KR102678479B1 - Method for Preparing Supercapacitor Electrode by Using Nanoparticles with Improved Dispersibility, Electrode Prepared Thereby and Transparent Supercapacitor Using Same - Google Patents

Abstract

The present invention relates to a method for manufacturing electrodes for supercapacitors using nanoparticles with improved dispersibility, electrodes manufactured thereby, and transparent supercapacitors using the same.
In the present invention, the dispersibility of metal oxide nanoparticles is improved through surface treatment using an organic acid, thereby solving the problem of agglomeration of metal oxide nanoparticles and forming a homogeneous coating. In addition, organic acids can be efficiently removed while maintaining the homogeneity of the coating through a heat treatment process when manufacturing electrodes, thereby solving the problem of organic acids increasing the electrical resistance of the electrode and inhibiting interaction with the electrolyte solution. Therefore, using the present invention, a high-performance supercapacitor with excellent transparency can be manufactured.

Description

Method for manufacturing electrodes for supercapacitors using nanoparticles with improved dispersibility, electrodes manufactured thereby, and transparent supercapacitors using the same {Method for Preparing Supercapacitor Electrode by Using Nanoparticles with Improved Dispersibility, Electrode Prepared Thereby and Transparent Supercapacitor Using Same}

The present invention relates to a method of manufacturing an electrode for a supercapacitor using nanoparticles with improved dispersibility, an electrode manufactured thereby, and a transparent supercapacitor using the same. More specifically, it relates to a metal oxide nano-metal oxide nano particle with excellent dispersibility that is surface-treated with an organic acid. It relates to a method of manufacturing electrodes for supercapacitors using particles, electrodes manufactured thereby, and transparent supercapacitors using the same.

A supercapacitor is a type of energy storage device. It is also called an ultra-high capacity capacitor because its storage capacity is much larger than that of a conventional capacitor. Due to the limitations of fossil fuels and environmental pollution, the development of new renewable energy and the rapid growth of the electric vehicle market have raised the importance of high-performance energy storage devices, leading to the active development of supercapacitors.

Supercapacitors that currently dominate the market use carbon-based electrode materials such as activated carbon. In this regard, Republic of Korea Patent Publication No. 10-2017-0012681 uses porous metal carbide particles as a carbon-based electrode material to increase the specific surface area of the particles, improve electrical conductivity, and manufacture a supercapacitor with high specific capacitance. It describes possible technologies. However, due to the inherent color of carbon-based electrode materials, the transparency of the electrode rapidly decreases even if the thickness of the electrode layer is slightly thickened, so there is a limitation that it is difficult to apply it to high-transparency devices.

In order to manufacture highly transparent supercapacitors, the use of metal oxides has been proposed as a new electrode material that can replace carbon-based electrode materials. For example, Republic of Korea Patent Publication No. 10-2021-0134369 describes a method of forming an electrode material using a metal oxide such as ruthenium oxide.

In this way, using metal oxide nanoparticles as an electrode material for a supercapacitor not only ensures high transparency, but also has the advantage of theoretically improving the capacitance of the electrode due to its high specific surface area. However, metal oxide nanoparticles have low electrical conductivity and agglomeration problems occur during deposition, making it difficult to construct a uniform ultra-thin electrode, making it difficult to demonstrate the unique advantages of metal oxide nanoparticles.

Accordingly, there is a demand for the development of technology that can improve the dispersibility of metal oxide nanoparticles to manufacture supercapacitor electrodes with excellent transparency and capacitance performance.

The purpose of the present invention is to provide a method for manufacturing high-performance supercapacitor electrodes using metal oxide nanoparticles with excellent dispersibility.

Another object of the present invention is to provide an electrode for a supercapacitor manufactured by the above method and having excellent uniformity, transparency, and capacitance.

Another object of the present invention is to provide a high-performance transparent supercapacitor including the electrode for the supercapacitor.

In order to achieve the above object, the present invention includes the steps of coating a dispersion of metal oxide nanoparticles surface-treated with an organic acid on a substrate; and heat-treating the dispersion coating to remove organic acids on the surface of the nanoparticles to form a capacitive material layer.

In the present invention, the metal oxide may be an oxide of a metal selected from the group consisting of Ru, Mn, Co, Ti, Zn, and Ni.

In the present invention, the organic acid may have 10 or more carbon atoms.

In the present invention, the substrate is a transparent substrate coated with a current collector material selected from the group consisting of indium tin oxide (ITO), fluorine-doped tin oxide (FTO), indium zinc oxide (IZO), and aluminum-doped zinc oxide (AZO). It may be a substrate.

In the present invention, the concentration of the dispersion may be 0.1 to 20 mg/ml.

In the present invention, coating of the dispersion may be performed by spin coating, spray coating, doctor blade, or bar coating.

In the present invention, the heat treatment may be performed at a temperature of 120 to 300°C.

In the present invention, the thickness of the capacitive material layer may be 1 to 100 nm.

In the present invention, metal oxide nanoparticles surface-treated with the organic acid can be produced by reacting pristine metal oxide nanoparticles with an organic acid.

In the present invention, the average particle diameter of the pure metal oxide nanoparticles may be 0.5 to 5 nm.

In the present invention, the reaction between the pure metal oxide nanoparticles and the organic acid can be performed at a temperature of 10 to 50°C.

In the present invention, the reaction between the pure metal oxide nanoparticles and the organic acid can be performed under conditions where a polar solvent and a non-polar solvent coexist.

In the present invention, the polar solvent may include one or more solvents selected from the group consisting of water, ethanol, acetone, ammonia, and acetic acid.

In the present invention, the non-polar solvent may include one or more solvents selected from the group consisting of hexane, pentane, heptane, benzene, toluene, xylene, and cyclohexane.

In the present invention, the pure metal oxide nanoparticles can be produced by the reaction of a metal halide and a basic additive.

In the present invention, the basic additive may include one or more selected from the group consisting of LiOH, NaOH, and NH ₄ OH.

The present invention also provides an electrode for a supercapacitor manufactured by the above method.

In the present invention, the visible light transmittance of the electrode may be 70% or more.

The present invention also provides a transparent supercapacitor including the electrode and electrolyte for the supercapacitor.

In the present invention, the transparent supercapacitor may further include a separator.

In the present invention, a homogeneous coating can be formed by solving the aggregation problem of metal oxide nanoparticles through surface treatment using organic acid. In addition, organic acids can be efficiently removed while maintaining the homogeneity of the coating through a heat treatment process when manufacturing electrodes, thereby solving the problem of organic acids increasing the electrical resistance of the electrode and inhibiting interaction with the electrolyte solution. Therefore, using the present invention, a high-performance supercapacitor with excellent transparency can be manufactured.

Figure 1 is a photograph taken immediately after and 15 hours after mixing a pristine RuO ₂ nanoparticle dispersion with hexane and oleic acid in an example of the present invention.
Figure 2 shows FT-IR spectra of pristine RuO ₂ and RuO ₂ -OA nanoparticles measured in an example of the present invention.
Figure 3 is a photograph taken after dispersing RuO ₂ -OA nanoparticles prepared in an example of the present invention at various concentrations.
Figure 4 is a photograph of changes in dispersions of pristine RuO ₂ nanoparticles (a) and RuO ₂ -OA nanoparticles (b) over time in an example of the present invention.
Figure 5 shows TEM images of nanoparticles before (a) and after (b) surface treatment in one embodiment of the present invention.
Figure 6 shows a FE-SEM photograph of a thin film prepared from pristine RuO ₂ nanoparticle dispersion (a) and RuO ₂ -OA nanoparticle dispersion (b) in one embodiment of the present invention.
Figure 7 schematically shows the points at which the transmittance of the thin film was measured in one embodiment of the present invention.
Figure 8 shows the transmittance measurement results of thin films of pristine RuO ₂ nanoparticles (a) and RuO ₂ -OA nanoparticles (b) prepared in an example of the present invention.
Figure 9 is a graph showing the average calculated from the transmittance measurement results of Figure 8.
Figure 10 shows the FT-IR spectrum (a) at each heat treatment temperature of a thin film manufactured according to an embodiment of the present invention and the FT-IR spectrum (b) of nanoparticles before and after surface treatment.
Figure 11 shows the water contact angle at each heat treatment temperature of a thin film manufactured according to an embodiment of the present invention.
Figure 12 is a graph showing FT-IR results and water contact angle according to heat treatment temperature of a thin film manufactured according to an embodiment of the present invention.
Figure 13 shows a FE-SEM photograph after heat treatment of a RuO ₂ -OA nanoparticle thin film according to an embodiment of the present invention.
Figure 14 shows XRD results after heat treatment of a RuO ₂ -OA nanoparticle thin film according to an embodiment of the present invention.
Figure 15 shows CV contour results for each heat treatment temperature of a thin film manufactured according to an embodiment of the present invention.
FIG. 16 is a graph of area capacitance calculated from the CV contour results of FIG. 15.
Figure 17 shows the results of measuring the visible light transmittance of the electrode according to the dispersion concentration and number of coatings in one embodiment of the present invention.
Figure 18 is a graph showing the average transmittance of the electrode according to the dispersion concentration and number of coatings in one embodiment of the present invention.
Figure 19 shows a transmittance graph of an electrode manufactured according to an embodiment of the present invention and a photograph of the electrode at each transmittance condition.
Figure 20 shows the RuO ₂ thin film thickness as a function of absorbance in an electrode manufactured according to an embodiment of the present invention.
Figure 21 is a graph comparing the area capacitance of electrodes with similar transmittances in one embodiment of the present invention.
Figure 22 shows CV contours measured for electrodes with different transmittances in one embodiment of the present invention.
Figure 23 is a graph comparing the area capacitance of a transparent electrode according to an embodiment of the present invention and a conventional transparent electrode.
Figure 24 shows the area capacitance measured for the electrode manufactured according to an embodiment of the present invention as a function of scanning speed.
Figure 25 is a deconvolution result for an electrode manufactured according to an embodiment of the present invention.
Figure 26 is a photograph of a two-electrode cell manufactured according to one embodiment of the present invention.
Figure 27 is a graph of the transmittance of a two-electrode cell manufactured according to an embodiment of the present invention.
Figure 28 is a CV measurement result of a two-electrode cell manufactured according to an embodiment of the present invention.
Figure 29 is a constant current charge/discharge (GCD) curve of a two-electrode cell manufactured according to an embodiment of the present invention.
Figure 30 shows a graph of capacitance retention of a two-electrode cell manufactured according to one embodiment of the present invention.
Figure 31 shows electrochemical impedance spectroscopy (EIS) measurement results of a two-electrode cell manufactured according to an embodiment of the present invention.
Figure 32 shows a graph of capacitance retention according to the number of GCD cycles of a two-electrode cell manufactured according to an embodiment of the present invention.
Figure 33 is a photograph of a full-cell manufactured according to an embodiment of the present invention.
Figure 34 shows the results of transmittance measurement of a full-cell manufactured according to an embodiment of the present invention.
Figure 35 is a CV measurement result of a full-cell manufactured according to an embodiment of the present invention.
Figure 36 is a graph of the area capacitance of a full-cell manufactured according to an embodiment of the present invention.

Hereinafter, specific implementation forms of the present invention will be described in more detail. Unless otherwise defined, all technical and scientific terms used in this specification have the same meaning as commonly understood by a person skilled in the art to which the present invention pertains. In general, the nomenclature used herein is well known and commonly used in the art.

The present invention relates to metal oxide nanoparticles with improved dispersibility, an electrode for a supercapacitor manufactured using the same, and a transparent supercapacitor including the electrode.

In the present invention, the dispersibility of metal oxide nanoparticles is improved through surface treatment using an organic acid, thereby solving the problem of agglomeration of metal oxide nanoparticles and forming a homogeneous coating. In addition, organic acids can be efficiently removed while maintaining the homogeneity of the coating through a heat treatment process when manufacturing electrodes, thereby solving the problem of organic acids increasing the electrical resistance of the electrode and inhibiting interaction with the electrolyte solution. Therefore, using the present invention, a high-performance supercapacitor with excellent transparency can be manufactured.

The metal oxide nanoparticles with improved dispersibility used in the present invention are characterized by surface treatment with an organic acid.

In the present invention, the metal oxide nanoparticle is an oxide of a metal selected from the group consisting of Ru, Mn, Co, Ti, Zn, and Ni, for example, RuO ₂ , MnO ₂ , Mn ₃ O ₄ , Co ₃ O ₄ , TiO ₂ , may be nanoparticles of a metal oxide selected from the group consisting of ZnO and NiO. The metal oxides correspond to capacitive materials and can be applied to the electrodes of a supercapacitor to induce an electrochemical redox reaction.

In the present invention, the organic acid may have 10 or more carbon atoms. Preferably, the organic acid may have 13 or more carbon atoms, for example, 16 to 20 carbon atoms.

In the present invention, the organic acid may include fatty acid. The fatty acid may be an unsaturated fatty acid having one or more carbon-carbon double bonds within the molecule.

Specifically, the organic acids used in the present invention include myristoleic acid, palmitoleic acid, sapienic acid, oleic acid, elaidic acid, vaccenic acid, linoleic acid, linoelaidic acid, α-linolenic acid, arachidonic acid, eicosapentaenoic acid, It may include erucic acid, docosahexaenoic acid, etc., and oleic acid, elaidic acid, vaccenic acid, palmitoleic acid, sapienic acid, etc. may be preferably used.

In the present invention, metal oxide nanoparticles surface-treated with the organic acid can be produced by reacting pristine metal oxide nanoparticles with an organic acid. In one embodiment of the present invention, the pure metal oxide nanoparticles may be produced by the reaction of a metal halide and a basic additive.

In an exemplary embodiment of the present invention, the pure metal oxide nanoparticles include preparing a suspension by adding a basic additive to a metal halide; and centrifuging the suspension to obtain metal oxide nanoparticles.

The metal halide used in the suspension preparation step is a precursor of a metal oxide and consists of a metal selected from the group consisting of Ru, Mn, Co, Ti, Zn, and Ni, and a halogen selected from the group consisting of F, Cl, Br, and I. It may contain one or more types of compounds. For example, in the case of chloride, RuCl ₃ , MnCl ₂ , CoCl ₂ , TiCl ₂ , TiCl ₄ , ZnCl ₂ , NiCl _2, etc. may be used.

LiOH, NaOH, NH ₄ OH, etc. can be used as basic additives used in the suspension preparation step. In the present invention, it is preferable to use LiOH as a basic additive because it can improve the specific surface area of the metal oxide nanoparticles produced.

In the suspension preparation step, the solvent for the metal halide may be an organic solvent, and the basic additive may be added in the form of an aqueous solution. Additionally, the molar concentration ratio of the metal halide solution and the basic additive solution may be 1:1 to 1:10, preferably 1:3 to 1:8.

Mixing of the metal halide and basic additive can be performed at a temperature of 20°C or lower, and a suspension can be prepared through stirring. Thereafter, the prepared suspension can be centrifuged to obtain metal oxide nanoparticles.

In the present invention, the centrifugation may be performed within conditions of 1,000 rpm to 10,000 rpm and may be performed for 1 minute to 10 minutes. Metal oxide in the form of nanoparticles can be obtained through centrifugation, then washed and used in subsequent processes.

The metal oxide nanoparticles obtained by the above method are pure (pristine) metal oxide nanoparticles. In the present invention, the pure metal oxide nanoparticles refer to nanoparticles in a state in which no organic acid is bound to the surface, that is, before surface treatment.

In the present invention, the size (average particle diameter) of pure metal oxide nanoparticles may be 0.5 to 5 nm, preferably 1 to 2 nm. By using such small-sized nanoparticles, ions can efficiently contact the electrode by improving the specific surface area of the nanoparticles.

Metal oxide nanoparticles are a supercapacitor electrode material that can replace carbon-based electrode materials. By using metal oxide nanoparticles, unlike carbon-based materials, transparency can be secured and the specific capacitance of the electrode is improved due to the high specific surface area. There is an advantage to being able to do it. However, metal oxide nanoparticles have a limitation in that it is difficult to achieve excellent capacitance when used in actual supercapacitor manufacturing due to the problem of agglomeration during the deposition process.

The present invention is intended to solve the problem of agglomeration of metal oxide nanoparticles and manufacture high-performance electrodes for supercapacitors. Dispersibility can be improved by surface treating pristine metal oxide nanoparticles by reacting them with organic acid. .

In the surface treatment step, the reaction between pure metal oxide nanoparticles and organic acid may be performed through stirring and may be carried out at a temperature of 10 to 50°C, for example, 20 to 30°C. Additionally, stirring may be performed for 1 to 24 hours, for example, 10 to 18 hours. In the above reaction, the ratio of the weight (g) of pure metal oxide nanoparticles and the volume (ml) of organic acid may be 1:100 to 50:100, preferably 5:100 to 20:100.

In the present invention, the reaction between the pure metal oxide nanoparticles and the organic acid can be performed under conditions where a polar solvent and a non-polar solvent coexist. As a result, organic acids can be easily conjugated to the surface of metal oxide nanoparticles through van der Waals interactions at the nonpolar/polar interface. Therefore, the surface treatment reaction can easily proceed even at room temperature without heating. At this time, the polar solvent and the non-polar solvent may be used in a volume ratio of 1:5 to 5:1, for example, 1:2 to 2:1.

In the present invention, polar solvents may include water, ethanol, acetone, ammonia, acetic acid, etc., and non-polar solvents may include hexane, pentane, heptane, benzene, toluene, xylene, cyclohexane, etc.

In an exemplary embodiment of the present invention, the reaction may be performed by mixing a dispersion of pure metal oxide in a polar solvent, a non-polar solvent, and an organic acid. When a non-polar solvent and an organic acid are added to a dispersion in which metal oxide nanoparticles are dispersed in a polar solvent, a phenomenon occurs in which the metal oxide nanoparticles move toward the non-polar solvent, and through this, the metal oxide nanoparticles are surface treated with an organic acid.

In the present invention, the pure metal oxide nanoparticle dispersion may be used at a concentration of 1 to 50 mg/ml, preferably 5 to 20 mg/ml.

In the present invention, agglomeration between nanoparticles can be prevented and dispersibility can be improved by treating metal oxide nanoparticles with an organic acid. Accordingly, the nanoparticles of the present invention are easy to coat and can produce a homogeneous thin film, so when used to manufacture a supercapacitor electrode, an electrode with excellent uniformity can be manufactured.

The present invention also relates to a method of manufacturing an electrode using metal oxide nanoparticles with improved dispersibility.

Metal oxide nanoparticles surface-treated with organic acid have excellent dispersibility, so it is possible to manufacture a homogeneous thin film, making it possible to manufacture high-performance supercapacitor electrodes and ensure transparency of the electrode.

In the present invention, the electrode for a supercapacitor includes the steps of coating a dispersion of metal oxide nanoparticles surface-treated with an organic acid on a substrate; And it can be prepared by heat treating the dispersion coating to remove organic acids on the surface of the nanoparticles. Accordingly, an electrode having a structure including a substrate and a capacitive material layer formed on the substrate and containing metal oxide nanoparticles can be manufactured.

The substrate used to manufacture the electrode of the present invention includes a current collector substrate that can be used to manufacture a transparent supercapacitor, such as ITO (indium tin oxide), FTO (fluorine-doped tin oxide), IZO (indium zinc oxide), and AZO. A transparent substrate coated with a current collector material such as aluminum-doped zinc oxide can be used.

To form a capacitive material layer on the substrate, a dispersion of metal oxide nanoparticles surface-treated with an organic acid is first coated.

As described above, the metal oxide may refer to an oxide of a metal selected from the group consisting of Ru, Mn, Co, Ti, Zn, and Ni, and the nanoparticles may be surface-treated with an organic acid having 10 or more carbon atoms.

In the present invention, the dispersion medium used to disperse metal oxide nanoparticles may include an organic solvent, water, or a mixture thereof. For example, the organic solvent may be a C1 to C10 alcohol, preferably a C6 to C8 alcohol.

In the dispersion coating step, the properties of the electrode can be adjusted by adjusting the concentration of the dispersion. For example, a dispersion having a concentration of 0.1 to 20 mg/ml can be used. If the concentration of the dispersion is too high, the transparency of the electrode may decrease, and if the concentration is too low, the performance of the supercapacitor, such as electrostatic capacity, may be insufficient.

In the dispersion coating step, the transparency and capacitance performance of the electrode can be adjusted by adjusting the concentration of the dispersion and the number of coatings. In an embodiment of the present invention, when using a dispersion of metal oxide nanoparticles surface-treated with an organic acid, an electrode was manufactured by coating the dispersion once with a specific concentration, and an electrode was manufactured by coating the dispersion with a concentration half of the above concentration twice. It was confirmed that the electrodes had little difference in terms of transmittance and capacitance. Accordingly, the use of the present invention is advantageous in that the transmittance and capacitance of the electrode manufactured can be easily and accurately controlled by controlling the concentration and number of coatings of the nanoparticle dispersion.

As a coating method for the dispersion, spin coating, spray coating, doctor blade, bar coating, etc. can be used. Spin coating is used in terms of process convenience and uniformity. This can be preferably used, and spray coating can be preferably used to manufacture large-area devices.

In the present invention, a capacitive material layer can be formed by heat treating the dispersion coating to remove the organic acid on the surface of the nanoparticles. Through the heat treatment, an electrode for a supercapacitor with excellent capacitance performance can be manufactured.

The organic acid present on the surface of the nanoparticle improves the dispersibility of the nanoparticle in the dispersion and thus enables the formation of a uniform coating. However, when applied to an electrode, resistance problems may occur due to the organic acid, and the hydrophobic part of the organic acid may occur. This may impede the penetration of the electrolyte and reduce the performance of the electrode.

The present invention is intended to solve this problem, and it is possible to manufacture an electrode with excellent performance by removing organic acids without damaging the morphology or crystal phase of the thin film through heat treatment after dispersion coating.

In the present invention, the heat treatment step may be performed at 120 to 300°C, preferably 150 to 250°C, and heat treatment at 180 to 220°C is preferred in that the electrostatic capacity of the electrode can be greatly improved. If heat treatment is performed in the above temperature range, a homogeneous thin film can be maintained while removing organic acids. However, if the heat treatment temperature is low, organic acids may remain on the surface of the nanoparticles, which may have a negative effect on capacitance, and if the heat treatment temperature is too high, Even in this case, the capacitance may actually decrease. In an example of the present invention, it was confirmed that when the dispersion coating was heat treated at 200°C, the capacitance was greatly improved without deteriorating the surface morphology or crystallinity.

In the present invention, the heat treatment step may be performed for 10 to 120 minutes, preferably 30 to 90 minutes.

Through the heat treatment step, a capacitive material layer containing metal oxide nanoparticles from which the organic acid has been removed can be formed. Since there is no organic acid in the capacitive material layer formed according to the present invention, problems of increasing electrical resistance and decreasing wettability of the electrode surface do not occur, and using this, a high-performance supercapacitor can be manufactured.

The thickness of the capacitive material layer may vary depending on the concentration of the dispersion, the number of coatings, etc., and may be 1 to 100 nm, for example, 2 to 50 nm. If the thickness of the capacitive material layer is too thick, electrical conductivity may decrease, but using the present invention, it is possible to form the capacitive material layer in the form of an ultra-thin film with a thickness of 10 nm or less, thereby manufacturing an electrode with excellent performance and high transparency. can do.

The electrode for a transparent supercapacitor manufactured according to the present invention can exhibit visible light transmittance of 70% or more, preferably 80% or more. In addition, using the present invention, it is possible to achieve visible light transmittance of 90% or more, preferably 95% or more, and more preferably 97% or more depending on the concentration of the dispersion.

Using this method, a uniform capacitive material layer can be formed with small-sized metal oxide nanoparticles, and since no organic acid remains in the capacitive material layer, problems with electrical resistance caused by organic acid and problems with contact with the electrolyte do not appear. Therefore, the excellent capacitance characteristics of the metal oxide can be effectively exhibited.

Accordingly, the present invention can also provide a supercapacitor including the electrode for the supercapacitor. The supercapacitor of the present invention may be a transparent supercapacitor with high visible light transmittance.

The transparent supercapacitor of the present invention may include an electrode manufactured by the electrode manufacturing method. Specifically, the transparent supercapacitor of the present invention may include a transparent supercapacitor electrode including a current collector and a capacitive material layer, and an electrolyte.

In the transparent supercapacitor electrode of the present invention, the current collector serves to transfer electrons to the outside, and the capacitive material can serve to enable charging and discharging of the supercapacitor through an oxidation-reduction reaction.

The electrolyte is a material that acts as a passage for ions to move, and an aqueous electrolyte can be used in the supercapacitor of the present invention. The aqueous electrolyte may be an acid, base, or inorganic salt such as sulfuric acid (H ₂ SO ₄ ), potassium hydroxide (KOH), sodium hydroxide (NaOH), or potassium chloride (KCl), and may be dissolved in distilled water, deionized water, etc. can be used

The transparent supercapacitor of the present invention may further include a separator between electrodes.

The separator is disposed between the anode and the cathode and serves to enable the transfer of ions in the electrolyte while separating the electrodes. The separator may be an insulating thin film with high ion permeability and mechanical strength, for example, a polymer thin film such as polypropylene (PP) or polyethylene (PE).

According to the present invention, the dispersibility of metal oxide nanoparticles is improved by treatment with organic acid, making it possible to manufacture a thin film with a homogeneous surface. By removing the organic acid through heat treatment, the homogeneity of the thin film is maintained while maintaining the capacitance, response speed, and Electrical performance can be greatly improved. Additionally, the transparency and capacitance of the manufactured electrode can be adjusted by adjusting the concentration of the nanoparticle dispersion and the number of coatings. Therefore, if the present invention is used to manufacture supercapacitor electrodes, a highly transparent supercapacitor with excellent capacitance and response speed can be manufactured.

Example

The present invention will be described in more detail through examples below. However, these examples show some experimental methods and configurations to illustratively illustrate the present invention, and the scope of the present invention is not limited to these examples.

Preparation Example 1: Preparation of metal oxide nanoparticles surface treated with organic acid

Surface treatment of metal oxide nanoparticles:

Metal oxide nanoparticles surface-treated with organic acid were synthesized using phase-transfer and precipitation methods.

_First , 0.02M ruthenium chloride hydrate (RuCl ₃ · , Sigma-Aldrich) was slowly added to the aqueous solution under vigorous stirring to form a dark brown suspension. The product was centrifuged at 5,000 rpm for 5 minutes and washed three times with acetone.

0.3 g of pure ruthenium oxide nanoparticles (pristine RuO ₂ nanoparticles) was dispersed in 30 ml of absolute ethanol, and then 30 ml of hexane and 3 ml of oleic acid (OA) were added.

Afterwards, the mixture was continuously stirred at room temperature for 15 hours to prepare ruthenium oxide (RuO ₂ -OA) nanoparticles surface-treated with oleic acid.

Figure 1 shows photographs taken immediately after and 15 hours after mixing an ethanol solution in which pure RuO ₂ nanoparticles were dispersed with hexane and oleic acid in the surface treatment process of nanoparticles.

Referring to Figure 1, it can be seen that the RuO ₂ nanoparticles dispersed in the lower ethanol layer completely moved to the upper hexane layer after stirring for 15 hours, confirming that the RuO ₂ nanoparticles were surface treated with oleic acid.

Spectroscopic confirmation of organic acid surface treatment:

To observe the organic acid ligands on the nanoparticles, Fourier transform IR spectroscopy (FT-IR spectrometer, Cary 630 FTIR, Agilent) was performed.

Figure 2 shows the FT-IR spectrum of RuO ₂ nanoparticles surface-treated with pristine RuO ₂ and OA. Referring to the results in Figure 2, it can be observed that the CH stretching band intensity increases rapidly after performing the surface treatment process with OA, and from this, OA conjugation on the nanoparticle surface can be confirmed.

Confirmation of dispersibility of surface-treated metal oxide nanoparticle dispersion:

The prepared RuO ₂ -OA nanoparticles were precipitated by adding ethanol and redispersed in octane at a concentration ranging from 0.1 to 20 mg/ml to prepare a RuO ₂ -OA nanoparticle dispersion.

Figure 3 shows photographs taken 24 hours after preparing RuO ₂ -OA nanoparticle dispersions at concentrations of 0.1, 0.2, 0.5, 1.0, 2.0, 5.0, 10.0, and 20.0 mg/ml. From Figure 3, it was confirmed that RuO ₂ -OA nanoparticles showed excellent dispersibility at all experimental concentrations.

Preparation Example 2: Preparation of transparent electrode using metal oxide nanoparticles surface treated with organic acid

A transparent electrode in the form of a thin film was manufactured using metal oxide nanoparticles surface-treated with organic acid.

The RuO ₂ -OA nanoparticle dispersion of Preparation Example 1 was spin-coated on an ITO-coated glass substrate (sheet resistance < 20 Ω cm ^-2 ). Specifically, 100 μl of RuO ₂ -OA NP dispersion (5.0 mg/ml, octane) was spin-coated at 3,000 rpm for 30 seconds, and then annealed at 200°C to remove organic acids, resulting in an electrode with a transmittance of 97%. was manufactured.

Manufacturing Example 3: Manufacturing a transparent supercapacitor using transparent electrodes

A supercapacitor device was manufactured using the transparent electrode manufactured by the method of Preparation Example 2.

A symmetrical supercapacitor device was fabricated by placing Surlyn ^TM tape, a polymer spacer, along the edge of the electrode and stacking two nanoparticle electrodes in a separated electrode form. The thickness of the tape (i.e., the height of the electrode space) was 120 μm, and heat treatment was performed at 100°C to seal the device.

A supercapacitor was manufactured by injecting 0.5M water-based H ₂ SO ₄ electrolyte (electrical conductivity 200 mS/cm) into the space through a pre-drilled small hole, and then blocking the hole with Surlyn polymer.

Experimental Example 1: Comparison of dispersibility of nanoparticles according to organic acid surface treatment

Figure 4 is a photograph of changes over time for pristine RuO ₂ nanoparticles dispersed in ethanol (a) and RuO ₂ -OA nanoparticles dispersed in octane (b). The concentration of the nanoparticle dispersion was adjusted to 10 mg/ml.

From Figure 4, it can be seen that RuO ₂ nanoparticles without surface treatment begin to precipitate after 1 hour, while RuO ₂ nanoparticles surface treated with organic acid are uniformly dispersed in a non-polar solvent (octane) for at least 24 hours. did.

From this, it was confirmed that the dispersibility of metal oxide nanoparticles was greatly improved by organic acid surface treatment.

Experimental Example 2: Comparison of homogeneity of nanoparticles according to organic acid surface treatment

Figure 5 shows TEM images of nanoparticles before (a) and after surface treatment (b). The morphology of the nanoparticle surface was observed using a high-resolution transmission electron microscope (HR-TEM, JEM-2100F, JEOL Ltd).

Referring to Figure 5, it can be seen that in the case of untreated RuO ₂ nanoparticles, it is difficult to specify the size due to non-uniform aggregation. On the other hand, RuO ₂ -OA nanoparticles were homogeneously distributed by OA chains on the surface, and the size was observed to be within the range of 1 to 2 nm.

Accordingly, it was confirmed that the aggregation problem of metal oxide nanoparticles can be solved by using organic acid surface treatment.

Experimental Example 3: Comparison of thin film morphologies according to organic acid surface treatment

A thin film prepared by spin coating a 10 mg/ml concentration of pristine RuO ₂ nanoparticle ethanol dispersion (a) and RuO ₂ -OA octane dispersion (b) using the method of Preparation Example 2 was examined using a field emission scanning electron microscope (FE-SEM). , JSM-7410F, JEOL Ltd), and the surface morphology image was obtained and shown in Figure 6.

As can be seen from Figure 6, in the case of pristine RuO ₂ nanoparticle coating, non-uniform surface morphology was observed, whereas RuO ₂ -OA nanoparticles showed a uniform surface morphology after spin coating on the ITO current collector layer.

Accordingly, it was confirmed that when organic acid surface treatment was used, metal oxide nanoparticles did not agglomerate and formed a uniform thin film.

Experimental Example 4: Comparison of permeability of thin films according to organic acid surface treatment

For each thin film in Experimental Example 3, the transmittance was measured at the point shown in FIG. 7 and the results are shown in (a) and (b) of FIG. 8, and the average transmittance in the visible light region was calculated and shown in FIG. 9. . US-Vis spectroscopy (Mega-800, SINCO) was used to measure transmittance.

Referring to the transmittance comparison results, a difference of about 10% in transmittance was observed for the pristine RuO ₂ nanoparticle coating film depending on the measurement point, but the RuO ₂ -OA nanoparticle coating film showed a difference of about 10% in the UV-vis spectrum measured at various points. You can see that there is almost no difference.

Comparing the transmittance measurement results with the morphology measurement results of Experimental Example 3, it was found that there was a difference in the transparency uniformity of the electrode due to the difference in surface morphology uniformity, and an electrode with uniform transmittance could be manufactured by organic acid surface treatment. I was able to confirm that it was there.

Experimental Example 5: Comparison of organic acid removal results according to heat treatment temperature

After manufacturing the RuO ₂ -OA nanoparticle coating film, heat treatment was performed at various temperatures, and removal of organic acids was confirmed through FT-IR and water contact angle measurements.

Figure 10 (a) shows the FT-IR spectrum at each heat treatment temperature, and it can be seen that the intensity of the C-H stretching band decreases as the heat treatment temperature increases. Specifically, the strength barely changed at a heat treatment temperature of 100°C, but decreased by about half at 150°C, and the C-H stretching peak was barely observed at 200°C.

Meanwhile, Figure 10 (b) shows the FT-IR spectrum of pristine RuO ₂ nanoparticles and RuO ₂ -OA nanoparticles. Comparing Figure 10 (a) and (b), the heat treatment temperature is 200°C. In this case, the spectrum corresponding to RuO ₂ was observed, confirming that the organic acid was removed after heat treatment at 200°C.

Figure 11 shows the water contact angle at each heat treatment temperature. When the oleic acid ligand, a long-chain fatty acid, is removed from the electrode surface, the surface becomes hydrophilic. Referring to Figure 11, the water contact angle was initially measured at 89.7°, but as the heat treatment temperature increased, the water contact angle gradually decreased, and after heat treatment at 200°C. It can be confirmed that it reaches 36.9°.

The FT-IR results and water contact angle according to the heat treatment temperature of the RuO ₂ -OA nanoparticle coating film are shown in Table 1 and are shown graphically in Figure 12.

Heat treatment temperature (℃) Relative C-H intensity (%) Water contact angle (°) room temperature (RT) 100 89.7 100 91.5 81.9 150 56.5 55.7 200 3.4 36.9

From the results in Table 1 and Figure 12, it was confirmed that the change in contact angle according to heat treatment temperature was consistent with the FT-IR results. From this, it was clearly observed that the organic acid was removed by heat treatment, and it was confirmed that almost all of the organic acid was removed after heat treatment at 200°C.

Experimental Example 6: Comparative observation of electrode morphology according to heat treatment temperature

Figure 13 shows a surface FE-SEM image of the RuO ₂ -OA coating film after heat treatment at each temperature for 1 hour, and Figure 14 shows an X-ray diffraction pattern after heat treatment at 200°C for 1 hour.

Referring to the morphology and crystal analysis results of Figures 13 and 14, it was confirmed that the heat treatment temperature had little effect on the surface morphology and crystal phase.

Experimental Example 7: Comparison of electrode capacitance according to heat treatment temperature

When removing the organic acid, the difference in capacitance of the electrode according to the heat treatment temperature was measured and the results were compared.

Electrodes with a visible light transmittance ( T _vis ) of 90% were heat treated at 100°C, 150°C, 200°C, 250°C, and 300°C, respectively, and cyclic voltammetry (CV) analysis was performed at a scanning speed of 100 mV/s. carried out. CV analysis is This was performed using a cyclic voltammeter (ZIVE SP2, WonATech) under room temperature conditions in 0.5M aqueous H ₂ SO ₄ electrolyte, using a 3-electrode device including a platinum plate and an Ag/AgCl electrode (3M KCl) as the counter and reference electrodes, respectively. The system was used.

In the case of electrodes without heat treatment, the deposited RuO ₂ film fell off the ITO current collector during CV measurement, making capacitance measurement impossible.

Figure 15 shows the CV contour results according to each heat treatment temperature, and the area capacitance ( C _A ) was calculated using the equation below and shown in Figure 16 and Table 2.

In the above formula, J (mA/cm ² ) is the area current, Δ V (V) is the potential window, and d V /d t (mV/s) is the scan rate. do.

Heat treatment temperature (℃) Area capacitance ( C _A , mF/cm ² ) 100 0.51 150 1.79 200 2.34 250 1.23 300 1.04

Referring to the C _A measurement results, C _A increased significantly as the heat treatment temperature increased up to 200°C, but as the heat treatment temperature was further increased to 250°C and 300°C, it was confirmed that C _A decreased.

From this, it was confirmed that the heat treatment temperature when removing organic acids greatly affects the capacitance, and that heat treatment at 200°C is most desirable to manufacture high-performance supercapacitor electrodes.

Experimental Example 8: Comparison of transmittance according to concentration of nanoparticle dispersion and number of spin coating cycles

Electrodes were manufactured by adjusting the concentration of the nanoparticle dispersion and the number of spin coating cycles, and the transparency of each electrode was compared.

Using RuO ₂ -OA nanoparticle dispersions with concentrations of 2.5, 5, 7.5, 10, 15, and 20 mg/ml, electrodes were prepared by performing spin coating once (single coating) or twice (double coating), and each The visible light transmittance ( T _vis ) of the electrode is shown in Figure 17. In Figure 17, (a) shows the transmittance of the once-coated electrode, and (b) shows the transmittance of the twice-coated electrode.

Based on the transmittance results in FIG. 17, the results of comparing the average transmittance for each concentration of each electrode are shown in FIG. 18.

As can be seen in Figure 18, the average transmittance in the visible light wavelength region was inversely proportional to the concentration of the dispersion, and the transmittance when a dispersion of a certain concentration was coated once and the transmittance when a dispersion of half the concentration was coated twice The transmittance was almost the same.

For example, 5.0mg/ml The transmittance of the electrode coated once with the dispersion was 97.5%, which was almost the same as the transmittance of 97.1% for the electrode coated twice with the 2.5 mg/ml dispersion. Also, 20mg/ml Electrode coated with dispersion once and 10mg/ml The transmittance of the electrode coated with the dispersion twice was 89.0% and 88.6%, respectively, and it was confirmed that the above trend appears even at high concentrations.

Figure 19 shows a graph of the transmittance of the electrode and a photograph of the electrode under each transmittance condition. Referring to Figure 19, it can be seen that the electrode is optically transparent.

Figure 20 is a graph showing the measured value of the RuO ₂ film thickness as a function of absorbance, and it was confirmed that the absorbance increased (transmittance decreased) as the thickness increased.

Since it is difficult to practically measure the thickness when the thickness is 10 nm or less, the thickness was derived using an extrapolation method based on the graph of the thickness-permeability results. As a result, it was confirmed that the film thickness was about 3.3 and 7.2 nm for electrodes with visible light transmittance of 97.1 and 93.9%, and that it was possible to form a thin film of 10 nm or less using the present invention.

The thinner the electrode thickness, the lower the electrical resistance, and it was found that using the present invention is advantageous in terms of improving the electrical characteristics of a supercapacitor because it is possible to form an ultra-thin electrode.

Experimental Example 9: Comparison of electrode capacitance according to dispersion concentration and number of coating cycles

For each electrode in Experimental Example 8, in order to compare the physical properties of electrodes with similar transmittances ( T _vis ), CV measurements were performed under conditions of a scanning speed of 100 mV/s, and area capacitance ( C _A ) was calculated, and the results are shown in FIG. 21 indicated.

Referring to Figure 21, it can be seen that the two electrodes with similar transmittances have almost no difference in the shape of the CV contour and area capacitance. As a result of measurements at all concentrations, the difference in T _vis and C _A values for the electrode coated twice and the electrode coated once at twice the concentration was only 0.5% and 4%, respectively.

Accordingly, it was confirmed that using the method of the present invention, the performance of the electrode can be easily adjusted by adjusting the concentration of the nanoparticle dispersion and the number of coatings.

Experimental Example 10: Comparison of electrostatic capacity characteristics of electrodes

For each RuO ₂ electrode in Experimental Example 8, electrochemical performance was measured using CV in the range of 0.0 to 0.9V.

The CV contour measured at a scan rate of 100 mV/s for electrodes with a T _vis range of 79.1 to 97.1% is shown in Figure 22. Referring to Figure 22, the CV contour showed an almost rectangular and symmetrical shape.

From this, it was confirmed that the electrode manufactured according to the present invention had excellent electrostatic capacity and excellent reversibility in redox reactions.

Figure 23 shows the area capacitance of the RuO ₂ nanoparticle transparent electrode manufactured according to the present invention compared with the transparent electrode of other conventional studies. The electrode manufactured using the present invention has a similar transmittance to the electrodes of the prior art. It can be seen that the capacitance is superior compared to .

Additionally, Figure 24 shows C _A of the electrode according to transparency as a function of scanning speed.

Referring to the results in FIG. 24, in the case of an electrode with a transmittance of 97.1%, C _A was 0.85 at a scanning speed of 10 mV/s, and C _A decreased to 0.69 at 1,000 mV/s. In other words, even at a high scanning speed of 1,000 mV/s, the C _A retention rate was confirmed to be very high at the level of 81.2%. C _A gradually decreased as the transmittance decreased, and the retention rate was calculated to be 67.2% for an electrode with a transmittance of 79.1%.

According to these experimental results, it was confirmed that the RuO ₂ nanoparticle transparent electrode of the present invention maintains a significant ratio of C _A even at high scanning speeds, and has a very fast voltammetric response.

Experimental Example 11: Quantitative analysis using deconvolution method

Capacitive elements were quantitatively separated using a deconvolution method for RuO ₂ transparent electrodes with visible light transmittance ( T _vis ) of 97.1% and 79.1%. Through this, excellent area capacitance and high reaction speed were confirmed.

According to the equation below, the current measured under specific voltage conditions was separated into two elements: a surface capacitive element ( k ₁ v ) and a diffusion-controlled insertion element ( k ₂ v ).

In the above equation, i ( V ) is the current, v is the scanning speed, and k ₁ and k ₂ are constants.

Figure 25 shows the deconvolution results, where the contour (shaded area) of the k ₁ v plot represents the surface capacitive element, and the other areas correspond to the insertion element. Figures 25 (a) to (c) show the deconvolution results for the electrode with T _vis 97.1%, and (d) to (f) show the deconvolution results for the electrode with T _vis 79.1%.

Referring to FIG. 25, it was confirmed that the surface capacitive element has a virtually independent relationship with the scanning speed, while the insertion element is greatly affected by the scanning speed. In addition, it can be seen that the contribution of the surface capacitive element of the RuO ₂ nanoparticle transparent electrode manufactured according to the present invention is significantly larger than that of the conventional pseudocapacitor, and the dependence on the scanning speed is low.

These results are comparable to carbon-based electric double layer capacitors (EDLC), confirming that the specific surface area increases and efficient contact with the electrolyte due to the small size and excellent dispersibility of RuO ₂ nanoparticles.

Experimental Example 12: Symmetric 2-electrode cell manufacturing and physical property measurement

A highly transparent energy storage device was manufactured by assembling a symmetrical two-electrode cell using the method of Preparation Example 3.

Specifically, a separator-free device with an active area of 1.5 Х 1.2 cm ² was manufactured by injecting electrolyte into the space between two electrodes separated by a polymer (Surlyn film) spacer. The visible light transmittance ( T _vis ) of each electrode used was 95.8%, and the area capacitance ( C _A ) was 1.1 mF/cm ² at a scanning speed of 10 mV/s.

A photograph of the manufactured device is shown in Figure 26, and a transmittance graph in the visible light region is shown in Figure 27. As can be seen from Figures 26 and 27, the manufactured device showed high transparency with an average T _vis of 92.3%.

Additionally, CV measurements were performed in the voltage range of -0.9 to 0.9V and the results are shown in Figure 28. Referring to Figure 28, the CV curve shows a nearly symmetrical and rectangular shape, confirming that the device has excellent reversibility.

Figure 29 shows the galvanostatic charge/discharge (GCD) curve of the device measured at various current densities, showing the ideal triangular shape.

Figure 30 shows the capacitance retention of the device as a function of scan speed. When the scanning speed was high, the potential response of the device was somewhat lower than that of a single electrode, but under the scanning speed condition of 1,000 mV/s, a retention rate of 71.7% compared to 10 mV/s was confirmed.

Figure 31 shows the results of electrochemical impedance spectroscopy (EIS) measurement. The Z' and Z'' values obtained from the Nyquist plot in Figure 31 represent the real and imaginary parts of the impedance, respectively. The charge transfer resistance ( R _ct ) obtained from the straight region of the circular arc in the high frequency region was measured to be 2.7Ω.

The device using the present invention was measured to have a very small R _ct value compared to the conventional pseudocapacitor, and from this, it was confirmed that the charge transfer characteristics were very excellent. In addition, the slope of the straight line is inversely proportional to diffusion resistance ( R _d ), and it can be seen from the steep straight line in the low-frequency region that the diffusion resistance of the device is low.

Figure 32 shows the capacitance retention rate according to the number of GCD cycles at a current density of 0.05 mA/cm ² . Referring to FIG. 32, the capacitance retention rate after 5,000 cycles was calculated to be 93.5% of the initial value, confirming that cycle stability was very excellent.

Experimental Example 13: Cell manufacturing and physical property measurement using spray coating

An energy storage device cell was manufactured using electrodes manufactured using spray coating instead of spin coating when coating the nanoparticle dispersion.

Specifically, a dispersion solution containing RuO ₂ -OA nanoparticles dispersed in octane at a concentration of 1.0 mg/ml was sprayed on a 5 cm Х 5 cm ITO/glass substrate and then heat treated at 200°C. During spray coating, the nozzle was placed 15cm away from the substrate, and a spray gun system (spray gun system, Iwata, Eclipse HP-CS) was used for spraying.

By assembling two spray-coated RuO ₂ nanoparticle electrodes, a large-area full-cell device was manufactured. A photograph of a large-area full-cell produced by spray coating is shown in Figure 33. Figure 34 shows the transmittance of the device manufactured when an electrode with a visible light transmittance ( T _vis ) of 92.1% was used, and the visible light transmittance of the device was calculated to be 80.6%.

For the large-area device, the results of CV measurements performed at a scanning speed of 10 mV/s are shown in FIG. 35. As a result, the maximum areal capacitance was measured to be 0.83mF/cm ² , and the shape of the rectangular and symmetrical CV curve was confirmed. From this, it was confirmed that excellent capacitance characteristics and reversibility were maintained even in large-area devices using spray coating.

Figure 36 is a graph showing area capacitance according to scanning speed. As can be seen in Figure 35, excellent results were obtained with a capacitance retention rate of 75.8% at a high scanning speed of 1,000 mV/s. From this, it was confirmed that rapid response is possible at high scanning speeds even in large-area devices.

Although some implementation forms of the present invention have been described above, the present invention is not limited to the above-described implementation forms, but can be implemented with modifications and variations without departing from the gist of the present invention, and such modifications and variations can be made. This added form should also be understood as belonging to the technical idea of the present invention.

Claims (20)

Coating a dispersion of metal oxide nanoparticles surface-treated with an organic acid on a substrate; and
Forming a capacitive material layer by heat treating the dispersion coating at 120 to 300° C. to remove organic acids from the surface of the nanoparticles.
Method for manufacturing an electrode for a supercapacitor, including.
According to claim 1,
A method of manufacturing an electrode for a supercapacitor, wherein the metal oxide is an oxide of a metal selected from the group consisting of Ru, Mn, Co, Ti, Zn, and Ni.
According to claim 1,
A method of manufacturing an electrode for a supercapacitor, wherein the organic acid has 10 or more carbon atoms.
According to claim 1,
Super, wherein the substrate is a transparent substrate coated with a current collector material selected from the group consisting of indium tin oxide (ITO), fluorine-doped tin oxide (FTO), indium zinc oxide (IZO), and aluminum-doped zinc oxide (AZO). Method for manufacturing electrodes for capacitors.
According to claim 1,
A method of manufacturing an electrode for a supercapacitor, wherein the concentration of the dispersion is 0.1 to 20 mg/ml.
According to claim 1,
A method of manufacturing an electrode for a supercapacitor, wherein the coating of the dispersion is performed by spin coating, spray coating, doctor blade, or bar coating.
delete According to claim 1,
A method of manufacturing an electrode for a supercapacitor, wherein the capacitive material layer has a thickness of 1 to 100 nm.
According to claim 1,
A method of manufacturing an electrode for a supercapacitor, wherein the metal oxide nanoparticles surface-treated with the organic acid are manufactured by reacting pristine metal oxide nanoparticles with an organic acid.
According to clause 9,
A method of manufacturing an electrode for a supercapacitor, wherein the pure metal oxide nanoparticles have an average particle diameter of 0.5 to 5 nm.
According to clause 9,
A method of manufacturing an electrode for a supercapacitor, wherein the reaction between the pure metal oxide nanoparticles and the organic acid is performed at a temperature of 10 to 50 ° C.
According to clause 9,
A method of manufacturing an electrode for a supercapacitor, wherein the reaction between the pure metal oxide nanoparticles and the organic acid is performed under conditions where a polar solvent and a non-polar solvent coexist.
According to claim 12,
A method of manufacturing an electrode for a supercapacitor, wherein the polar solvent includes at least one solvent selected from the group consisting of water, ethanol, acetone, ammonia, and acetic acid.
According to claim 12,
A method of manufacturing an electrode for a supercapacitor, wherein the non-polar solvent includes one or more solvents selected from the group consisting of hexane, pentane, heptane, benzene, toluene, xylene, and cyclohexane.
According to clause 9,
A method of manufacturing an electrode for a supercapacitor, wherein the pure metal oxide nanoparticles are produced by reaction of a metal halide and a basic additive.
According to claim 15,
A method of manufacturing an electrode for a supercapacitor, wherein the basic additive includes at least one selected from the group consisting of LiOH, NaOH, and NH ₄ OH.
An electrode for a supercapacitor manufactured by the method of any one of claims 1 to 6 and 8 to 16.
According to claim 17,
An electrode for a supercapacitor, wherein the electrode has a visible light transmittance of 70% or more.
A transparent supercapacitor comprising the supercapacitor electrode and electrolyte of claim 17.
According to claim 19,
A transparent supercapacitor wherein the transparent supercapacitor further includes a separator.