KR101846946B1 - Nano/micro composite fiber capable of performance electrochemical energy storage and method for fabricating thereof - Google Patents
Nano/micro composite fiber capable of performance electrochemical energy storage and method for fabricating thereof Download PDFInfo
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Abstract
The present invention relates to a fiber composite having electrical energy storage capability, the fiber composite comprising: (a) a microfiber bundle formed by combining a graphene flake and a carbon nanotube as an electrode active material; (b) a nanofiber web that is coated on the surface of a coating material selected from the group consisting of metal, carbon nanotube, activated carbon, and metal oxide nanoparticles so as to allow charge transfer with the microfibers, and surrounds the outside of the microfibers bundle; (c) an electrolyte filled in the micropores of the nanofiber web and the surface of the microfibers; And (d) an insulating film surrounding the nanofiber web and the electrolyte.
Description
The present invention relates to a fiber composite having electrical energy storage capability and a method of manufacturing the same.
Today, electronic devices have evolved rapidly from rigid silicon-based electronic devices to flexible electronic devices and are now evolving beyond flexible to wearable electronic devices. In the future, as it is predicted that the device will become popular as a skin-attachment type electronic device, researches are being made to make a wearable device based on a flexible material as an electric energy storage source.
The fiber-type energy store does not need to carry a heavy battery separately because the cloth is a power supply source, and it is very useful for daily, industrial and military purposes and has high added value because of being greatly restricted in human activity. Since the fiber material with energy storage capacity is harmless to the human body and the risk of explosion is small, a storage device based on a super capacitor, which is safer, superior in durability and relatively simple structure as compared with a lithium-based secondary battery, is mainly studied.
Nano-carbon materials such as Graphene and CNT are very flexible and have high electrical conductivity and specific surface area, so they are generally used as electrodes (electrode active material) for supercapacitors, sensors, batteries or actuators. Much research is underway. However, the conventional graphene and carbon nanotube based composite fibers are difficult to satisfy both the toughness and the mechanical strength of the fiber and the important factors (energy / power density) of the electrochemical energy storage. As a main cause of the improvement of the mechanical strength of the fiber, graphene and a polymer binder for enhancing the bonding strength of carbon nanotubes are added. These polymer binders cause an increase of the equivalent series resistance, so that the output density and the storage density And the characteristics of the energy storage are lowered.
The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to provide a novel graphene flake / carbon nanotube-based fiber composite having mechanical properties required for fibers while maintaining electrical conductivity inherent to the graphene and carbon nanotubes, And a method for manufacturing the same.
In order to accomplish the above object, the present invention provides a method of manufacturing an electrochemical device, comprising: (a) a microfiber bundle formed by graphene flake (GF) and carbon nanotube (CNT) (b) a nanofiber web that is coated on the surface of a coating material selected from the group consisting of metal, carbon nanotube, activated carbon, and metal oxide nanoparticles so as to allow charge transfer with the microfibers, and surrounds the outside of the microfibers bundle; (c) an electrolyte filled in the micropores of the nanofiber web and the surface of the microfibers; And (d) an insulating film surrounding the nanofiber web and the electrolyte.
According to an embodiment of the present invention, the graphene flake and the carbon nanotube are preferably combined at a weight ratio of 9: 1 to 1:10, and it is more preferable that the weight ratio of the graphene flake and the carbon nanotube is nearly equal .
The graphene flakes are preferably chemically reduced so as to have an acid functional group on the surface. The acid functional group is preferably a carboxyl group (-COOH).
The carbon nanotubes are preferably modified with a surfactant having a hydrophilic sulfonic acid group (SO 3 - ).
Preferably, the graphene flake / carbon nanotube microfibers are modified by heat-treating the surface of the microfibers at 60 to 100 ° C. The acid heat treatment significantly increases the electric energy storage capacity. The acid heat treatment is preferably conducted using sulfuric acid, nitric acid, hydrochloric acid or a mixed acid thereof, preferably at 80 to 85 ° C. More preferably, the acid heat treatment is performed at 1 to 5 M sulfuric acid at 80 to 85 ° C.
The polymer material of the nanofiber is selected from the group consisting of polyvinyl alcohol (PVA), polyvinyl pyrrolidone (PVP), polymethyl methacrylate (PMMA), polymethacrylic acid (PMAA), polyacrylic acid (PAA), polyvinyl chloride , Polylactic acid (PLA), polycaprolactone (PCL), polyurethane (PU), polystyrene (PS), polyethylene oxide (PEO), polyvinyl acetate (PVAC), polyacrylonitrile (PAN), nylon, polycarbonate (PC), polyetherimide (PEI), polyester (PET), polyester sulfone (PES), and polybenzimidazole (PBI).
The coating material may vary depending on the purpose of the fiber composite of the present invention. For improving the energy output density of the fiber composite of the present invention, a material having high conductivity, preferably metal, carbon nanotube, or activated carbon may be used as a coating material. For the purpose of improving energy storage density, Metal oxide nanoparticles, preferably manganese dioxide (MnO2), rubidium dioxide (RuO2), gadolinium oxide (Gd2O3) and the like can be used. However, the metal oxide of the present invention is not limited to the above metal oxide.
The metal deposited on the nanofiber web is preferably selected from at least one selected from the group consisting of aluminum, copper, silver, gold, chromium, nickel, platinum, titanium and alloys thereof.
In the present invention, a known liquid electrolyte, a gel electrolyte, and a solid electrolyte (including a polymer electrolyte) may be used as the electrolyte. The liquid electrolyte may be an acidic aqueous solution such as H 2 SO 4 , HClO 4 or H 3 PO 4 , an alkaline aqueous solution such as NaOH or KOH, or an aqueous solution of TEABF 4 / propylene carbonate (PC), TEABF 4 / acetonitrile ) Can also be used, but the present invention is not limited thereto. The gel electrolyte may be an acidic electrolyte such as PVA-H 2 SO 4 , PVA-Na 2 SO 4 , PVA-HClO 4 , PVA-H 3 PO 4 , PVA-CN, Pullulan- Alkaline electrolytes such as NaOH and PVA-KOH may also be used. Solid electrolytes include, but are not limited to, RbAg 4 I 5 , zirconium oxide (ZrO 2 ), sodium beta-alumina, AgI, and the like. The polymer electrolyte may also be applied to the present invention.
According to another aspect of the present invention, there is provided a method for producing microfibers, comprising: (a) wet spinning an aqueous dispersion of graphene flake / carbon nanotube to prepare microfibers; (b) encapsulating the outside of the microfiber bundle with a nanofiber web coated with a coating material selected from the group consisting of metal, carbon nanotube, activated carbon, and metal oxide nanoparticles, and contacting the microfiber bundle with the coating material; (c) filling the micropores of the microfibers and the nanofiber web with an electrolyte; And (d) wrapping the nanofiber web and the electrolyte with an insulating film.
The method may further include the step of heat treating the graphene flake / carbon nanotube microfibers at 60 to 100 ° C using a strong acid after the step (a) or (b) to modify the surface, Treating the graphene flake / carbon nanotube microfibers by heat treatment at 60 to 100 ° C after the electrolyte is filled when the electrolyte is a strong acid.
Preferably, the acid is sulfuric acid, nitric acid or hydrochloric acid and is heat-treated at 80 to 85 ° C. It is preferable that the electrolyte infiltrate the electrolyte using electrophoresis in order to effectively penetrate the fine pores of the microfibers and the nanofiber web.
The graphene flake / carbon nanotube-based fiber composite according to the present invention has a high electric energy storage capacity.
In addition, since the outer surface of the microfiber core is surrounded by the nanofiber web, the ductility and mechanical strength of the fiber composite are effectively increased.
Further, the coating material is coated on the surface of the nanofiber, and the performance of the fiber composite is optimized by selecting a coating material according to the intended use.
Further, since the electrolyte is filled in the micropores of the nanofiber web by the electrolyte impregnation process, a large amount of electrolyte is applied to the inside or the periphery of the microfiber, and the liquid electrolyte is also effectively impregnated and retained by the nanofiber web structure .
On the other hand, an additional step of acid-treating the microfibers formed by combining the graphene flake / carbon nanotubes has an effect of improving the electrical energy storage capacity up to about 44 times.
1 is a schematic view of a cross-sectional structure of a fiber composite according to an embodiment of the present invention.
FIG. 2 is a process diagram showing a manufacturing process of a fiber composite according to an embodiment of the present invention.
FIG. 3 (a) is a SEM photograph of the reduced graphene oxide after immersing the reduced graphene oxide in 4M sulfuric acid aqueous solution, and FIG. 3 (b) is a SEM image after heat treatment at 80 ° C.
FIG. 4 is a cyclic voltammetry graph of reduced graphene oxide paper. The internal area of the black graph represents the energy storage amount before sulfuric acid heat treatment (deactivation) and the internal area of the red graph shows the energy storage amount after sulfuric acid heat treatment (activation).
5 (a) is a graph showing changes in capacitors due to sulfuric acid heat treatment at a temperature of 20 to 90 ° C, and FIG. 5 (b) is a graph showing changes in capacitors due to sulfuric acid heat treatment at 80 ° C, 82 ° C, and 84 ° C .
Fig. 6 is a photograph of a wet-spin-coated gelatin flake / carbon nanotube aqueous dispersion, wherein (a) is a 30 탆 nozzle, and (b) is a 50 탆 nozzle.
7 (a) is a photograph of a nanofiber web manufactured according to an embodiment of the present invention, (b) is a nanofiber web photograph on which a metal is deposited, and (c) shows a change in conductance Fig.
8 (a) is an optical microscope photograph of the fiber composite produced according to an embodiment of the present invention, and (b) is an electron microscope photograph.
9 shows electrochemical characteristics of a fiber composite electrode fabricated according to an embodiment of the present invention (CV curve, scan rate = 30 ms)
(A) a microfiber bundle formed by combining graphene flake (GF) and carbon nanotube (CNT) as an electrode active material; (b) a nanofiber web in which a metal is deposited on a surface of the microfiber bundle so as to cover the outside of the microfibre bundle and allow charge transfer with the microfibers; (c) an electrolyte filled in the micropores of the nanofiber web and the surface of the microfibers; And (d) an insulating film surrounding the nanofiber web and the electrolyte.
As shown in FIG. 1, the fiber composite of the present invention comprises a bundle of
Thus, one of the main features of the present invention is to effectively encapsulate the outside of the core with the nanofiber (2) web, thereby effectively improving the mechanical properties of the fiber composite. The surface of the
The
Meanwhile, another of the main features of the present invention is that the microfibers formed by combining the graphene flake (GF) and the carbon nanotubes (CNT) are immersed in a strong acid, preferably dilute sulfuric acid, at a temperature of about 60 to 100 ° C, To 90 < 0 > C, more preferably 80 to 85 < 0 > C, the surface is physically modified and the electric energy storage ability is remarkably improved. After 4 hours of heat treatment at 80 ~ 85 ℃ for 1 hour, the electric energy storage capacity was increased about 44 times.
As shown in FIG. 2, the present invention provides a method for producing microfibers, comprising: (a) wet spinning an aqueous dispersion of graphene flake / carbon nanotubes to prepare microfibers; (b) encapsulating the outside of the microfiber bundle with a nanofiber web coated with a coating material selected from the group consisting of metal, carbon nanotube, activated carbon, and metal oxide nanoparticles, and contacting the microfiber bundle with the coating material; (c) filling the micropores of the microfibers and the nanofiber web with an electrolyte; And (d) wrapping the nanofiber web and the electrolyte with an insulating film. The present invention also provides a method of producing a fiber composite having an electric energy storage capability.
In addition, it was confirmed that when the microfibers were subjected to the acid heat treatment at 80 to 85 ° C, the surface of the graphene was modified to improve the energy storage capability. The acid heat treatment is performed after the step (a) or after the step (b).
Grapina
The term "graphene" in the present invention is used in a broad sense including graphene oxide (graphene oxide), chemically reduced graphene oxide, chemically modified graphene or graphene oxide do.
In the present invention, the term "Graphene flake " (GF) is a fragment of graphene, and the average length of the graphene flake is preferably 100 to 1000 nm. Graphene has high specific surface area and conductivity and is suitable as an energy storage element.
Various techniques are known as graphene fabrication methods, including chemical vapor deposition (CVD) in which graphene is synthesized using a transition metal that adsorbs carbon well at a high temperature as a catalyst layer, Epitaxial growth method in which the carbon contained therein grows along the texture of the surface, chemical exfoliation in which the graphite is oxidized and separated from the solution and then reduced, or an ionic substance and an organic solvent Nonoxidative exfoliation, which is produced by inducing intercalation of graphite by intercalation followed by layer separation of the dispersion solution by ultracentrifugation, and the like. In the present invention, the method of producing graphene is not limited. However, considering the mass productivity and cost competitiveness, the chemical peeling method is useful and can be manufactured in the form of graphene having a size of 100 to 1000 nm.
The graphene may be graphene oxide (GO) obtained by chemically peeling oxidized graphite, or graphene oxide (reduced GO, rGO) reduced by chemical or high-temperature heat treatment, chemically modified graphene oxide Chemically converted graphene (CCG), and chemically modified reduced graphene (reduced CCG, rCCG). The graphene of the present invention preferably has an acid functional group on the graphene edge portion or on the surface thereof for chemical bonding with a carbon nanotube to be described later. The acid functional group improves the mechanical properties of the microfibers by hydrogen bonding with a surfactant bonded to the carbon nanotubes. The acid functional group is preferably a hydrogen bond-containing carboxyl group (-COOH), and is effectively hydrogen-bonded to the sulfonic acid group (SO 3 - ) of the modified carbon nanotube.
In the graphene oxide prepared by the chemical stripping method, epoxy group and hydroxyl group mainly exist on the graphene fault plane, and various functional groups such as a carboxyl group, a phenol group, a lactone group, a ketone group, a pyrone group and a lactol group exist on the graphene edge. In the present invention, the graphene oxide can be used as such, but since the electrical conductivity is weakened by the presence of functional groups, graphene oxide reduced by chemical or high-temperature heat treatment is more useful. The chemical reduction can be performed by various known reducing agents such as hydrazine such as hydrazine, sodium hydrazine and hydrazine hydrate, hydroquinone, sodium borohydride (NaBH 4 ), ascorbic acid, glucose, . The electrical conductivity of graphene is greatly improved by reduction. It has been reported that when reduced to hydrazine hydrate, the electrical conductivity is improved about 26 times. When used as a chemical reductant such as hydrazine, sodium hydride or sodium borohydride, the epoxy group or hydroxy group on the graphene surface is effectively removed, but the carboxyl group or carbonyl group located at the edge is not easily removed. Therefore, the chemically reduced graphene oxide generally has a carboxyl group at the edge and can be usefully used in the present invention. Hydroxy groups on the surface of graphene can be effectively removed by reduction treatment with concentrated sulfuric acid at a high temperature.
Although graphene does not dissolve well in water, graphen oxide has an acid functional group, particularly a carboxyl group, on the edge or surface as described above, and can be dissolved and dispersed in water, which is a polar solvent. For effective dispersion, sonication or surfactants can be used.
Carbon nanotube
In the present invention, single-walled carbon nanotubes (SWNTs) are more useful in consideration of electrical conductivity and mechanical properties, although multi-walled carbon nanotubes (MWNTs) can be used for carbon nanotubes (CNTs). Carbon nanotubes are non-polar and do not dissolve well in water, a polar solvent. Therefore, it is preferable to disperse the carbon nanotubes using a hydrophilic surfactant for effective water dispersion. Examples of the surfactant include sodium dodecylbenzenesulfonate (SDBS), sodium dodecylsulfonate (SDS), sodium lignosulfonate (SLS), sodium laureth sulfate (SLES), sodium lauryl ether sulfonate (SLES) (CTAC), cetyltrimethylammonium chloride (CTAC), cetylpyridinium chloride (CPC), and the like, anionic surfactants having a hydrophilic sulfonic acid group (SO 3 - ) such as sodium myreth sulfate, ), Cationic surfactants such as dodecyltrimethylammonium bromide (DTAB), tetradecyltrimethylammonium bromide (TTAB), dioctadecyldimethylammonium bromide (DODAB), dimethyl dioctadecylammonium chloride (DODMAC) , 60, 80, Triton X-100, glycerol alkyl esters, glyceryl laurate esters, polyethylene glycol sorbitan alkyl ester (Polyoxyethylene glycol sorbitan alkyl esters may be used. Although not limited in the present invention, it is preferable to disperse carbon nanotubes in water using an anionic surfactant having a hydrophilic sulfonic acid group (SO 3 - ). Ultrasonic processing is also possible for effective dispersion of carbon nanotubes.
Graphene flake / carbon nanotube micro fiber manufacturing
The diameter of the microfibers of the graphene flake / carbon nanotube-based microfibers according to the present invention is less than 1 mm, preferably several to several hundreds of 탆, and can be produced by wet spinning. Wet spinning methods are known from various publications such as
The spinning solution may be prepared in the form of a 5 to 30 wt% graphene flake / carbon nanotube aqueous dispersion. CTAB coagulating solution having a concentration of 1 mg / mL and 37% hydrochloric acid coagulating solution can be usefully used as a coagulating solution.
The weight ratio of graphene flake to carbon nanotube is preferably in the range of 9: 1 to 1:10, more preferably 1: 1.
The spinning stock solution may be prepared by mixing a graphene flake water dispersion and a carbon nanotube water dispersion. Graphene flakes having an acid functional group are easy to disperse in water, but dispersibility can be improved by using a separate surfactant and / or ultrasonic treatment. The graphene flakes without acid functional groups are low in water solubility and can be dispersed by the above-mentioned surfactants and / or ultrasonic treatment. Since carbon nanotubes have low water solubility, they can be dispersed by the above-mentioned surfactant and / or ultrasonic treatment. The carbon nanotube is preferably modified with an anionic surfactant having a sulfonic acid group (SO 3 - ) such as sodium dodecylbenzenesulfonate (SDBS) or sodium dodecylsulfonate (SDS). At this time, the carboxy group (-COOH) of the graphene flake and the sulfonic acid group (SO 3 - ) of the carbon nanotube can be self-aligned in the direction of the fiber axis when hydrogen is radiated through the hydrogen bond and the toughness is increased, It is possible to produce microfibers without the need.
Nanofiber web
The nanofiber web of the present invention is in the form of a nonwoven fabric having an amorphous fiber arrangement, and many fine pores are formed between the nanofibers. The diameter of the nanofibers is less than 1 mu m, preferably several tens to several hundreds of nanometers. Since the nanofiber web surrounds the microfiber bundle with the nanofibers tightly entangled, the toughness and mechanical properties of the fiber composite according to the present invention The strength can be increased.
The nanofibers can be produced by spinning a fiber-spinning polymer using known techniques such as electrospinning, centrifugal electrospinning, flash-electrospinning electrospray, and electrobrown spinning Can be obtained.
Examples of the fiber-spinning polymer include polyvinyl alcohol (PVA), polyvinyl pyrrolidone (PVP), polymethyl methacrylate (PMMA), polymethacrylic acid (PMAA), polyacrylic acid (PAA), polyvinyl chloride , Polylactic acid (PLA), polycaprolactone (PCL), polyurethane (PU), polystyrene (PS), polyethylene oxide (PEO), polyvinyl acetate (PVAC), polyacrylonitrile (PAN), nylon, polycarbonate (PC), polyetherimide (PEI), polyester (PET), polyester sulfone (PES), polybenzimidazole (PBI) and the like.
Examples of the solvent for the polymer include N, N-dimethylformamide (DMF), dimethylsulfoxide (DMSO), dimethylacetamide (DMA), N-methyl-2-pyrrolidinone (NMP), tetrahydrofuran But are not limited to, THF, ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), propylene carbonate (PC)
Coating material on nanofiber web
In the present invention, "coating" is used in the sense of including deposition. The surface of the nanofibers is coated with a coating material. The coating material coated on the nanofiber web is selected from metals, carbon nanotubes, activated carbon, and metal oxide nanoparticles.
The coating material may vary depending on the purpose of the fiber composite of the present invention. For improving the energy output density of the fiber composite of the present invention, a material having high conductivity, preferably metal, carbon nanotube, or activated carbon may be used as a coating material. For the purpose of improving energy storage density, Metal oxide nanoparticles, preferably manganese dioxide (MnO 2 ), rubidium dioxide (RuO 2 ), gadolinium oxide (Gd 2 O 3 ), and the like can be used. However, the metal oxide of the present invention is not limited to the above metal oxide.
When the coating material is a metal, known methods such as metal vapor deposition and metal particle injection are available. The metal may be selected from aluminum, copper, silver, gold, chromium, nickel, platinum, titanium or an alloy thereof. The thickness of the metal layer is in the range of 1 nm to 1 탆, preferably in the range of 20 to 500 nm. The metal vapor deposition may be performed by a known deposition method such as resistive heating evaporation, sputtering, ion plating, arc deposition, or ion beam assisted deposition It is possible.
In the case of metal vapor deposition, the electrical conductivity of the composite fiber structure wrapped in a nanofiber web having a thickness of 20 nm or more is remarkably improved.
The primer layer having non-volatile polarity may be applied to the nanofiber web surface before the deposition of the coating material, or the surface of the nanofiber web may be plasma-treated to impart a polar functional group, thereby improving the deposition efficiency.
The nanofibers coated with the filler may be cut to a predetermined width and wound around the microfibers bundle as a central axis or wrapped in a spiral shape so as to be wrapped.
Electrolyte filling
By filling the graphene flake / carbon nanotube microfibers wrapped with the nanofiber web with an electrolyte, the fiber composite of the present invention has electrical energy storage capability. Electrolyte storage is important at the interface between the electrolyte and the electrode material. Graphene flakes / carbon nanotubes are very useful as electrode materials because they have high specific surface area with porosity. Electrolytes are classified into liquid electrolytes, gel electrolytes, and solid electrolytes (including polymer electrolytes) depending on the conditions. The ionic conductivity, which is the main factor of the electrolyte properties, is generally the highest in liquid electrolytes, and is about 1/1000 of that of liquid electrolytes in solid electrolytes. The gel electrolyte maintains the advantages of the solid phase and has a high ion conductivity, but also exhibits inferior ion conductivity to the liquid electrolyte. Conventionally, the electrolyte of the fiber type energy storage is limited to the gel electrolyte or the solid electrolyte in terms of the characteristics of the product. However, since the fiber composite of the present invention has a nanofiber web in the form of a dense nonwoven fabric, the advantage of effectively impregnating and retaining the liquid electrolyte .
In the present invention, a known liquid electrolyte, a gel electrolyte, and a solid electrolyte (including a polymer electrolyte) may be used as the electrolyte. The liquid electrolyte may be an acidic aqueous solution such as H 2 SO 4 , HClO 4 or H 3 PO 4 , an alkaline aqueous solution such as NaOH or KOH, or an aqueous solution of TEABF 4 / propylene carbonate (PC), TEABF 4 / acetonitrile ) Can also be used, but the present invention is not limited thereto. The gel electrolyte may be an acidic electrolyte such as PVA-H 2 SO 4 , PVA-Na 2 SO 4 , PVA-HClO 4 , PVA-H 3 PO 4 , PVA-CN, Pullulan- Alkaline electrolytes such as NaOH and PVA-KOH may also be used. Solid electrolytes include, but are not limited to, RbAg 4 I 5 , zirconium oxide (ZrO 2 ), sodium beta-alumina, AgI, and the like. The polymer electrolyte may also be applied to the present invention.
The electrolyte impregnation process may be performed by electrophoresis for rapid penetration of the electrolyte.
Surface modification of graphene flake / carbon nanotube microfibers (acid heat treatment)
According to the present invention, when the graphene flake and the carbon nanotube material are heat-treated with an acid, preferably a strong acid such as diluted sulfuric acid, nitric acid, hydrochloric acid, and more preferably with dilute sulfuric acid, the surface of these materials is modified, And it was confirmed that the electric energy storage ability was remarkably improved as the specific surface area was increased.
FIG. 3 (a) is a SEM photograph of the reduced graphene oxide after immersing the reduced graphene oxide in 4M sulfuric acid aqueous solution, and FIG. 3 (b) is a SEM image after heat treatment at 80 ° C.
FIG. 4 is a cyclic voltammetry graph of reduced graphene oxide paper. The internal area of the black graph represents the energy storage amount before sulfuric acid heat treatment (deactivation) and the internal area of the red graph shows the energy storage amount after sulfuric acid heat treatment (activation).
5 (a) is a graph showing changes in capacitors due to sulfuric acid heat treatment at a temperature of 20 to 90 ° C, and FIG. 5 (b) is a graph showing changes in capacitors due to sulfuric acid heat treatment at 80 ° C, 82 ° C, and 84 ° C .
The reduced graphene oxide was immersed in a 4M sulfuric acid aqueous solution for 30 minutes to sufficiently impregnate the sulfuric acid. The wetted graphene was heat-treated at 20 ° C, 40 ° C, 60 ° C, 70 ° C, 80 ° C and 90 ° C for 1 hour As a result, as shown in FIG. 5, it was confirmed that the volumetric capacitance significantly increased at 70 ° C., 80 ° C., and 90 ° C. with respect to other temperatures, and the maximum peak at 80 ° C. As a result of further experiments, heat treatment at 80 ° C, 82 ° C and 84 ° C showed a maximum peak at 80 to 84 ° C. The acid heat treatment of the present invention may be carried out at 60 to 100 캜, preferably 75 to 90 캜, more preferably 80 to 85 캜. As shown in FIG. 4, the cyclic voltammetry of the surface-modified graphene heat-treated at
The acid heat treatment process of graphene flake / carbon nanotube microfibers is preferably carried out before the step of wrapping with the nanofiber web, but it is also useful to carry out the step after the wrapping. The ionization of the metal deposited on the nanofiber web by the sulfuric acid heat treatment was found to be insignificant after the lapping of the nanofiber web.
On the other hand, the nanofiber web wrapping is followed by filling the strong acid electrolyte and performing the heat treatment in the temperature range, so that the electrolyte filling and the heat treatment can be accomplished by one step.
Insulating film treatment
The insulating film of the nanofiber web is to prevent short-circuiting of the metal layer with the external environment, leakage of electrolyte, and protection of the core from an external impact. The insulating layer can be manufactured by injecting or radiating a known insulating material around the fiber core, which can be used as the fiber material, such as an electric wire coating.
Hereinafter, the present invention will be described in detail by way of examples.
Example 1.
(1) Preparation of graphene flake / carbon nanotube microfibers
To prepare graphene flake / carbon nanotube microfibers, a graphene flake water dispersion and a single wall carbon nanotube aqueous dispersion were first prepared.
The graphene flake water dispersion was prepared by reducing an ethoxyl group at 95 ° C over 2 hours by using an excessive amount of hydrazine in an aqueous solution of graphene oxide (GO) prepared by a chemical stripping method, adding a sulfuric acid solution, and stirring vigorously After removing the hydrogels on the surface, it was washed with a large amount of water, recovered through centrifugation and ultrasonicated. The above procedure was repeated 3 times or more, and then 1 wt% sodium dodecylbenzenesulfonate (SDBS) as a surfactant was added and the GF was effectively dispersed in water by ultrasonication.
The single-walled carbon nanotube aqueous dispersion was prepared by sonication treatment for 30 minutes using 1 wt% SDBS of a surfactant.
Fig. 6 is a photograph of a wet-spin-coated gelatin flake / carbon nanotube aqueous dispersion, wherein (a) is a 30 탆 nozzle, and (b) is a 50 탆 nozzle.
As shown in FIG. 6, the resulting graphene flake water dispersion and a single-walled carbon nanotube aqueous dispersion were mixed to prepare a spinning solution, and then wet-spinned continuously onto the CTAB coagulating solution through a 30 탆 and 50 탆 spinning nozzle After coagulation, it was continuously dipped in distilled water (DI water), washed thoroughly, and dried at room temperature to prepare graphene flake / carbon nanotube microfibers.
(2) Production of metal-deposited nanofiber
7 (a) is a photograph of a nanofiber web manufactured according to the present embodiment, (b) is a nanofiber web photograph on which a metal is deposited, and (c) is a graph showing a change in conductance according to a thickness of a metal layer deposition .
Polyvinyl alcohol (PVA), which is a water soluble polymer, was added to a mixed solvent of water / ethanol (10: 1) in an amount of 25% by weight based on the total amount and mixed to prepare a PVA spinning solution.
The PVA spinning stock solution was transferred to a spinning pack and subjected to electrospinning in an irradiation environment of an applied voltage of 15 kV, a spinning distance of 15 cm from the spinning nozzle to the collector, a spinning rate of 10 μl / min, a temperature of 30 ° C. and a relative humidity of 60% To obtain a fibrous web (Fig. 7 (a)). The diameter of the obtained nanofibers was in the range of 400 to 600 nm, and the average diameter was formed at about 500 nm.
The metal deposition of the nanofiber web was performed by resistive heating evaporation. The nanofiber web prepared above was placed in a vacuum chamber, and a tungsten filament as an evaporation source was mounted on a water-cooled evaporation source holder and charged with 5 g of aluminum. The vacuum pump was operated to evacuate the vacuum to 8 × 10 -5 torr. Then, argon (Ar) was irradiated on the surface of the nanofibers using a plasma generator installed in the vacuum chamber, and the surface was cleaned. The plasma treatment was carried out at 400 W for 1 minute, and the flow rate of the argon gas was set to 100 sccm (Standard Cubic Centimeter per Minute). After completion of the cleaning of the nanofiber web, 8 kW of power was applied for 30 seconds to evaporate the aluminum to deposit on the surface of the nanofiber web (Fig. 7 (b)). The thickness of the aluminum layer deposited on the nanofiber web was measured to be about 300 nm.
As a result of the experiment on the thickness of the metal layer deposition, it was confirmed that the conductance was rapidly increased from the metal layer of 20 nm or more as shown in FIG. 7 (c).
(3) Microfiber wrapping with metal-deposited nanofiber
The microfibers prepared in the above (1) were bundled into several tens of layers and then twisted with an electric motor to prepare microfibers. The twist angle of the microfibers is about 30 degrees.
After the metal-deposited nanofibers prepared in (2) were cut to a predetermined width, the nanofibers were wrapped around the microfibers in a spiral manner.
(4) Electrolyte filling
The fibers prepared in (3) above were impregnated with a 1M sulfuric acid aqueous solution and then subjected to electrophoresis so that the aqueous sulfuric acid solution was well penetrated into the micropores of the microfibers and the nanofiber web.
The fiber composite prepared above is shown in Fig. 8 (a) is an optical microscope photograph of a fiber composite produced according to an embodiment of the present invention, and (b) is an electron microscope photograph.
FIG. 9 shows that the prepared fiber composite electrode has high electrical energy storage capacity (CV curve, scan rate = 30 ms) as a result of the electrochemical characteristics test.
Example 2.
(4) H 2 SO 4 / PVA gel electrolyte was used instead of sulfuric acid aqueous solution in the electrolyte filling process.
The H 2 SO 4 / PVA gel electrolyte was prepared by stirring 30 ml of distilled water and 1.67 ml of 1M sulfuric acid for 10 minutes and then adding 3 g of PVA (average molecular weight of about 150,000) and stirring at about 90 ° C for 1 hour.
Example 3.
The graphene flake / carbon nanotube microfibers prepared in (1) were immersed in a 4M sulfuric acid aqueous solution for 30 minutes, and then heat-treated in an oven at 80 ° C for 1 hour. ), (3) and (4) were carried out.
Example 4.
(4) Electrolyte (H 2 SO 4 ) was charged, and the resultant was further heat-treated in an oven at 80 ° C for 1 hour.
Example 5.
(4) Electrolyte (H 2 SO 4 / PVA) was charged and recovered and further heat-treated in an oven at 80 ° C for 1 hour.
Claims (17)
(b) a nanofiber web that is coated on the surface of a coating material selected from the group consisting of metal, carbon nanotube, activated carbon, and metal oxide nanoparticles so as to allow charge transfer with the microfibers, and surrounds the outside of the microfibers bundle;
(c) an electrolyte filled in the micropores of the nanofiber web and the surface of the microfibers; And
(d) an insulating film surrounding the nanofiber web and the electrolyte,
Fiber composite having electrical energy storage capacity.
Wherein the graphene flake is chemically reduced to have graphene oxide or an acid functional group on its surface.
The acid functional group is a carboxyl group (-COOH), a fiber composite having electrical energy storage ability.
Wherein the microfine fiber bundle carbon nanotubes are modified with a surfactant having a hydrophilic sulfonic acid group (SO 3 - ).
Wherein the microfibers formed by combining graphene flakes and carbon nanotubes are modified by heat treatment at 60 to 100 占 폚 in terms of an acid surface.
Wherein the acid is sulfuric acid, nitric acid or hydrochloric acid or a mixed acid thereof, and has an electric energy storage capacity.
Wherein the acid heat treatment is performed at 80 to 85 占 폚.
Wherein the acid heat treatment is performed at 80 to 85 占 폚 in 1M to 5M sulfuric acid.
The nanofiber web may be made of a material selected from the group consisting of polyvinyl alcohol (PVA), polyvinyl pyrrolidone (PVP), polymethyl methacrylate (PMMA), polymethacrylic acid (PMAA), polyacrylic acid (PAA), polyvinyl chloride (PLA), polycaprolactone (PCL), polyurethane (PU), polystyrene (PS), polyethylene oxide (PEO), polyvinyl acetate (PVAC), polyacrylonitrile (PAN), nylon, polycarbonate ), A polyetherimide (PEI), a polyester (PET), a polyester sulfone (PES), and a polybenzimidazole (PBI).
Wherein the metal coated on the nanofiber web is at least one selected from aluminum, copper, silver, gold, chromium, nickel, platinum, titanium or an alloy thereof.
Wherein the metal oxide nanoparticles coated on the nanofiber web are manganese dioxide (MnO 2 ), rubidium dioxide (RuO 2 ), and gadolinium oxide (Gd 2 O 3 ).
Wherein the electrolyte is a liquid electrolyte.
(b) encapsulating the outer surface of a microfiber bundle, in which the microfibers are bundled, with a nanofiber web coated with a coating material selected from metal, carbon nanotube, activated carbon, and metal oxide nanoparticles, ;
(c) filling the micropores of the microfibers and the nanofiber web with an electrolyte; And
(d) wrapping the nanofiber web and the electrolyte with an insulating film.
A method for fabricating a fiber composite having electrical energy storage capability.
Further comprising the step of heat treating the graphene flake / carbon nanotube microfibers at 60 to 100 ° C using a strong acid after the step (a) or (b) to modify the surface of the graphene flake / carbon nanotube microfibers, Lt; / RTI >
Wherein the electrolyte is a strong acid and the electrolyte is filled and then heat-treated at 60 to 100 ° C to thereby surface-modify the graphene flake / carbon nanotube microfibers. In the step (c) Lt; / RTI >
Wherein the acid is sulfuric acid, nitric acid or hydrochloric acid and is heat-treated at 80 to 85 占 폚.
Wherein the electrolyte is filled with micropores of the microfibers and the nanofibrous web using an electrophoresis technique.
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| US20180240609A1 (en) | 2017-02-17 | 2018-08-23 | Aict | High performance nano/micro composite fiber capable of storing electrical energy and method for fabricating thereof |
| CN107275111B (en) * | 2017-07-26 | 2021-04-06 | 齐齐哈尔大学 | Vesicle phase in-situ synthesis of MnO2Active carbon composite material and electrochemical performance |
| US11404222B2 (en) * | 2017-11-13 | 2022-08-02 | Korea Advanced Institute Of Science And Technology | Apparatus for generating electrical energy based on hydrophilic fiber membrane and method of fabricating same |
| US10371910B2 (en) | 2017-12-22 | 2019-08-06 | At&T Intellectual Property I, L.P. | Optical communications cables utilizing topological insulators as optical fiber cores |
| KR102641315B1 (en) * | 2019-04-29 | 2024-02-26 | 한국전기연구원 | Carbon nanotube oxide composites for stretchable energy storage element, and method for producing carbon nanotube oxide composites, and stretchable energy storage element including the same |
| KR102199876B1 (en) * | 2019-06-24 | 2021-01-08 | 순천향대학교 산학협력단 | fibre type supercapacitor and preparation method thereof |
| KR102481903B1 (en) | 2020-12-01 | 2022-12-28 | 전북대학교산학협력단 | Carbon nanofiber composite for energy storage device, electrode including the same, and manufacturing method thereof |
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