Graphene ink composition and method of manufacturing the same

Abstract

The present invention relates to a graphene ink composition including electrically modified graphene, graphene sheets, a binder, and a solvent, and an absolute value of a zeta potential of the electrically modified graphene is 25 mV or more.

Description

Technical Field

[0001] This invention relates to a graphene ink composition and its manufacturing method. Background Technology

[0002] Graphene, a two-dimensional material, refers to a substance in which carbon atoms are arranged in a honeycomb lattice structure. As the thinnest material known to exist, graphene exhibits a higher current density than copper and possesses a variety of excellent properties, including strength, thermal conductivity, and electron mobility. Due to these outstanding properties, there is active research into applying graphene to various fields such as displays, secondary batteries, solar cells, automobiles, and lighting.

[0003] In particular, in industries such as electronics and information communication, the high performance, miniaturization, and lightweighting of electronic devices are becoming industry trends, and graphene, as a material that can meet these industry trends, is receiving much attention.

[0004] Graphene can be synthesized in various ways, and in industry, it is classified according to the production method. Representatively, there are graphene flakes (GF) produced by exfoliating graphene from graphite crystals and chemical vapor deposition (CVD) graphene produced by chemical vapor deposition.

[0005] Since CVD graphene is produced by vaporizing carbon and depositing it onto a metal surface at high temperature, it can produce large-area and high-quality graphene, but it is difficult to mass-produce and implement the process for applying it to actual products.

[0006] In contrast, graphene sheets can be mass-produced at low cost, but their performance is poor and their dispersibility is low, thus limiting their applicability to a limited range of products.

[0007] Therefore, there is a need for novel graphene ink compositions that can be easily applied to practical industries. Summary of the Invention

[0008] The problem that the invention aims to solve

[0009] To address the aforementioned problems, this invention provides a novel graphene ink composition with high dispersibility, which can therefore be applied in practical industries.

[0010] In particular, a graphene ink composition is provided that can improve dispersibility while reducing sheet resistance and increasing thermal conductivity.

[0011] On the other hand, other objects not explicitly stated in this invention can be further considered within the scope that can be readily inferred from the following detailed description and its effects.

[0012] Solution for solving the problem

[0013] To achieve the above objectives, the graphene ink composition of the present invention includes electrochemically modified graphene, graphene sheets, adhesives, and solvents, and the absolute value of the zeta potential of the electrochemically modified graphene is 25 mV or more.

[0014] In one embodiment, the content of the above-mentioned electrochemically modified graphene is from 0.01 wt% to 0.5 wt%.

[0015] In one embodiment, the content of the above-mentioned electrochemically modified graphene is from 0.05 wt% to 0.5 wt%.

[0016] In one embodiment, the elemental content of the electrochemically modified graphene is 76% to 85% carbon, 5% to 25% oxygen, and 2% to 20% nitrogen, and |ON|>3.

[0017] In one embodiment, the graphene sheet has an elemental content of 90% to 99.4% carbon, 0.5% to 5% oxygen, and 0.1% to 5% nitrogen.

[0018] To achieve the above objectives, a method for preparing a graphene ink composition according to other embodiments of the present invention includes: a step of preparing a first colloid in which electrochemically modified graphene is dispersed; a step of preparing a second colloid in which graphene sheets are dispersed; and a step of mixing the first colloid, the second colloid, an adhesive, and a solvent to prepare a graphene ink composition.

[0019] In other embodiments, the steps for preparing the first colloid include: treating graphite sheets with an oxidant and performing a deposition process, then preparing expanded graphene oxide by irradiation with microwaves; peeling the expanded graphene oxide to prepare graphene oxide; mixing the prepared graphene oxide with deionized water to prepare a graphene oxide suspension; and adding an additive for modifying graphene to the graphene oxide suspension and stirring, then preparing the first colloid comprising electrochemically modified graphene using a large-capacity circulating ultrasonic dispersion system.

[0020] In other embodiments, the additives described above are any one of organic monomers or polymers having an amine group, a hydroxyl group, and an azide group.

[0021] In other embodiments, the steps for preparing the second colloid include: treating graphite sheets with an oxidant and performing a deposition process, then preparing expanded graphite by irradiating it with microwaves; peeling the expanded graphite to prepare graphene sheets; and dispersing the peeled graphene sheets to prepare the second colloid.

[0022] In other embodiments, the content of electrochemically modified graphene included in the graphene ink composition prepared by mixing the first colloid, the second colloid, the adhesive, and the solvent is from 0.05 wt% to 0.5 wt%.

[0023] In other embodiments, the content of electrochemically modified graphene included in the graphene ink composition prepared by mixing the first colloid, the second colloid, the adhesive, and the solvent is from 0.01 wt% to 0.5 wt%.

[0024] In other embodiments, the elemental content of the electrochemically modified graphene is 76% to 85% carbon, 5% to 25% oxygen, and 2% to 20% nitrogen, and |ON|>3.

[0025] In other embodiments, the graphene sheet has an elemental content of 90% to 99.4% carbon, 0.5% to 5% oxygen, and 0.1% to 5% nitrogen.

[0026] Invention Effects

[0027] The graphene ink composition according to an embodiment of the present invention comprises both electrochemically modified graphene and graphene sheets with an absolute value of 25 mV or higher for an electrochemical potential, and therefore has excellent dispersibility.

[0028] Furthermore, the graphene ink composition according to an embodiment of the present invention adjusts the content of electrochemically modified graphene to 0.01 wt% to 0.5 wt%, thereby significantly reducing the sheet resistance.

[0029] Furthermore, in the graphene ink composition according to an embodiment of the present invention, the content of electrochemically modified graphene is adjusted to be from 0.05 wt% to 0.5 wt%, thus significantly reducing the sheet resistance while significantly improving the vertical thermal conductivity.

[0030] On the other hand, even if the effects are not explicitly mentioned here, the effects and potential effects that can be expected from the technical features of the present invention and are described in the following description are also considered as the effects described in the description of the present invention. Attached Figure Description

[0031] Figure 1This is a flowchart of a method for manufacturing a graphene ink composition according to an embodiment of the present invention.

[0032] Figure 2 This is a graph showing the sheet resistance measured according to the content of electrochemically modified graphene in the graphene ink composition according to an embodiment of the present invention.

[0033] Figure 3 This is a graph showing the vertical thermal conductivity measured based on the content of electrochemically modified graphene in the graphene ink composition according to an embodiment of the present invention.

[0034] The accompanying drawings are provided for reference and to illustrate the technical concept of the present invention, but the scope of the invention is not limited thereto. Detailed Implementation

[0035] In describing this invention, if it is determined that a related well-known function is obvious to a person skilled in the art and would unnecessarily affect the spirit of the invention, a detailed description thereof will be omitted.

[0036] Figure 1 This is a flowchart of a method for manufacturing a graphene ink composition according to an embodiment of the present invention. (Refer to...) Figure 1 The following describes a method M100 for manufacturing a graphene ink composition according to an embodiment of the present invention.

[0037] First, step S10 is performed to prepare a first colloid containing a dispersion of charged chemically modified graphene.

[0038] The specific description of step S10 for preparing the first colloid includes: step S11 of preparing expanded graphite oxide by irradiating it with microwaves after treating graphite sheets with an oxidant and performing a deposition treatment; step S12 of preparing graphene oxide by exfoliating the expanded graphite oxide; step S13 of preparing a graphene oxide suspension by mixing the prepared graphene oxide with deionized water; and step S14 of preparing the first colloid containing charged chemically modified graphene by using a large-capacity circulating ultrasonic dispersion system after adding an additive for modifying graphene to the graphene oxide suspension and stirring.

[0039] Step S11, preparing expanded graphite oxide, can be performed by depositing graphite sheets in an oxidant for approximately 30 minutes, followed by irradiation with microwaves at a power of 500W to 1000W for 1 to 10 minutes. The oxidant can be a composite oxidant made by mixing two or more of potassium permanganate, sulfuric acid, hydrogen peroxide, or phosphoric acid. The graphite sheets used can have an average diameter of 100μm to 500μm. The graphite oxide obtained by the above method is referred to as microwave-treated expanded graphite oxide (MEGO).

[0040] Next, step S12 is performed to exfoliate the expanded graphene oxide to prepare graphene oxide. Step S12 to exfoliate the expanded graphene oxide to prepare graphene oxide can be performed by chemical exfoliation, for example, by using an improved method known in chemical exfoliation methods that utilizes phosphoric acid, sulfuric acid, and potassium permanganate.

[0041] Next, step S13 is performed to prepare a graphene oxide suspension by mixing the prepared graphene oxide with deionized water. That is, the exfoliated graphene oxide is dispersed in deionized water (DI water) to prepare a graphene oxide suspension. At this time, the graphene oxide suspension consists of 0.05% to 1% by weight of graphene oxide and the balance being deionized water.

[0042] After preparing the graphene oxide suspension, step S14 is performed whereby an additive for modifying graphene is added to the graphene oxide suspension and stirred, and then a first colloid comprising charged chemically modified graphene is prepared by means of a large-capacity circulating ultrasonic dispersion system.

[0043] Specifically, 50 to 150 parts by weight of additives are added to 100 parts by weight of graphene oxide suspension, and the surface of graphene oxide is modified by stirring at 90°C to 120°C for 12 to 36 hours.

[0044] At this point, as an additive, it can be an organic monomer or polymer having amine, hydroxy, and azide groups. As an organic monomer or polymer with an amine group, it can be selected from any one of the group consisting of ethylenediamine, triethylamine, paraphenylenediamine, 3,3',4,4'-tetraaminobiphenyl, 3,3',4,4'-tetraaminoterphenyl, benzidine, 1,5-diaminonaphthalene, (E)-4,4'-(diazene-1,2-diyl)dianiline, ethylenediamine, 1,6-diaminohexane, and 1,8-diaminooctane. Organic monomers or polymers containing hydroxyl groups can be selected from any one of the group consisting of polyvinyl alcohol (PVA), hot strong alkaline solutions (KOH, NaOH), and hydroxylamine. Organic monomers or polymers containing azido groups can be selected from 2-azidoethanol, 3-azidopropane-1-amine, 4-(2-azidoethoxy)-4-oxobutyric acid, methyl 2-azidoethyl-2-bromo-2-propanoate, chlorocarbonate, azido carbonate, dichlorocarbonene, carbene, and aromatic yne. aryne Any one of the groups consisting of ) and nitrogen-based olefins.

[0045] Upon completion of the surface modification reaction, a first colloid is prepared using a large-capacity circulating ultrasonic dispersion system. This first colloid comprises 1 ton / hour of charged chemically modified graphene. The charged chemically modified graphene can then be dispersed in a solvent.

[0046] Solvents that can be used include water, acetone, methyl ethyl ketone, methanol, ethanol, isopropanol, butanol, ethylene glycol, glycol, polyethylene glycol, tetrahydrofuran, dimethylformamide, dimethylacetamide, N-methyl-2-pyrrolidone, hexane, cyclohexanone, toluene, chloroform, distilled water, dichlorobenzene, xylene, trimethylbenzene, pyridine, methylnaphthalene, nitromethane, acrylonitrile, octadecylamine, aniline, dimethyl sulfoxide, methylene chloride, diethylene glycol methyl ethyl ether, ethyl acetate, and any mixture thereof. Co-solvents that can be used include amide series N,N-dimethylformamide (DMF), N-methylpyrrolidone (NMP), ammonia / hydrochloric acid aqueous solutions, α-terpinol, chloroform, methylethyl ketone, and formic acid. acid), nitroethane, 2-ethoxyethanol, 2-methoxyethanol, 2-butoxyethanol, 2-methoxypropanol, glycol, acetone, methanol, ethanol, isopropanol, butanol, ethylene glycol, polyethylene glycol, tetrahydrofuran, dimethylformamide, dimethylacetamide, N-methyl-2-pyrrolidone, hexane, cyclohexanone, toluene, chloroform, distilled water, dichlorobenzene, xylene, trimethylbenzene, pyridine, methylnaphthalene, nitromethane, acrylonitrile, octadecylamine, aniline, dimethyl sulfoxide, methylene chloride, 2-methoxyethanol, γ-butyrolactone (γGBL), benzyl benzoate Benzoate), 1-Methyl-2-pyrrolidinone (NMP), N,N-Dimethylacetamide (DMA), 1,3-Dimethyl-2-imidazolinone (DMEU), 1-Vinyl-2-pyrrolidone (NVP), 1-Dodecyl-2-pyrrolidinone (N12P), N,N-Dimethylformamide (N,Any one of N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), isopropanol (IPA), and 1-octyl-2-pyrrolidone (N8P).

[0047] Electrochemically modified graphene prepared using this method can possess either a negative charge (N-type) or a positive charge (P-type) depending on the type and amount of additives. N-type graphene satisfies O / N > 1, while P-type graphene satisfies O / N < 1. Furthermore, the lateral size of the electrochemically modified graphene ranges from 50 nm to 50,000 nm, and the average thickness is less than 2 nm.

[0048] Table 1 below shows the dispersibility and sheet resistivity of the electrochemically modified graphene from the first colloid, measured based on the atomic ratio of carbon, oxygen, and nitrogen. The sheet resistivity was measured using graphene sheets prepared from the first colloid with a thickness of 500 nm.

[0049] Table 1

[0050]

[0051] *GO: Graphene Oxide*CMG: Charged chemically modified graphene

[0052] Referring to Table 1, it can be confirmed that electrochemically modified graphene has a higher electrokinetic potential and lower sheet resistivity compared to graphene oxide. However, generally, when the absolute value of the electrokinetic potential is above 25 mV, the dispersibility is good, therefore |ON|>3 is preferred.

[0053] In particular, when the carbon content of electrochemically modified graphene is below 75%, the surface resistivity is relatively high, approximately 10. 5 Ω / sq, however, when the carbon content exceeds 75%, the surface resistivity decreases to approximately 10 Ω / sq. 4 The elemental content of the charged modified graphene is preferably 76% to 85% carbon, 5% to 25% oxygen, and 2% to 20% nitrogen.

[0054] Step S20, which prepares the second colloid, can be performed simultaneously or separately from step S10, which prepares the first colloid.

[0055] Step S20 of preparing the second colloid includes: step S21 of preparing expanded graphite; step S22 of peeling the expanded graphite to prepare graphene sheets; and step S23 of dispersing the peeled graphene sheets to prepare the second colloid.

[0056] Step S21, which prepares expanded graphite, can be performed by depositing graphite sheets in an oxidant for approximately 30 minutes, followed by irradiation with microwaves at a power of 500W to 1000W for 1 to 10 minutes. The oxidant can be a composite oxidant made by mixing two or more of potassium permanganate, sulfuric acid, hydrogen peroxide, or phosphoric acid. The expanded graphite sheets prepared by the above method have an average diameter of 100 μm or less. Alternatively, step S21 can be performed using commercially available expanded graphite with an average diameter of 100 μm or less.

[0057] Next, step S22 is performed to peel off the expanded graphite to prepare graphene sheets. Step S22 to peel off the expanded graphite to prepare graphene sheets can be performed using a liquid phase exfoliation method.

[0058] Next, step S23 is performed to disperse the above-exfoliated graphene sheets to prepare a second colloid.

[0059] That is, the exfoliated graphene sheets can be dried and then dispersed in a solvent. The solvent can be the same as the solvent used for the first colloid.

[0060] Furthermore, as shown in Table 1, unlike electrochemically modified graphene, graphene sheets lack electrostatic repulsion and therefore exhibit poor dispersibility in polar solvents. Therefore, to improve the dispersibility of graphene sheets, the second colloid may also include a dispersing agent at a concentration of 1 wt% to 50 wt% relative to the graphene content.

[0061] Dispersing agents can be used for silane compounds that undergo hydrolysis-induced condensation reactions. Silane compounds that undergo hydrolysis-induced condensation reactions can include tetraalkoxysilanes composed of: tetramethoxysilanes, tetraethoxysilanes, tetra-n-propoxysilanes, tetra-i-propoxysilanes, tetra-n-butoxysilanes, and mixtures thereof; methyltrimethoxysilanes, methyltriethoxysilanes, ethyltrimethoxysilanes, ethyltriethoxysilanes, n-propyltrimethoxysilanes, n-propyltriethoxysilanes, i-propyltrimethoxysilanes, i-propyltriethoxysilanes, n-butyltrimethoxysilanes, n-butyltriethoxysilanes, n-pentyltrimethoxysilanes, n-hexyltrimethoxysilanes, n-heptyltrimethoxysilanes, n-octyltrimethoxysilanes, vinyltrimethoxysilanes, etc. Alkenyltriethoxysilane, cyclohexyltrimethoxysilane, cyclohexyltriethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, 3-chloropropyltrimethoxysilane, 3-chloropropyltriethoxysilane, 3,3,3-trifluoropropyltrimethoxysilane, 3,3,3-trifluoropropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 2-hydroxyethyltrimethoxysilane, 2-hydroxyethyltriethoxysilane, 2-hydroxypropyltrimethoxysilane, 2-hydroxypropyltriethoxysilane, 3-hydroxypropyltrimethoxysilane, 3-hydroxypropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-isocyanate-propyltrimethoxysilane 3-Isocyanate-propyltriethoxysilane, 3,3-glycidyl etheroxypropyltrimethoxysilane, 3-glycidyl etheroxypropyltriethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane, 3-(meth)acryloyloxypropyltrimethoxysilane, 3-(meth)acryloyloxypropyltriethoxysilane, 3-ureapropyltrimethoxysilane, 3-ureapropyltriethoxysilane and trialkoxysilanes composed of mixtures thereof; dimethyldimethoxysilane, dimethyldiethoxysilane, diethyldimethoxysilane, diethyldiethoxysilane, di-n-propyldimethoxysilane, di-n-propyldiethyl... Silyl oxysilanes, di-i-propyldimethoxysilanes, di-i-propyldiethoxysilanes, di-n-butyldimethoxysilanes, di-n-butyldiethoxysilanes, di-n-pentyldimethoxysilanes, di-n-pentyldiethoxysilanes, di-n-hexyldimethoxysilanes, di-n-hexyldiethoxysilanes, di-n-heptyldimethoxysilanes, di-n-heptyldiethoxysilanes, di-n-octyldimethoxysilanes, di-n-octyldiethoxysilanes, di-n-cyclohexyldimethoxysilanes, di-n-cyclohexyldiethoxysilanes, diphenyldimethoxysilanes, diphenyldiethoxysilanes, and mixtures thereof constitute a class of alkoxysilanes; at least one selected from the group consisting of silyl oxysilanes.

[0062] The graphene sheet of the second colloid has a lateral size of 0.3 μm to 50 μm and an average thickness of 2 nm to 20 nm. Furthermore, the elemental content of the usable graphene sheet is 90% to 99.4% of carbon, 0.5% to 5% of oxygen, and 0.1% to 5% of nitrogen.

[0063] Next, step S30 is performed to mix the first colloid, the second colloid, the adhesive, and the solvent to prepare the graphene ink composition.

[0064] The first colloid uses electrochemically modified graphene with an absolute zeta potential of 25 mV or higher. As mentioned above, electrochemically modified graphene with an absolute zeta potential of 25 mV or higher is used because, when mixing the first and second colloids, the electrochemically modified graphene needs to be uniformly dispersed and mixed with graphene oxide in order to expect improved performance of the graphene ink composition.

[0065] The adhesive may be selected from at least one group consisting of thermosetting resins, thermoplastic resins, photocurable resins, and conductive polymers. Thermosetting resins may include polyurethane resins, epoxy resins, melamine resins, polyimides, and mixtures thereof. Thermoplastic resins may include polystyrene and its derivatives, polystyrene-butadiene copolymers, polycarbonate, polyvinyl chloride, polysulfone, polyethersulfone, polyetherimide, polyacrylate, polyester, polyimide, polyamic acid, cellulose acetate, polyamide, polyolefin, polymethyl methacrylate, polyetherketone, polyoxyethylene ether, and mixtures thereof. As a photocurable resin, epoxy resin, polyethylene oxide, polyurethane resin, reactive oligomers, and mixtures thereof can be used. The aforementioned reactive oligomers include: epoxy acrylates, polyester acrylates, polyurethane acrylates, polyether acrylates, thiolates, organosilicon polymers, organosilicon copolymers, reactive monomers, and mixtures thereof. The aforementioned reactive monomers, as monofunctional monomers, include: 2-ethylhexyl acrylate, octyl decyl acrylate, isodecyl acrylate, tridecyl methacrylate, 2-phenoxyethyl acrylate, nonylphenolethoxylate monoacrylate, tetrahydrofurfurylate, ethoxyethyl acrylate, hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, hydroxybutyl acrylate, hydroxybutyl methacrylate, etc. Furthermore, reactive monomers, as difunctional monomers, include: 1,3-butanediol diacrylate, 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, diethylene glycol diacrylate, triethylene glycol dimethacrylate, neopentyl glycol diacrylate, ethylene glycol dimethacrylate, tetraethylene glycol methacrylate, polyethylene glycol dimethacrylate, tripropylene glycol diacrylate, 1,6-hexanediol diacrylate, and mixtures thereof. On the other hand, reactive monomers, as trifunctional monomers, include: trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, pentaerythritol triacrylate, glycidylpentatriacrylate, and mixtures thereof. In this type of photocurable resin, benzophenones, benzoildimethyl ketals, acetophenones, anthraquinones, thioxanthones, and mixtures thereof can be added as photoinitiators.As conductive polymers, polythiophene homopolymers, polythiophene copolymers, polyacetylene, polyaniline, polypyrrole, poly(3,4-ethylenedioxythiophene), pentacene compounds, and mixtures thereof can be used. Based on a monolithic graphene ink composition, it may include 1 wt% to 60 wt% binder; the application of the graphene ink composition may vary depending on the binder content.

[0066] The solvent may be the same solvent used in preparing the first colloid and the second colloid, and may include 10 wt% to 98.9 wt% of solvent based on the overall graphene ink composition.

[0067] On the other hand, the component ratio in step S30, which involves mixing the first colloid, the second colloid, the binder, and the solvent to prepare the graphene ink composition, is determined based on the content of electrochemically modified graphene and graphene sheets. At this point, based on the overall graphene ink composition, it may include 0.1 wt% to 30 wt% of electrochemically modified graphene and graphene sheets.

[0068] Table 2 below and Figure 2 It measures the sheet resistance based on the components of a graphene ink composition that can be used as an electrode. The remaining component in the graphene ink composition is a solvent.

[0069] Table 2

[0070]

[0071] *CMG: Charged chemically modified graphene*GF: Graphene flake

[0072] Refer to Table 2 and Figure 2 It is observed that when 0.01 wt% to 0.5 wt% of electrochemically modified graphene is included, the sheet resistivity significantly decreases to below 125 Ω / sq. This is attributed to the activation of the electrical pathways in the graphene ink composition when the electrochemically modified graphene is uniformly dispersed within it. However, when an excessive amount of electrochemically modified graphene is incorporated relative to the graphene sheets, the low sheet resistivity of the electrochemically modified graphene becomes the primary factor, resulting in a decrease in the sheet resistivity of the graphene ink composition.

[0073] That is, the sheet resistance of the graphene ink composition is greatly affected by the relative amounts of chemically modified graphene and graphene sheets. Therefore, in order to significantly reduce the sheet resistance of the graphene ink composition, the graphene ink composition according to an embodiment of the present invention can make the weight ratio of charged chemically modified graphene to the above-mentioned graphene sheets 1:199 to 1:1999.

[0074] Table 3 below and Figure 3 This measures the sheet resistivity based on the components of a graphene ink composition that can be used for thermally conductive adhesives (TIMs). The remaining component in the graphene ink composition is a solvent.

[0075] Table 3

[0076]

[0077] *CMG: Charged chemically modified graphene*GF: Graphene flake

[0078] Refer to Table 3 and Figure 3 It is known that when 0.5 wt% or more of electrochemically modified graphene is included, the vertical thermal conductivity increases to over 7.5 W / m·K. This is attributed to the activation of the thermal conductivity pathways in the graphene ink composition when the electrochemically modified graphene is uniformly dispersed within it. However, when the electrochemically modified graphene is sufficiently incorporated at 1 wt% or more and sufficiently activates the thermal conductivity pathways, a saturation tendency in thermal conductivity occurs. However, to simultaneously achieve the aforementioned effect of reducing sheet resistivity, 0.05 wt% to 0.1 wt% of electrochemically modified graphene may be included.

[0079] On the other hand, the vertical thermal conductivity of the graphene ink composition is greatly affected by the relative amounts of chemically modified graphene and graphene sheets. Therefore, in order to significantly reduce the sheet resistance of the graphene ink composition and simultaneously improve the vertical thermal conductivity, the graphene ink composition according to an embodiment of the present invention can make the weight ratio of charged chemically modified graphene to the above-mentioned graphene sheets 1:399 to 1:1999.

[0080] The scope of protection of this invention is not limited to the description and expression of the embodiments explicitly described above. Furthermore, it should be reiterated that the scope of this invention is not limited by obvious variations or substitutions within the technical field to which this invention pertains.

Claims

1. A graphene ink composition, characterized in that, include: Electrochemically modified graphene, graphene sheets, adhesives and solvents, Furthermore, the absolute value of the electrochemically modified graphene is above 25mV. The electrochemically modified graphene has an elemental content of 76% to 85% carbon, 5% to 25% oxygen, and 2% to 20% nitrogen, with |ON| > 3. The weight ratio of the electrochemically modified graphene to the graphene sheet is 1:39, 1:99, 1:199 to 1:

399.

2. The graphene ink composition according to claim 1, characterized in that, The graphene sheet contains 90% to 99.4% carbon, 0.5% to 5% oxygen, and 0.1% to 5% nitrogen.

3. A method for preparing a graphene ink composition, characterized in that, include: The steps for preparing a first colloid containing electrochemically modified graphene; The steps for preparing a second colloid containing dispersed graphene sheets; and The step of mixing the first colloid, the second colloid, the adhesive, and the solvent to prepare the graphene ink composition. The electrochemically modified graphene has an elemental content of 76% to 85% carbon, 5% to 25% oxygen, and 2% to 20% nitrogen, with |ON| > 3. The electrochemically modified graphene contained in the graphene ink composition prepared by mixing the first colloid, the second colloid, the binder and the solvent has a weight ratio of 1:39, 1:99, 1:199 to 1:399 to the graphene sheet.

4. The method for preparing the graphene ink composition according to claim 3, characterized in that, The steps for preparing the first colloid include: The step of preparing expanded graphite oxide by irradiating it with microwaves after treating graphite sheets with an oxidant and performing a deposition process. The step of peeling the expanded graphene oxide to prepare graphene oxide. The step of preparing a graphene oxide suspension by mixing the prepared graphene oxide with deionized water; and The first colloid comprising electrochemically modified graphene is prepared by adding an additive for modifying graphene to the graphene oxide suspension and stirring, followed by a large-capacity circulating ultrasonic dispersion system.

5. The method for preparing the graphene ink composition according to claim 4, characterized in that, The additive is any one of organic monomers or polymers having amine, hydroxyl, and azido groups.

6. The method for preparing the graphene ink composition according to claim 3, characterized in that, The steps for preparing the second colloid include: Steps for preparing expanded graphite; The step of peeling the expanded graphite to prepare graphene sheets; and The step of dispersing the peeled graphene sheets to prepare the second colloid.

7. The method for preparing the graphene ink composition according to claim 3, characterized in that, The graphene sheet contains 90% to 99.4% carbon, 0.5% to 5% oxygen, and 0.1% to 5% nitrogen.

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