objects and advantages of the present invention will become more apparent from the following detailed description of the invention, claims and drawings.

One aspect of the present invention is to provide an oxidized graphene composition for use in the production of lithium-doped graphene, including graphene oxide, lithium, and a polar organic solvent.

The oxide graphene composition of the present invention is not a method of electrically connecting and short-circuiting lithium metal used as a material for providing lithium or short-circuiting it, or artificially applying a voltage or current to dope lithium into the active material, Lt; RTI ID = 0.0 > of < / RTI > lithium.

When graphene oxide is used as the starting material, the present inventors can spontaneously reduce the graphene oxide and simultaneously be doped on the graphene by taking advantage of the difference in reduction potential between the graphene oxide and lithium. . Here, since the reduction potential of the lithium metal is -3.04 V and the reduction potential of the graphene oxide is approximately -1.0 V, the lithium doping can be effectively performed without artificially applying a voltage or current.

The oxidized graphene contained in the composition of the present invention may be directly manufactured by the Hummers method or purchased or used.

In a preferred embodiment, the oxidized graphene composition of the present invention may further comprise an electron donor selected from a biphenyl-based compound or naphthalene, wherein the electron donor is selected from the group consisting of a catalyst .

When the composition of the present invention further comprises an electron donor, it is advantageous to synthesize lithium-doped graphene in a larger amount even by a simple process such as stirring, heat treatment, ultrasonic wave treatment, or a combination of two or more.

The electron donor acts as an effective electron transporting agent as an anion radical promoter. An electron donor which receives electrons from lithium becomes an anion radical having a very high reactivity and continuously transfers electrons to the graphene oxide, Resulting in the formation of carbanionic graphene species, resulting in the formation of Li-RGO.

As the electron donor, biphenyl-based compounds or phenyl-based anion radical promoters such as naphthalene may be used without limitation. The biphenyl-based compounds include DTBP (4,4'-Di-tert-butylbiphenyl), 3 , 3 ', 5,5'-tetrabromo-1,1'-biphenyl, chlorinated biphenyl, 4- (bromomethyl) biphenyl, methyl biphenyl, '-Dimethyl-1,1'-biphenyl, biphenyl-4-carboxylic acid, biphenyl-4,4'-dithiol, biphenyl bromide, 2-cyano- 4,4'-dicarboxylate, 5- (4'-methyl-2-biphenyl) tetrazole, and combinations thereof, but are not limited thereto.

The solvent may be any organic solvent having polarity for effective dispersion of graphene. Examples of the solvent include N-methyl-2-pyrrolidone (NMP), tetrahydrofuran (THF), dimethylformamide (DMF) , Dichlorobenzene (DCB), toluene, chloroform, methyl chloride, and combinations thereof. However, it is not necessarily limited thereto, and NMP may be preferably used.

As the lithium source, metal lithium may be used regardless of the form such as granules or plate form. A lithium compound capable of generating lithium ions may also be used.

Another aspect of the present invention is a method of manufacturing a semiconductor device, comprising: (i) preparing a graphene oxide composition as described above; And (ii) causing a chemical reaction between the graphene oxide and the lithium in the composition. The present invention also provides a method for synthesizing lithium-doped graphene.

(i) oxidation Grapina  Preparing the composition

In one embodiment of the present invention, the oxidized graphene composition can be prepared by mixing both the graphene oxide and the lithium, the electron donor, and the solvent in a container in a glove box in an argon atmosphere.

In another embodiment of the present invention, since lithium and oxidized graphene may not easily react with each other when the solvent and oxidized graphene, lithium, and electron donor are mixed at the same time and energy is applied, a solution in which lithium is dissolved first is prepared, The graphene oxide graphene composition may be prepared by injecting graphene.

In this case, in order to prepare a solution in which lithium is dissolved first, the solvent and lithium may be put into a container in a glove box in an argon atmosphere, and the container may be sealed to block moisture and air. When the oxidized graphene composition further contains an electron donor, the solvent and the electron donor may be added together when lithium is added.

Then, the solution may be heated in the glove box or taken out to the outside and heated at normal pressure. Depending on the conditions, the pressure may be lowered in the case of heating in the glove box, so that the melting point of lithium may increase and the dissolution may be delayed. It is preferable to take it out to the outside and heat it with stirring at normal pressure.

Next, the graphene oxide composition can be prepared by adding graphene oxide to the prepared solution in the glove box and mixing.

( ii ) Oxidation Graffin and  Steps leading to the chemical reaction of lithium

In an embodiment of the present invention, the chemical reaction between the oxidized graphene and lithium is performed by a method selected from a bath sonication, a tip sonication, a heating, a stirrer, Lt; / RTI >

When appropriate energy is applied to the oxidized graphene composition in any form, it is possible to induce a reaction between lithium and oxidized graphene. For example, in order to minimize the exposure to the outside, It can also apply energy.

When the energy is applied by the heating method, a temperature of about 50 to 100 ° C can be adopted. If the temperature is excessively high, excessive energy may be applied to make the reaction extremely unstable. If the temperature is excessively low, Although the pin reacts spontaneously, the time required to complete the reaction can be further increased.

In the method of the present invention, the amount of lithium doping on the graphene can be controlled by adjusting the amount of lithium supplied, and in the case where the oxidized graphene composition further includes an electron donor, depending on the amount of the electron donor The amount by which lithium is doped can be controlled.

In one embodiment of the present invention, when synthesizing lithium-doped graphene using the above materials, the graphene oxide may be prepared by mixing 12 to 100 mg of graphene oxide, 0.1 to 60 mg of lithium, 10 to 1200 mg of electron donor, 10 to 30 ml of organic solvent The amount of lithium doped in the graphene can be controlled.

In the present invention, by replacing the electrochemical doping method requiring long doping time and the risk of fire and explosion by the chemical doping method, the lithium doping time can be remarkably shortened to about 1 hour and free from the risk of fire and explosion have.

In addition, since the amount of lithium doped in graphene can be controlled finally by controlling the amount of electron donor and the amount of lithium to be reacted with the graphene oxide, it is possible to optimize the lithium doping concentration, Density, and power density.

FIG. 1 is a schematic diagram showing a process of synthesizing graphene oxide by an improved Hummus method from graphite, chemically doping lithium into graphene while simultaneously reducing the graphene oxide using lithium as a reducing agent.
2 shows a conventional electrochemical lithium doping method. The conventional electrochemical method uses 100% lithium metal as a lithium source to form a cell, and lithium metal is removed after doping lithium into the negative electrode.
FIG. 3 is a schematic view showing a process in which graphene oxide, lithium, an electron donor and an organic solvent are mixed and mixed in a glass bottle, and then lithium is graphened chemically by applying energy.
The left side of FIG. 4 shows a state in which lithium reacts in the organic solvent in which the graphene oxide is dispersed, generating bubbles. The right side shows how all the lithium reacted and the solution changed from dark brown to black. Oxidized graphene breaks the π bonds in the carbon structure, reducing absorption in the visible light region, resulting in black color and dark brown color. When the graphene oxide is reduced and the π-bond of carbon is restored, absorption in the visible light region is increased and again black appears.
Figure 5 shows the XPS C 1s spectrum of the graphene oxide. There are oxygen functional groups such as C-OH, CO, C = O, and COOH.
FIG. 6 shows XPS C 1s and Li 1s spectra of lithium-doped graphene prepared using NMP as a solvent. Lithium is doped in LiC _x and LiC ₆ forms.
FIG. 7 shows XPS C 1s and Li 1s spectra of lithium-doped graphene prepared using THF as a solvent. When lithium is LiC _x Lt; / RTI >
Figure 8 shows ICP-AES and component analysis of lithium-doped graphene through chemical reaction with oxidized graphene.
Figure 9 shows the effect of solvents on the ratio of Li ₂ CO ₃ and LiC _x .

Hereinafter, the present invention will be described in more detail with reference to Examples. It is to be understood by those skilled in the art that these embodiments are only for describing the present invention more specifically and that the scope of the present invention is not limited by these embodiments.

Example

≪ Example 1 >

Lithium, an electron donor (DTBP) and NMP (N-methyl-2-pyrrolidone) were added to a glove box in an atmosphere of argon (Ar) (vial). In the above procedure, 0.1 to 7 mg of lithium, 10 to 150 mg of electron donor and 10 ml of NMP were added. The inlet of the glass bottle was sealed to prevent the penetration of water or air into the prepared sample to oxidize the lithium. In order to add energy to the reaction between the graphene oxide and lithium in the prepared sample, ultraprecise ultrasound was performed while heating at 70 ° C, and finally, lithium-doped graphene was synthesized through chemical reaction. Adjusting the amount of lithium introduced can control the amount of lithium doping on the graphene, and increasing the amount of each of the added materials can scale up the amount of finally obtained lithium-doped graphene .

In FIG. 6, it was confirmed that lithium was doped into graphene to form LiC _x and LiC ₆ forms.

≪ Example 2 >

Before introducing graphene oxide as a starting material, an electron donor (DTBP) was dissolved in THF (Tetrahydrofuran), lithium was added thereto, and the mixture was heated at 80 ° C for 12 hours to prepare a THF solution in which lithium was dissolved. The above solution and 12 to 30 mg of graphene oxide were put into a vial and the opening of the glass bottle was sealed. In order to add energy to the reaction between the graphene oxide and lithium in the prepared sample, ultraprecise ultrasound was performed while heating at 70 ° C, and finally, lithium-doped graphene was synthesized through chemical reaction. Adjusting the amount of lithium introduced can control the amount of lithium doping on the graphene, and increasing the amount of each of the added materials can scale up the amount of finally obtained lithium-doped graphene .

In FIG. 7, it was confirmed that lithium was doped into the graphene to form LiC _x .

As a result of Examples 1 and 2, it was confirmed that the graphene oxide graphene had carbon and oxygen in a ratio of nearly 1: 1 by weight, and the weight ratio of oxygen was decreased when doped with lithium. When the electron donor was not removed, the electron donor contained carbon, and the weight ratio of oxygen was relatively low. After the electron donor was removed through the heat treatment, the weight ratio of oxygen to graphene was reduced by ~ 10 wt% The doping concentration was ~9 wt% (Figure 8).

Further, Li ₂ CO _3, and to investigate the effect of solvent on the rate of LiC _x, whereas the its eotneunde The results are shown in Figure 9, in the case of using the experimental results THF as the solvent, the lithium without a significant change in the oxygen percentage doping, In the case of using NMP as a solvent, it is possible to control the degree of reduction and the lithium doping concentration by controlling the amount of the catalyst, and it is confirmed that the proportion of LiC _{x in} the final product is increased because the doping is performed while reducing the graphene graphene.

Claims (10)

(i) preparing a graphene oxide composition comprising graphene oxide, lithium and a polar organic solvent; And
(ii) a step of causing a chemical reaction between the graphene oxide and lithium in the composition
Wherein the chemical reaction of step (ii) is carried out by a method selected from a bath sonication, a tip sonication, a heating, a stirrer and a combination thereof, Wherein the lithium-doped graphene is doped with lithium.
The method of claim 1, wherein the composition further comprises an electron donor selected from biphenyl-based compounds or naphthalene.
The method according to claim 1, wherein the amount of lithium doping in graphene is controlled by controlling the amount of lithium introduced into the composition.
The method of claim 1, wherein the composition further comprises an electron donor selected from a biphenyl-based compound or naphthalene, and the amount of lithium doping is controlled according to an amount of the electron donor.
The method of claim 1, wherein step (ii) is performed under a sealed argon atmosphere.
3. The method of claim 2, wherein the biphenyl-based compound is selected from the group consisting of 4,4'-Di-tert-butylbiphenyl (DTBP), 3,3 ', 5,5'tetrabromo-1,1'- chlorinated biphenyl, 4- (bromomethyl) biphenyl, methyl biphenyl, 4,4'-dimethyl-1,1'-biphenyl, biphenyl-4-carboxylic acid, Dithiol, biphenyl bromide, 2-cyano-4-bromomethyl biphenyl, dimethyl biphenyl-4,4'-dicarboxylate, 5- (4'- Sol, and combinations thereof.
The method of claim 1, wherein the polar organic solvent is selected from the group consisting of N-methyl-2-pyrrolidone, THF, DMF, DMSO, DCB, toluene, chloroform, ≪ / RTI > and combinations thereof.
The method of claim 1, wherein the polar organic solvent is NMP.
The method according to claim 1, wherein the heating is performed at 50 to 100 占 폚. delete

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