WO2022139044A1 - Method for preparing graphene-carbon nanotube composite - Google Patents

Abstract

The present invention relates to a method for preparing a graphene-carbon nanotube composite, the method comprising: 1) a step of controlling the shape of graphene oxide (GO) by mixing a surfactant and GO; 2) a step of reducing the shape-controlled GO; 3) a step of modifying the surface of the reduced GO and the surface of a carbon nanotube; and 4) a step of mixing the surface-modified reduced GO and the surface-modified carbon nanotube. When the graphene-carbon nanotube composite prepared by the preparation method of the present invention is included as an anode material of a lithium secondary battery, a charging capacity (475 mAh/g) more than twice that of a currently developed product may be exhibited. Also, since there is no performance degradation according to the number of charges and discharges, a high-capacity/long-life lithium secondary battery may be prepared.

Description

Graphene-carbon nanotube composite manufacturing method

The present invention relates to a method for manufacturing a graphene-carbon nanotube composite, and specifically, 1) mixing a surfactant and graphene oxide (Graphene Oxide, GO) to control the shape of the graphene oxide; 2) reducing the shape-controlled graphene oxide; 3) modifying the surface of the reduced graphene oxide and carbon nanotubes; 4) It relates to a graphene-carbon nanotube composite manufacturing method comprising the step of mixing the surface-modified reduced graphene oxide and carbon nanotubes.

Recently, interest in energy storage technology is increasing. Efforts for research and development of electrochemical devices are becoming more concrete as the field of application expands to cell phones, camcorders, notebook PCs, and even the energy of electric vehicles.

Electrochemical devices are receiving the most attention in this aspect, and among them, the development of rechargeable batteries that can be charged and discharged is the focus of interest. and research and development of battery design.

A lithium secondary battery is a broad concept including lithium ion, lithium polymer, and lithium ion polymer secondary batteries as well as secondary batteries using lithium metal, and has a high voltage and high energy density.

Anodes of lithium secondary batteries have been mainly developed with carbon-based materials. Structurally, the carbon-based anode active material can reversibly intercalate and detach lithium ions between carbon layers. The carbon-based negative active material has the advantage of having a high capacity, and since the oxidation-reduction potential is low, when a carbon-based negative electrode is used, the carbon-based negative active material has a high potential.

The energy density of secondary batteries for electric vehicles is currently 250Wh/kg (550Wh/L). In order to evolve to 350Wh/kg (800Wh/L) in the future, it should be developed in the direction of increasing the high-capacity active material ratio, increasing the voltage of the electrolyte, and reducing the thickness of the separator. The development of such a high-capacity active material should be accompanied by the development of high-quality/high-concentration CNT paste.

Currently, 5% CNT (carbon nanotube) paste is used for the cathode material of secondary batteries and 1% CNT paste is used for the anode material, but electric vehicles still require a short driving distance and a long charging time.

Therefore, it is necessary to develop positive electrode/negative electrode material active material to overcome this problem, and at the same time improve CNT, an additive, and develop graphene (graphene) additive as a new additive.

An object of the present invention is to provide a method for producing a graphene-carbon nanotube composite and a graphene-carbon nanotube composite prepared by the method.

Objects of the present invention are not limited to the objects mentioned above, and other objects not mentioned will be clearly understood from the description below.

In one embodiment of the present invention, 1) controlling the shape of the graphene oxide by mixing a surfactant and graphene oxide (Graphene Oxide, GO); 2) reducing the shape-controlled graphene oxide; 3) modifying the surface of the reduced graphene oxide and carbon nanotubes; 4) It provides a graphene-carbon nanotube composite manufacturing method comprising the step of mixing the surface-modified reduced graphene oxide and carbon nanotubes.

The surfactant is a cationic surfactant, cetyltrimethyl ammonium bromide (CTAB), hexadecyltrimethyl ammonium bromide (hexadecyltrimethyl ammonium bromide), cetyltrimethyl ammonium chloride (CTAC), cetylpyridinium chloride ( cetylpyridinium chloride, CPC), benzalkonium chloride (BAC), benzethonium chloride (BZT), 5-bromo-5-nitro-1,3-dioxane (5-bromo-5-nitro- 1,3-dioxane), dimethyldioctadecyl ammonium chloride, and dioctadecyldimethyl mmonium bromide (DODAB) may be at least one selected from the group consisting of, but not limited thereto, preferably cetyltrimethyl ammonium chloride (CTAC).

Step 1) may be performed in a polar solvent or a non-polar solvent, and the polar solvent may be methanol, ethanol, propanol, isopropanol, butanol, water, or a mixed solution of two or more thereof, and the non-polar solvent is hexane, toluene, methylene chloride , ethyl acetate, acetone, chloroform, or a mixed solution of two or more thereof, but is not limited thereto.

One of the graphene oxide and carbon nanotubes reduced in step 3) may have an amino group (-NH ₂ ) and the surface of the other one may be modified with a carboxyl group (-COOH).

When any one of the reduced graphene oxide and carbon nanotubes is modified with an amino group (—NH ₂ ), the reduced graphene oxide or carbon nanotubes are mixed with a) an organic molecule containing an amino group and a chlorination reagent, or b) Ammonia (NH ₃ ) It may further include any one of the plasma treatment with. In step a), the solvent may be DMF or DMSO.

The organic molecule containing the amino group is ethylenediamine, o-phenyldiamine, p-phenyldiamine, alanine, arginine, asparagine, cysteine, glutamic acid, glutamine, glycine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine , proline, serine, threonine, tryptophan, tyrosine, valine, dopamine, pyrrolysine, selenocysteine and M2,N2-dimethyl-1,2-butanediamine may be at least one selected from the group consisting of, but limited thereto No, preferably ethylenediamine.

The chlorination reagent may be at least one selected from the group consisting of (COCl) ₂ (oxalyl chloride), SOCl ₂ (thionyl chloride), POCl ₃ (phosphoryl chloride) and PCl ₅ (phosphorus pentachloride), but is limited thereto is not, preferably thionyl chloride (Thionyl chloride).

When the surface of the carbon nanotube is modified with a carboxyl group (-COOH), the method may further include treating the carbon nanotube with an acid solution, wherein the acid solution is a piranha solution, aqua regia solution, hydrochloric acid solution, sulfuric acid solution, and It may be one or more selected from the group consisting of nitric acid solution, but is not limited thereto.

The step 3) may further include the step of surface-modifying the previously reduced graphene oxide with a silane coupling agent.

The silane coupling agent is selected from the group consisting of Aminopropyltriethoxysilane (APTES), Aminopropyltrimethoxysilane (APTMS), 3-mercaptopropyltriethoxysilane (MPTES), 3-mercaptopropyltrimethoxysilane (MPTMS), TetraethylOrthosilicate (TEOS), Tetramethyl Orthosilicate (TMOS), Tetramethyl Orthosilicate (TMOS), TPOS (Tetrapropyl Orthosilicate) selected from the group consisting of It may be one or more, but is not limited thereto, and preferably APTES (Aminopropyltriethoxysilane).

Therefore, according to a preferred embodiment of the present invention, the step of modifying the surface of the reduced graphene oxide in the graphene-carbon nanotube composite manufacturing method of the present invention may be performed in two steps, a) reduced graphene oxide surface-modifying with a silane coupling agent and b) mixing with an organic molecule containing an amino group and a chlorinating reagent.

In the step of mixing the surface-modified reduced graphene oxide and carbon nanotubes in step 4), in addition to the surface-modified reduced graphene oxide and carbon nanotubes, a silane coupling agent, an acidic solution, and isopropanol are further added Preferably, the silane coupling agent is Aminopropyltriethoxysilane (APTES), the acidic solution is hydrochloric acid, and the solvent for the mixing step is DMF or DMSO.

The RGO and the DWCNT surface-modified with the nitric acid solution may be mixed in a weight ratio of 1:1 to 5:1, but is not limited thereto.

The silane coupling agent, isopropanol, and acidic solution may be mixed in a ratio of 13.5 : 86.499 : 0.001, and the silane coupling agent may be increased up to 25%, and in this case, the content of isopropanol is reduced by the increased amount of the silane coupling agent.

According to a preferred embodiment, any one of the reduced graphene oxide and the carbon nanotube has an amino group (-NH ₂ ) and the other is a carboxyl group (-COOH), the surface of which is modified, and the surface of the reduced graphene oxide is modified. And carbon nanotubes are mixed, reacted at 40 to 80° C. for 5 to 15 hours, and finally, a graphene-carbon nanotube composite can be obtained.

According to another embodiment of the present invention, there is provided a graphene-carbon nanotube composite prepared by the above manufacturing method, and the obtained graphene-carbon nanotube composite has an average particle size of 1 to 10 μm.

According to another embodiment of the present invention, there is provided an electrode including the obtained graphene-carbon nanotube composite, and the electrode may be a positive electrode or a negative electrode of a lithium secondary battery, but is not limited thereto.

According to another embodiment of the present invention, there is provided a secondary battery including the electrode.

The lithium secondary battery of the present invention may be manufactured according to a conventional method known in the art. For example, it can be prepared by putting a separator between the positive electrode and the negative electrode and adding an electrolyte in which lithium salt is dissolved.

The electrode of the secondary battery may also be manufactured by a conventional method known in the art. For example, a slurry is prepared by mixing and stirring a solvent, a binder, a conductive material, etc., with a positive electrode active material or a negative electrode active material, if necessary, and then applying (coating) it to a current collector made of a metal material, compressing it, and drying the electrode to manufacture an electrode can do.

When the graphene-carbon nanotube composite manufactured by the manufacturing method of the present invention is included as an anode material of a lithium secondary battery, it exhibits a charging capacity (475 mAh/g) more than twice that of currently developed products, and It is possible to manufacture a high-capacity/high-life lithium secondary battery without performance degradation.

1 is an image showing an SEM photograph of the graphene-carbon nanotube composite prepared by the manufacturing method of the present invention.

2 is a graph showing the results of the charging and discharging experiment of the graphene-carbon nanotube composite prepared by the manufacturing method of the present invention.

In one embodiment of the present invention, 1) controlling the shape of the graphene oxide by mixing a surfactant and graphene oxide (Graphene Oxide, GO); 2) reducing the shape-controlled graphene oxide; 3) modifying the surface of the reduced graphene oxide and carbon nanotubes; 4) It provides a graphene-carbon nanotube composite manufacturing method comprising the step of mixing the surface-modified reduced graphene oxide and carbon nanotubes.

Throughout the specification of the present invention, when a part "includes" a certain component, it means that other components may be further included, rather than excluding other components, unless otherwise stated.

Throughout the specification of the present invention, when a step is located “on” or “before” another step, this means not only a case in which a step is in a direct time-series relationship with another step, but also a step of mixing after each step and Likewise, the order of two steps may include the same rights as in the case of an indirect time-series relationship in which the time-series order may change.

The terms "about", "substantially", etc. to the extent used throughout the specification of the present invention are used in or close to the numerical value when the manufacturing and material tolerances inherent in the stated meaning are presented, and the present invention It is used to prevent an unconscionable infringer from using the disclosure in which exact or absolute figures are mentioned to help the understanding of the As used throughout this specification, the term “step of” or “step of” does not mean “step for.”

<Example>

1. Reduced Graphene Oxide Structure Control

The graphite was pulverized using a ball mill, and the particle size was adjusted to 50 µm or less by sieving. Graphene oxide (GO) was prepared using the graphite. Graphene oxide can be prepared by known methods, for example, by Hummers, Brodie and Staudenmaier methods.

0.15 g of the graphene oxide powder prepared above was dispersed in 125 ml of a 5 wt% CTAB (cetyltrimethyl ammonium bromide) aqueous solution, and then maintained at room temperature for 3 hours. Thereafter, the solvent was dried through a spray drying process to obtain graphene oxide powder. At this time, the spray drying was carried out at a temperature of 180° C. under conditions of 90% aspirator power and 12 feed rate (Bushi spray dryer B-290).

The graphene oxide powder was immersed in 0.1M ascorbic acid (reducing agent) solution, heated to 70° C., and stirred for 2 hours to change graphene oxide into reduced graphene oxide (RGO). Thereafter, the RGO in the solution was filtered, washed with water 3 times, and dried in a freeze dryer at -120° C. for 24 hours to obtain RGO in powder form.

2. Surface modification of carbon nanotubes and reduced graphene oxide

1) Surface modification of carbon nanotubes

Double-walled carbon nanotubes (DWCNTs) were added to a nitric acid solution (HNO ₃ ) having a concentration of 65% (v/v), followed by sonication for 2 hours. DWCNTs are dispersed in nitric acid solution by sonication, and carboxyl groups are generated on the surface of DWCNTs as the acidic solution and DWCNTs react. The acid-treated DWCNTs were washed several times with pure distilled water (DI water) and then dried at 100° C. to obtain a powdery product.

2) Reduced graphene oxide surface modification

(3-Aminopropyl) Triethoxysilane (APTES) containing an amine group and the obtained RGO were added to a 75% (v/v) ethanol solution in a weight ratio of 10:1. At this time, the reaction temperature was 70 ℃, the reaction time was maintained for 12 hours, after the reaction was completed, washed with distilled water and acetone, and dried at 40 ℃ for 24 hours.

3. Preparation of Graphene-Carbon Nanotube Composites

The surface-modified RGO was dispersed in a DMF solvent together with thionyl chloride and ethylenediamine, and then reacted at 120° C. for 12 hours to bond an amino group (—NH ₂ ) to RGO. Then, it was washed again with distilled water and acetone, and dried at 40° C. for 24 hours.

The RGO, the DWCNT surface-modified with the nitric acid solution, and the APTS sol (APTS: IPA: HCl = 13.5: 86.499: 0.001 weight ratio) were dispersed in the DMF solvent and reacted at 60° C. for 10 hours, followed by distilled water and acetone The final graphene-carbon nanotube composite was obtained by washing using and drying at 40° C. for 24 hours. The RGO and DWCNT surface-modified with the nitric acid solution were mixed in a weight ratio of 1:1, and the APTS sol was added in a weight ratio of 2:1 to the mixed weight of RGO and the DWCNT surface-modified with the nitric acid solution (APTS sol: RGO + DWCNT = 2:1).

<Experimental example>

1. Analysis of particle structure and shape

The particle structure of the graphene-carbon nanotube composite prepared according to the example was observed through the SEM image.

Referring to FIG. 1 , the graphene-carbon nanotube composite of the present invention had an average particle size of 2-3 μm, but it was confirmed that the specific surface area exhibited a specific surface area similar to that of general graphene.

The particle size of the graphene-carbon nanotube composite is very small compared to general graphene sold on the market, and the graphene-carbon nanotube composite prepared according to the present invention maintains the specific surface area of general graphene. While doing so, there is an advantage in that the particle size can be manufactured to be small.

2. Measurement of electrochemical properties

The prepared graphene-carbon nanotube composite was used as an anode material to prepare a half cell, and charge/discharge stability was evaluated. For comparison of results, the same experiment was performed using graphite, China's S company graphene cell negative electrode material, China N company graphene cell negative electrode material, and general commercial graphene as negative electrode materials instead of the graphene-carbon nanotube composite.

anode material Initial capacity (mAh/g) After 300 charge/discharge (mAh/g) black smoke 297 162 China S company graphene cell anode material 396 226 China N company graphene cell anode material 348 230 plain graphene 927 204 Composite of Examples 2,433 475

Referring to Table 1 and FIG. 2, it can be seen that the negative electrode material graphite has a reduced charge capacity (mAh/g) when the number of charging and discharging is increased more than 300 times as shown below, and general graphene negative electrode material and Chinese graphene In the case of the fin anode material, it was confirmed that the performance did not decrease even when the number of charging and discharging was increased, but showed a low capacity. (475mAh/g) was confirmed to be more than doubled, and performance degradation was not confirmed according to the number of charge and discharge 300 times.

As described above in detail a specific part of the present invention, for those of ordinary skill in the art, this specific description is only a preferred embodiment, and it is clear that the scope of the present invention is not limited thereto. Accordingly, the substantial scope of the present invention will be defined by the appended claims and their equivalents.

Claims (15)

1) controlling the shape of graphene oxide by mixing a surfactant and graphene oxide (GO); 2) reducing the shape-controlled graphene oxide; 3) modifying the surface of the reduced graphene oxide and carbon nanotubes; 4) Graphene-carbon nanotube composite manufacturing method comprising the step of mixing the surface-modified reduced graphene oxide and carbon nanotubes. According to claim 1, The surfactant is a cationic surfactant, cetyltrimethyl ammonium bromide (CTAB), hexadecyltrimethyl ammonium bromide (hexadecyltrimethyl ammonium bromide), cetyltrimethyl ammonium chloride (CTAC), cetylpyridinium chloride ( cetylpyridinium chloride, CPC), benzalkonium chloride (BAC), benzethonium chloride (BZT), 5-bromo-5-nitro-1,3-dioxane (5-bromo-5-nitro- 1,3-dioxane), dimethyldioctadecyl ammonium chloride (dimethyldioctadecyl ammonium chloride), and dioctadecyldimethyl ammonium bromide (dioctadecyldimethyl mmonium bromide, DODAB) at least one selected from the group consisting of a graphene-carbon nanotube composite manufacturing method. According to claim 1, The step 1) is a graphene-carbon nanotube composite manufacturing method performed in a polar solvent or a non-polar solvent. According to claim 1, One of the graphene oxide and carbon nanotubes reduced in step 3) is an amino group (-NH ₂ ) and the other is a carboxyl group (-COOH), the surface of which is modified, the graphene-carbon nanotube composite manufacturing method. 5. The method of claim 4, When modified with an amino group (—NH ₂ ), the reduced graphene oxide or carbon nanotubes are a) mixed with an organic molecule containing an amino group and a chlorinating reagent, or b) plasma treatment with ammonia (NH ₃ ) Graphene-carbon nanotube composite manufacturing method further comprising any one. 6. The method of claim 5, The organic molecule containing the amino group is ethylenediamine, o-phenyldiamine, p-phenyldiamine, alanine, arginine, asparagine, cysteine, glutamic acid, glutamine, glycine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine , proline, serine, threonine, tryptophan, tyrosine, valine, dopamine, pyrrolysine, selenocysteine, and at least one selected from the group consisting of M2,N2-dimethyl-1,2-butanediamine graphene-carbon nanotube composite manufacturing method. 6. The method of claim 5, The chlorination reagent is at least one selected from the group consisting of (COCl) ₂ (oxalyl chloride), SOCl ₂ (thionyl chloride), POCl ₃ (phosphoryl chloride) and PCl ₅ (phosphorus pentachloride) graphene-carbon nano A method for manufacturing a tube composite. 5. The method of claim 4, When the surface of the carbon nanotube is modified with a carboxyl group (-COOH), the graphene-carbon nanotube composite manufacturing method further comprising the step of treating the carbon nanotube with an acid solution. 9. The method of claim 8, The acid solution is at least one selected from the group consisting of a piranha solution, aqua regia solution, and a nitric acid solution. The method of claim 1, The step 3) graphene-carbon nanotube composite manufacturing method further comprising the step of surface-modifying the previously reduced graphene oxide with a silane coupling agent. 11. The method of claim 10, The silane coupling agent is selected from the group consisting of Aminopropyltriethoxysilane (APTES), Aminopropyltrimethoxysilane (APTMS), 3-mercaptopropyltriethoxysilane (MPTES), 3-mercaptopropyltrimethoxysilane (MPTMS), TetraethylOrthosilicate (TEOS), Tetramethyl Orthosilicate (TMOS), Tetramethyl Orthosilicate (TMOS), TPOS (Tetrapropyl Orthosilicate) selected from the group consisting of A method for manufacturing one or more graphene-carbon nanotube composites. The method of claim 1, The graphene-carbon nanotube composite has an average particle size of 1 to 10 μm. A graphene-carbon nanotube composite prepared by the method of any one of claims 1 to 12. The graphene of claim 13 - an electrode comprising a carbon nanotube composite. A secondary battery comprising the electrode of claim 14 .

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