KR20100045097A - Manufacturing method of lithum tungsten oxide coating material and manufacturing method of electrochromic device - Google Patents

Abstract

PURPOSE: A manufacturing method of a lithium tungsten oxide coating material is provided to obtain a lithium tungsten oxide thin film with improved coloring efficiency, response speed, and charge density. CONSTITUTION: A manufacturing method of a lithium tungsten oxide coating material comprises the following steps: forming a transparent tungsten solution by dissolving tungstic acid powder or tungsten metal powder in hydrogen peroxide liquid; forming peroxo tungstic acid with a transparent orange color marked with the chemical formula WO3xH2O2xyH2O(0.05<=x<=1.0, 0.5<=y<=10) by vaporizing water and the hydrogen peroxide liquid from the tungsten solution; forming a tungsten oxide solution by dissolving the peroxo tungstic acid in an organic solvent; forming a lithium source solution; and forming lithium tungsten oxide by mixing the lithium source solution and the tungsten oxide solution.

Description

Manufacturing method of lithium tungsten oxide coating material and manufacturing method of electrochromic device using same {Manufacturing method of lithum tungsten oxide coating material and manufacturing method of electrochromic device}

The present invention relates to a method for manufacturing a lithium tungsten oxide coating material and a method for manufacturing an electrochromic device using the same, and more particularly, does not require a precharge process, and lithium ions can be uniformly distributed throughout the entire lithium tungsten oxide thin film. The present invention relates to a method of manufacturing a lithium tungsten oxide coating material having excellent coloring efficiency, response speed, and charge density characteristics when forming a lithium tungsten oxide thin film, and a method of manufacturing an electrochromic device using the same.

In general, electrochromism means that when an external current is applied to a substance, ions and electrons enter and exit by electrochemical reduction reaction (anode reaction) and oxidation reaction (cathode reaction). It refers to a phenomenon in which the color is reversibly changed, that is, colored when the electric field is applied, and discolored when the opposite electric field is applied.

The electrochromic reaction phenomenon is applied to manufacture display devices, smart glasses, and the like. As the electrochromic material, vanadium pentaoxide, cobalt oxide, tungsten oxide, tungsten molybdenum oxide, fluoride glass, etc. are mainly used. Electrochromic materials (electrochromic materials) are characterized by the color change by the applied voltage, the electrochromic materials are returned to the original color when the applied voltage disappears or the polarity is reversed.

The most widely used electrolytic material so far is tungsten oxide (WO ₃ ). The tungsten oxide has high ion mobility and is colored blue by absorbing light in the visible region.

Electrochromic thin films such as tungsten oxide undergo a reversible color change by the application of an electric field or current. Such a color change can be divided into a positive electrode electrochromic material that changes positively and a negative electrode electrochromic material that changes negatively. Tungsten oxide is a typical anode electrochromic material. Tungsten oxide becomes blue tungsten oxide or lithium tungsten oxide when a negative electric field is applied in an electrolyte solution containing protons or lithium ions. This is called reduction coloring and such an electrochromic material is called an anode electrochromic material. In contrast, nickel oxide or cobalt nickel is colored when a positive electric field is applied. This is called oxidation coloring and is called a cathode electrochromic material.

And the method of forming a tungsten oxide thin film is the most typical method is a coating method using a vacuum deposition equipment, such as deposition or sputtering, which can be called a physical coating method. In addition, a chemical vapor deposition (CVD) method of reacting chloride at a high temperature may be considered. A uniform thin film may be obtained by such a coating method, and a coating process may be performed at a relatively low temperature, but a very expensive coating equipment should be used. There is a disadvantage.

U.S. Patent No. 5,525,264 discloses oxalic acid, malonic acid, glutaric acid, apicic acid, ethylenedimitateacetic acid, glycerol, formamide, etc. in order to increase the thickness of the tungsten oxide thin film and prevent cracking of the thin film. It is suggested that the reaction rate is faster when coloring and decolorizing when a small amount is added within 10%.

It is easy to dissolve tungsten powder or tungstic acid in hydrogen peroxide water, but water contained in hydrogen peroxide or unreacted hydrogen peroxide causes problems in coating tungsten thin films. For example, when water is present, a glass substrate coated with a transparent transparent conductive film has a problem in that it is difficult to form a thin film by forming water droplets without coating the coating solution on the substrate due to hydrophilic properties.

Therefore, it is necessary to remove water or unreacted hydrogen peroxide. In the case of US Patent No. 5,525,264, alcohol is first added and then reacted at 80 ° C. to induce the milky white reactant to be transparent orange, but this reaction is easy. There is a problem that does not occur and these reactants are insoluble in ordinary solvents. In addition, the synthesis of acetylated peroxungstic tungstic acid is carried out by adding acetic acid to react, reflux and vacuum drying and filtering. Synthesis method described in U.S. Patent No. 5,525,264 varies depending on the melting temperature and boiling point of the additive, but below 200 ° C, organic matters are decomposed and do not fly away.

In addition, when synthesizing the tungsten oxide coating solution, the transparent conductive film is coated in order to dissolve the tungsten metal powder or tungstic acid in hydrogen peroxide solution and then obtain a uniform thin film by a coating method such as spin coating, dip coating, and spray coating. Excess water and hydrogen peroxide must be removed to form a film on the substrate glass. If the reaction temperature is not controlled when the excess water and hydrogen peroxide are removed, a compound in which water molecules are bound to tungsten oxide is produced. It does not dissolve in a solvent such as has a problem that is not suitable as a coating solution.

In addition, the Republic of Korea Patent Publication No. 10-0806694 filed and registered by the present applicant proposes a manufacturing method of the electrochromic coating material and its coating method. Patent No. 10-0806694 discloses a method of dissolving tungsten metal powder or tungstic acid powder in 30% hydrogen peroxide water and then removing excess hydrogen peroxide water and water. The present invention relates to a method of synthesizing peroxungic acid by reacting and diluting it in ethanol to synthesize a coating solution and coating the solution using dip coating or spin coating.

However, the method of Korean Patent Publication No. 10-0806694 requires very careful control of the reaction temperature in order to remove excess hydrogen peroxide water and water, and if the reaction temperature is not controlled, tungsten oxide hydrate is likely to precipitate and precipitate. There are disadvantages. Therefore, the reaction temperature must be precisely controlled, but the disadvantage is that the reaction time takes more than 20 hours when preparing more than 1 liter (ℓ). In addition, the long synthesis time of the peroxrogen tungstic acid solution is not easy to control the temperature, there is a high possibility that the tungsten oxide hydrate precipitates without dissolving in the organic solvent, and controlling the chemical composition ratio of the resulting peroxungstic acid It is not easy and has the disadvantage of low synthesis yield of peroxungstic tungstic acid.

In order to solve this problem, the present inventors reduce perox tungsten oxide time to 1/6 by the method of evaporating excess hydrogen peroxide and water while bubbling or rotating concentration with nitrogen gas. The method was developed. However, the amorphous tungsten oxide thin film coated with the peroxo tungsten oxide synthesized by this method usually has about 20 to 30% of pores. In order to make an electrochromic device, a process of injecting ions into the thin film by activation, that is, applying a voltage, is performed. Should go through. This process is called pre-charge, through which proton ions or lithium ions are implanted into the tungsten oxide thin film to form hydrogen tungsten oxide or lithium tungsten oxide, and the electrochromic device easily receives ions by application of voltage. You can come and go. However, this precharge process has difficulty in controlling the process conditions, it is difficult to inject homogeneous ions through the entire thin film, so that the reliability is low and the reproducibility is not good. Therefore, there is a need for a method for eliminating this precharge process and making the import and export of ions easier.

The technical problem to be achieved by the present invention does not require a precharge process, the lithium ion can be uniformly distributed throughout the lithium tungsten oxide thin film is excellent in reliability and reproducibility, the coloring efficiency in the case of forming a lithium tungsten oxide thin film, A method of manufacturing a lithium tungsten oxide coating material having excellent response speed and charge density characteristics, and a method of manufacturing an electrochromic device using the same.

The present invention comprises the steps of (a) dissolving the tungsten (W) metal powder or tungstic acid (H ₂ WO ₄ ) powder in hydrogen peroxide water to form a transparent tungsten solution, and (b) a certain amount of water contained in the tungsten solution Hydrogen peroxide and water were evaporated while heating at a temperature of 40-90 ° C. to remove hydrogen peroxide, thereby providing a transparent chemical having the formula WO ₃ · xH ₂ O ₂ · yH ₂ O (0.05 ≦ x ≦ 1.0, 0.5 ≦ y ≦ 10) Forming an orange perfluoro tungstic acid, (c) dissolving the perox tungstic acid in an organic solvent to form a tungsten oxide solution, and (d) mixing well when mixed with the tungsten oxide solution. Forming a lithium source solution in which no separation of the solution occurs and no precipitation of lithium salts, lithium hydroxide and lithium tungsten occurs, and (e) a lithium tungsten oxide (Li _x WO) by mixing the lithium source solution and the tungsten oxide solution. ₃ ) It includes forming, the lithium tungsten oxide provides a method for producing a lithium tungsten oxide coating material in which the molar ratio of lithium ions to tungsten ranges from 0.1 to 1.

The lithium source solution may be a solution in which a lithium compound or a lithium salt is dissolved in an organic solvent, an alkoxide or lithium amide solution containing lithium.

The lithium compound or lithium salt is lithium fluoride (LiF), lithium chloride (LiCl), lithium hydroxide (LiOH), lithium carboxylate (LiCOOH), lithium nitrate (LiNO ₃ ), lithium sulfate (Li ₂ SO ₄ ), lithium At least one material selected from oxychloride (LiClO ₄ ) and lithium pentamethylcyclopentadienyl may be.

The organic solvent for dissolving the lithium compound or lithium salt may be at least one solvent selected from polycarbonate, tetrahydrofuran, alcohol and water.

In the step (b), hydrogen peroxide and water are evaporated while bubbling the tungsten solution by injecting nitrogen (N ₂ ) gas at 0.1 to 100 l / min while heating at a temperature of 40 to 90 ° C. to remove water and hydrogen peroxide. To form the peroxungic tungstic acid.

After evaporating the hydrogen peroxide and water while bubbling the tungsten solution, the method may further include distilling under reduced pressure at a temperature of 40 ° C. to 90 ° C. using a rotary concentrator to form a solid peroxungous tungstic acid.

The step (b) may be performed by distillation under reduced pressure using a rotary concentrator while heating at a temperature of 40 ~ 90 ℃ to remove water and hydrogen peroxide to form a solid peroxo tungstic acid.

In the step (c), the tungsten oxide is mixed with at least one organic solvent selected from methanol, ethanol, propanol, isopropyl alcohol and 2-methoxyethanol to have a concentration of 0.1 to 1 M to form a tungsten oxide solution. It can be made to the step.

In addition, the present invention is coated on a glass substrate coated with a transparent conductive film to a thickness of 50nm ~ 1㎛ using a dip coating, spin coating, bar coating or slot die coating to the lithium tungsten oxide coating solution, 100 ~ 500 ℃ It provides a method of manufacturing an electrochromic device to form an amorphous lithium tungsten oxide thin film or crystalline lithium tungsten oxide thin film by heat treatment at a temperature of.

The lithium tungsten oxide thin film is used as an electrochromic electrode, and CeO ₂ TiO ₂ , NiOOH, or Flushian blue thin film is used as a counter electrode, and an electrochromic device is formed by filling and sealing an electrolyte between the electrochromic electrode and the counter electrode. Can be produced.

According to the present invention, when manufacturing an electrochromic device, a tungsten oxide thin film is formed by coating a tungsten oxide solution on a substrate coated with a transparent conductive film, and a precharge process is required to inject ions into the tungsten oxide thin film by applying a voltage. The process is simple and the manufacturing time can be shortened.

In addition, a tungsten oxide solution and a lithium source solution are mixed to synthesize a homogeneous lithium tungsten oxide, and the lithium tungsten oxide coating solution is coated on a substrate coated with a transparent conductive film to form a lithium tungsten oxide thin film, thereby uniformly injecting lithium ions. Since the effect can be obtained, it is possible to replace the precharge process, obtain an electrochromic device having excellent reliability, and have an advantage of excellent reproducibility.

In addition, the lithium tungsten oxide thin film prepared according to the present invention has an advantage of excellent coloring efficiency, response speed, charge density characteristics, and the like.

In addition, the buffer rokso in forming the tungstic acid compound, a nitrogen (N ₂₎ by bubbling using a gas can shorten the time for removing the hydrogen peroxide and water, to ensure the uniformity of the synthesized spread rokso tungstate compound There are advantages to it.

In addition, when the solvent is evaporated in vacuo using a rotary concentrator, cooled, and concentrated, a solid peroxotungstic acid which is very stable can be obtained by reaction of about the same reaction time as N ₂ bubbling, and solid peroxungon tungsten is obtained. Acid has the advantage of being easily soluble in organic solvents such as ethanol and easily obtaining a tungsten oxide solution.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the following embodiments are provided to those skilled in the art to fully understand the present invention, and may be modified in various forms, and the scope of the present invention is limited to the embodiments described below. It doesn't happen.

It describes a method for producing a lithium tungsten oxide coating material according to a preferred embodiment of the present invention.

In order to prepare a lithium tungsten oxide coating material, first, tungsten (W) metal powder or tungstic acid (H ₂ WO ₄ ) powder is dissolved in hydrogen peroxide so that the concentration is 0.1 to 1 M. It is preferable to dissolve while cooling because oxygen and hydrogen gas are generated while a rapid exothermic reaction occurs in the dissolution process. When the tungsten (W) metal powder or tungstic acid (H ₂ WO ₄ ) powder is completely dissolved in hydrogen peroxide solution, a transparent tungsten solution is obtained.

The tungsten solution dissolved in hydrogen peroxide solution is heated to 40-90 ° C. to remove water and hydrogen peroxide to form peroxo tungstic acid (PTA) (WO ₃ · xH ₂ O ₂ · yH ₂ O).

In general, perox tungstic acid is known as a compound having a chemical formula of WO ₃ · xH ₂ O ₂ · yH ₂ O, where x and y values are known as 0.05 ≦ x ≦ 1.0 and 0.5 ≦ y ≦ 10. The x value, the bound number of hydrogen peroxide, can be obtained by iodometry, and the y value can be obtained through thermogravimetric analysis (TGA).

A sol synthesized with tungsten (W) metal powder or tungstic acid (H ₂ WO ₄ ) powder using hydrogen peroxide is synthesized with yellow and orange solutions according to the synthesis process. In the case of yellow, colloidal particles are formed in the solution. It becomes opaque and particles are precipitated over time. This solution is not preferable because of poor coating uniformity. In the case of orange color, uniform and transparent solution is synthesized. And the solution and the coating film according to the change over time can be said to be the preferred solution in terms of stability.

Tungsten solution dissolved in hydrogen peroxide solution at 40-90 ° C. with peroxo tungstic by using nitrogen (N ₂ ) bubbling, rotary evaporate or a mixture thereof acid; PTA) (WO ₃ · xH ₂ O ₂ · yH ₂ O). If the temperature is too high in the process of removing hydrogen peroxide and water, yellow precipitates or white precipitates may be produced. These products are tungsten oxide hydrates, which are insoluble in alcohol, and thus the temperature is about 40 ~ 90 ℃. It is desirable to maintain.

The peroxungic tungstic acid is dissolved in an organic solvent such as ethanol, isopropyl alcohol, or 2-methoxyethanol to have a concentration of 0.1 to 1 M to synthesize a transparent and orange tungsten oxide solution.

A lithium tungsten oxide coating solution was synthesized by mixing a lithium source solution containing lithium into a transparent orange tungsten oxide solution.

Hereinafter, a method of synthesizing a lithium tungsten oxide coating solution will be described in more detail.

Hydrogen peroxide and water are evaporated while the tungsten solution dissolved in hydrogen peroxide solution is heated at a temperature of about 40 to 90 ° C. to form peroxo tungstic acid (PTA) (WO ₃ · xH ₂ O ₂ · yH ₂ O). do. It is desirable to maintain the reaction until 20% by volume of solution remains. If the temperature is too high in the process of removing hydrogen peroxide and water, yellow precipitates or white precipitates may be produced. These products are tungsten oxide hydrates, which are insoluble in alcohol, and thus the temperature is about 40 ~ 90 ℃. It is desirable to maintain.

In addition, in order to remove excess water and hydrogen peroxide contained in the tungsten solution, while injecting nitrogen (N ₂ ) gas at a rate of 0.1 to 100 l / min while heating at a temperature of about 40 to 90 ℃ bubbling a transparent tungsten solution It is also possible to use a method of evaporating hydrogen peroxide and water by bubbling. It is desirable to maintain the reaction until 20% by volume of solution remains. In the case of bubbling using nitrogen gas, the time for removing hydrogen peroxide and water is only about 1/6 as compared to the method for removing only by heating, and it is possible to shorten the synthesis time of peroxungic acid. There is an advantage that can ensure the uniformity of the peroxo tungstic acid solution. When evaporated while bubbling with N ₂ , it has the advantage of obtaining the desired peroxungstic acid in a reaction of about 3 hours, and because the reaction time is short, the temperature control is easy and the possibility of generating tungsten oxide hydrate is very low. Since the probability of not obtaining peroxo tungstic acid decreases, the yield of synthesizing peroxo tungstic acid increases.

In addition, in order to remove excess water and hydrogen peroxide contained in the transparent tungsten solution, the tungsten solution dissolved in hydrogen peroxide solution was distilled under reduced pressure while rotating at 40 to 90 ° C. using a rotary evaporator to produce orange peroxotung tungsten. Acids can also be synthesized. When the solvent is evaporated in a vacuum using a rotary condenser, cooled, and concentrated, a peroxotungstic acid can be obtained by reacting with a reaction time (3-4 hours) which is almost the same as N ₂ bubbling, in which case a very stable solid phase Compounds can be obtained, which can be dissolved in an organic solvent such as ethanol and used as a coating solution.

In addition, in order to remove the excess water and hydrogen peroxide contained in the transparent tungsten solution while injecting nitrogen (N ₂ ) gas at a rate of 0.1 to 100 l / min while heating at a temperature of about 40 ~ 90 ℃ bubble of a transparent tungsten solution It is also possible to synthesize orange peroxrogen tungstic acid by bubbling and evaporating a certain amount of hydrogen peroxide and water, and then evaporating and cooling the solvent under vacuum while concentrating by rotating at 40 to 90 ° C. using a rotary concentrator. have.

Peroxungstic tungstic acid has the form of WO ₃ · xH ₂ O ₂ · yH ₂ O, wherein controlling the contents of x and y has the advantage of being easier when using N ₂ bubbling or rotary concentrator.

The reaction product thus obtained is an orange peroxo tungstic acid compound. The addition of an organic solvent such as methanol, ethanol, propanol, isopropyl alcohol, 2-methoxy ethanol and the like to the peroxotungstic acid synthesizes a transparent orange tungsten oxide solution. It is preferable to form a tungsten oxide solution by dissolving it in the said organic solvent so that a perox tungstic acid will have a density | concentration of about 0.1-1 M.

A lithium tungsten oxide coating solution was synthesized by mixing a lithium source solution containing lithium into a transparent orange tungsten oxide solution. At this time, it is preferable to mix so that the quantity of lithium (Li) ion may be 0.1-1 mole ratio with respect to tungsten (W). If the amount of lithium (Li) ions is too large compared to tungsten (W), precipitation of lithium salts, lithium hydroxide or lithium tungsten compounds may occur, and the amount of lithium (Li) ions is too small compared to tungsten (W). In this case, when the electrochromic device is manufactured, the number of ions moving with the application of the voltage is small, so that an electrochromic device having satisfactory performance cannot be expected. When the molar ratio of lithium (Li) ions to tungsten (W) is about 0.1 to 1, the lithium salt, lithium hydroxide, or lithium tungsten compound does not precipitate, but moves with application of voltage when manufactured as an electrochromic device. Electrochromic devices with satisfactory performance can be expected because the number of ions is appropriate, and even when a thin film is formed by coating a lithium tungsten oxide coating solution, the transparent conductive film can be adhered well to the coated glass substrate.

The lithium source solution may be a solution in which a lithium compound or a lithium salt is dissolved in an organic solvent, a lithium amide-based solution such as alkoxide or lithium dimethylamide containing lithium. The alkoxide may be lithium butoxide, lithium ethoxide, lithium methoxide and the like. The lithium compound or lithium salt is lithium fluoride (LiF), lithium chloride (LiCl), lithium hydroxide (LiOH), lithium carboxylate (LiCOOH), lithium nitrate (LiNO ₃ ), lithium sulfate (Li ₂ SO ₄ ), lithium Lithium-containing compounds or salts such as oxychloride (LiClO ₄ ), lithium pentamethylcyclopentadienyl and the like. When the tungsten oxide solution and the lithium source solution are mixed, the organic solvent dissolving the lithium compound or the lithium salt is well mixed with each other, and precipitation or separation of the solution does not occur, and precipitation of lithium salt, lithium hydroxide, or lithium tungsten does not occur. Solvents such as polycarbonate, tetrahydrofuran (THF), alcohols and water are used.

Hereinafter, a method of forming the tungsten oxide thin film will be described.

Lithium tungsten oxide coating solution was coated on a transparent conductive film-coated substrate (eg, a glass substrate) to a thickness of 50 nm to 1 μm using a method such as dip coating, spin coating, bar coating, or slot die coating. Heat treatment at a temperature of 500 ℃ to form an amorphous lithium tungsten oxide thin film or crystalline lithium tungsten oxide thin film.

A case of forming a lithium tungsten oxide thin film using dip coating will be described as an example. Dipping a glass substrate coated with a transparent conductive film such as indium tin oxide (ITO) or fluorine-doped tin oxide (FTO) in a lithium tungsten oxide coating solution. That is, the glass substrate coated with the transparent conductive film is dipped in a bath filled with a lithium tungsten oxide coating solution. The glass substrate is immersed in the lithium tungsten oxide coating solution, and then the glass substrate is taken out while adjusting the extraction speed to 50 to 200 mm / min. Wipe the coating solution on the back side of the surface to be coated with ethanol. Of course, a polymer film such as polyethylene terephthalate (PET) may be used instead of the glass substrate.

The glass substrate coated with the lithium tungsten oxide coating solution is dried on a heating plate or drying oven at a predetermined temperature (for example, 80 to 120 ° C., preferably 100 ° C.) for a predetermined time (for example, 5 to 30 minutes), and then 500 ° C. or less. Heat treatment at a temperature of 100 to 500 ° C. to form a desired lithium tungsten oxide thin film. The drying causes the organic solvent such as alcohol contained in the lithium tungsten oxide coating solution to volatilize. If the heat treatment temperature is too low, the bonding force between the substrate and the lithium tungsten oxide thin film is weak, and can be easily peeled off. If the heat treatment temperature is too high, the electrochromic properties may be degraded because the film is densified. An amorphous lithium tungsten oxide thin film may be formed at a heat treatment temperature of less than 300 ° C., and a crystalline lithium tungsten oxide thin film may be formed at a heat treatment temperature in a range of 300 ° C. to 500 ° C. FIG.

The thickness of the coated lithium tungsten oxide thin film varies with the speed of drawing the glass substrate from the lithium tungsten oxide coating solution. When the drawing speed is increased, the thickness of the lithium tungsten oxide thin film becomes thick and the drawing speed is slowed. Since the thickness of the lithium tungsten oxide thin film is thinned, it is possible to control the thickness of the lithium tungsten oxide thin film by appropriately adjusting the extraction speed. In addition, the thickness of the coated lithium tungsten oxide thin film changes depending on the viscosity of the lithium tungsten oxide coating solution. Since the thickness of the oxide thin film becomes thick, the thickness of the lithium tungsten oxide thin film may be controlled by appropriately adjusting the viscosity of the lithium tungsten oxide coating solution.

The lithium tungsten oxide thin film thus prepared may be used as an electrochromic electrode, and a thin film such as CeO ₂ TiO ₂ , NiOOH, or prussian blue may be used as a counter electrode, and may be disposed between the electrochromic electrode and the counter electrode. An electrochromic device may be manufactured by filling and sealing an electrolyte such as lithium oxychloride (LiClO ₄ ).

The invention is described in more detail with reference to the following examples, which are not intended to limit the invention.

<Example 1>

Tungstic acid (H ₂ WO ₄ ) powder is dissolved in 30% hydrogen peroxide solution to a concentration of 1 M. Excess hydrogen peroxide and water are evaporated while the transparent tungsten solution in which tungstic acid (H ₂ WO ₄ ) is dissolved in hydrogen peroxide solution is heated to a temperature of 60 ° C. on a hot plate. The reaction stops when 20% by volume of the peroxotungstic acid compound remains. The resulting buffer rokso tungstate compound is a _{WO 3 · 0.13H 2 O 2 ·} 10.0H 2 O. The obtained peroxotungstic acid compound is added to ethanol to have a tungsten oxide concentration of 1 M to synthesize a transparent orange tungsten oxide solution. Dissolve LiClO ₄ to 1M in polycarbonate (PC) solution. The obtained 1M LiClO ₄ polycarbonate (PC) solution is mixed with the previously synthesized tungsten oxide solution to synthesize a Li _x WO ₃ coating solution so that the lithium (Li) content is 0.1 to 1 molar ratio relative to tungsten (W).

<Example 2>

Tungstic acid (H ₂ WO ₄ ) powder is dissolved in 30% hydrogen peroxide solution to a concentration of 1 M. Excess hydrogen peroxide and water are evaporated while bubbling N ₂ gas at a rate of 10 l / min while heating a transparent tungsten solution in which tungstic acid (H ₂ WO ₄ ) is dissolved in hydrogen peroxide solution at a temperature of 60 ° C. The reaction stops when 20% by volume of the peroxotungstic acid compound remains. The resulting buffer rokso tungstate compound is a _{WO 3 · 0.16H 2 O 2 ·} 7.10H 2 O. The obtained peroxotungstic acid compound is added to ethanol to have a tungsten oxide concentration of 1 M to synthesize a transparent orange tungsten oxide solution. Dissolve LiClO ₄ to 1M in polycarbonate (PC) solution. The obtained 1M LiClO ₄ polycarbonate (PC) solution is mixed with the previously synthesized tungsten oxide solution to synthesize a Li _x WO ₃ coating solution so that the lithium (Li) content is 0.1 to 1 molar ratio relative to tungsten (W).

<Example 3>

As in Example 1, tungstic acid (H ₂ WO ₄ ) powder is dissolved in 30% hydrogen peroxide solution to a concentration of 1 M. Excess hydrogen peroxide and water are evaporated while bubbling N ₂ gas at a rate of 10 l / min while heating a transparent tungsten solution in which tungstic acid (H ₂ WO ₄ ) is dissolved in hydrogen peroxide solution at a temperature of 60 ° C. After the reaction is carried out by N ₂ bubbling until about 20% by volume of the perfluoro tungstic acid compound remains, the reactant is placed in a rotary concentrator and the temperature is distilled under reduced pressure at about 60 ° C to obtain the peroxotungstic acid compound WO ₃ · 0.15. It is synthesized to have H ₂ O ₂ · 3H ₂ O form. The obtained compound is a compound which is dissolved in ethanol and water in solid form. The obtained peroxungstic acid compound is dissolved in ethanol to synthesize a solution such that the concentration of tungsten oxide is 1 M, and a tungsten oxide solution is synthesized. The tungsten oxide solution and the 1M LiClO ₄ polycarbonate (PC) solution obtained in Example 1 were mixed to synthesize a Li _x WO ₃ coating solution so that the lithium (Li) content was 0.1 to 1 molar ratio relative to tungsten (W).

<Example 4>

As in Example 1, tungstic acid (H ₂ WO ₄ ) powder is dissolved in 30% hydrogen peroxide solution. In Example 2, the excess solution of hydrogen peroxide and water was evaporated by bubbling N ₂ , but in this case, a transparent tungsten solution in which tungstic acid (H ₂ WO ₄ ) was dissolved in hydrogen peroxide solution was added to a rotary concentrator at 40 to 90 ° C. After distillation under reduced pressure, excess hydrogen peroxide and water are distilled off, and the reaction is allowed to remain until a solid peroxungate compound is left. The obtained compound is a _{WO 3 · 0.15H 2 O 2 ·} 0.5H 2 O. A tungsten oxide solution is synthesized by dissolving the obtained peroxotungic acid compound in ethanol so that the concentration of tungsten oxide is 1M. The tungsten oxide solution and the 1M LiClO ₄ polycarbonate (PC) solution obtained in Example 1 were mixed to synthesize a Li _x WO ₃ coating solution so that the lithium (Li) content was 0.1 to 1 molar ratio relative to tungsten (W).

Example 5

The lithium tungsten oxide coating solution synthesized in Examples 1 to 4 is coated on a glass substrate on which an indium tin oxide (ITO) transparent conductive film is formed by a dip coating method. That is, the glass substrate is immersed in the lithium tungsten oxide solution, and then the coating rate is adjusted to about 100 mm / min so that the thickness is about 200 nm. After coating the lithium tungsten oxide coating solution on the glass substrate, it is dried for 10 minutes at 100 ℃, heat treatment at 100 ~ 500 ℃ 1 hour to form a WO ₃ thin film.

Comparative Example

Tungstic acid (H ₂ WO ₄ ) powder is dissolved in 30% hydrogen peroxide solution to a concentration of 1 M. The excess tungsten peroxide and water are evaporated while the transparent tungsten solution in which tungstic acid (H ₂ WO ₄ ) is dissolved in hydrogen peroxide solution is heated to a temperature of 60 ° C. on a hot plate. The reaction stops when 20% by volume of the peroxotungstic acid compound remains. It was confirmed that the peroxungstic acid compound obtained at this time was WO ₃ · 0.13H ₂ O ₂ · 10.0H ₂ O by iodine titration and DSC / TG thermal analysis. The obtained peroxotungstic acid compound is added to ethanol to have a tungsten oxide concentration of 1 M to synthesize a transparent orange tungsten oxide solution.

The synthesized tungsten oxide solution is coated on a glass substrate on which an indium tin oxide (ITO) transparent conductive film is formed by a dip coating method. That is, the glass substrate is immersed in the tungsten oxide solution, and then the coating rate is adjusted to about 100 mm / min so that the thickness is about 200 nm. The tungsten oxide solution was coated on a glass substrate, dried at 100 ° C. for 10 minutes, and heat treated at 100 to 500 ° C. for 1 hour to form a WO ₃ thin film.

1 is a graph showing the XRD (X-Ray Diffraction) pattern of the heat treatment temperature of the WO _3, Figure 2 is a graph showing the XRD pattern of the heat treatment temperature of the Li _0.3 WO _3, in Figure 3 Li _0.5 WO ₃ A graph showing the XRD pattern according to the heat treatment temperature. 1 to 3, (a) shows a case of heat treatment at 200 ° C., (b) shows a case of heat treatment at 300 ° C., (c) shows a case of heat treatment at 400 ° C., and (d) shows 500. The case of heat processing at ° C is shown. 1 shows a case in which a tungsten oxide solution is synthesized and coated by a dip coating method according to a comparative example, and FIGS. 2 and 3 show a case in which a lithium tungsten acid cargo coating solution is synthesized and coated by a dip coating method. It is about the case.

1 to 3, it can be seen that the amorphous phase exists through the absence of the crystalline phase up to 300 ° C., respectively, and the crystalline phase began to appear at 400 ° C. FIG. For WO ₃ it is known that monoclinic crystals are produced at 400 ° C. and tetragonal crystals are produced at 500 ° C. In the case of Li _0.3 WO ₃ , it can be confirmed through the peak around 12-14 ^o that a crystal phase of Li ₂ W ₄ O ₁₃ is formed from 400 ° C. That is, it can be seen that the crystal phase of Li ₂ W ₄ O ₁₃ is generated while the WO ₃ crystal phase is present. The case of Li _0.5 WO ₃ is similar, but it can be seen that the peak around 23 ^o , the main peak of WO ₃ , decreases from three peaks to one. This is thought to be the conversion of the crystal peaks of WO ₃ into cubic with increasing lithium content.

4 are scanning electron micrographs of a Li _x WO ₃ thin film heat treated at 200 ° C. for 1 hour. 4 shows a case of forming a Li _x WO ₃ thin film by synthesizing a lithium tungsten oxide coating solution according to Example 2 and coated by a dip coating method, Figure 4 (a) is Li _0.1 WO ₃ x x 0.1 For thin films, (b) for Li _0.3 WO ₃ thin films with x of 0.3, (c) for Li _0.4 WO ₃ thin films with x of 0.4, and (d) for Li _0.5 WO with x of 0.5 _{3 for} thin film. Referring to FIG. 4, it can be seen that when the heat treatment is performed at 200 ° C. as shown in the XRD patterns shown in FIGS. 1 to 3, it is amorphous. On a scanning electron microscope, however, fine grains appear in the Li _0.1 WO ₃ thin film with x of _0.1 and the Li _0.3 WO ₃ thin film with x of 0.3, and the Li _0.4 WO ₃ thin film with x of _0.4 and x of 0.5 Although large grains appear to be present in the Li _0.5 WO ₃ thin film, it can be seen that they are all amorphous.

5 shows a scanning electron micrograph of a Li _0.3 WO ₃ thin film according to the heat treatment temperature. FIG. 5 illustrates a case of forming a Li _x WO ₃ thin film by synthesizing a lithium tungsten oxide coating solution according to Example 2 and coating the same by a dip coating method. FIG. (b) shows the case of heat treatment at 300 ° C, (c) shows the case of heat treatment at 400 ° C, and (d) shows the case of heat treatment at 500 ° C.

Referring to FIG. 5, it can be seen that the crystal phase does not appear up to 300 ° C., but at 400 ° C., plate crystals and rod crystals are formed. At 500 ° C., these crystals tend to be densified.

6 shows charge density characteristics of a lithium tungsten oxide (Li _x WO ₃ ) thin film according to the amount of lithium added. In FIG. 6, (a) shows the charge density of the WO ₃ thin film with x being 0, (b) shows the charge density of the Li _0.1 WO ₃ thin film with x being 0.1, and (c) is Li with x being 0.2 The charge density of a _0.2 WO ₃ thin film is shown, (d) shows the charge density of a Li _0.3 WO ₃ thin film with x of 0.3, and (e) the charge density of a Li _0.4 WO ₃ thin film with x of 0.4. (F) shows the charge density of a Li _0.5 WO ₃ thin film having x of 0.5. 6 (b) to (f) is a lithium tungsten oxide coating solution according to Example 2 synthesized and coated by a dip coating method A graph showing a case of forming a lithium tungsten oxide thin film by heat treatment at 200 ° C. for 1 hour, and synthesizing the tungsten oxide solution according to the comparative example of FIG. It is a graph when a tungsten oxide thin film is formed by heat treatment.

As shown in FIG. 6, the tungsten oxide film WO ₃ having no lithium added showed the largest charge density. The charge density was about 21 mC / cm ² until the molar ratio of tungsten to lithium was 0.3, and the lowest charge was when the molar ratio of lithium to tungsten was 0.4 ((e) in FIG. 6). Had a density.

7 is a graph showing a change in transmittance of a lithium tungsten oxide (Li _x WO ₃ ) thin film according to the addition of lithium ions. FIG. 7 is a view showing a lithium tungsten oxide (Li _x WO ₃ ) thin film and a tungsten oxide thin film manufactured under the same conditions as in FIG. 6, using a laser of 632 nm while applying a voltage of ± 1 V for 30 seconds. This is a value obtained by measuring the transmittance of the visible light region. In FIG. 7, (a) shows the transmittance of the WO ₃ thin film having x of 0, (b) shows the transmittance of the Li _0.1 WO ₃ thin film having x of 0.1, and (c) shows Li _0.2 WO having x of 0.2. ₃ shows the transmittance of the thin film, (d) shows the transmittance of the Li _0.3 WO ₃ thin film x is 0.3, (e) shows the transmittance of the Li _0.4 WO ₃ thin film x is 0.4, (f) The transmittance of the Li _0.5 WO ₃ thin film having x of 0.5 is shown.

Referring to FIG. 7, in the case of the tungsten oxide (WO ₃ ) thin film without lithium, the transmittance was changed from 90% for decolorization to 7% for coloring. The transmissivity did not change significantly depending on the amount of lithium added at about 10%, and the color loss was as low as 80% when the molar ratio of lithium ions to tungsten was 0.1 and 0.5. When the molar ratio of lithium ion to tungsten was 0.3, the transmittance was 95%, which was the highest when decolorizing. As shown in FIG. 7, the lithium-tungsten oxide containing lithium is faster than the tungsten oxide containing no lithium, and the response speed at the time of coloring and decolorizing is faster.

8 is a graph illustrating a cyclic voltammetry curve according to the lithium content. FIG. 8 is a graph showing changes in current when a voltage is applied at a scan rate of 50 mV / s in a ± 1V region for a lithium tungsten oxide (Li _x WO ₃ ) thin film and a tungsten oxide thin film manufactured under the same conditions as in FIG. 6. The characteristic is measured. In FIG. 8, (a) shows the current characteristics of the WO ₃ thin film where x is 0, (b) shows the current characteristics of the Li _0.1 WO ₃ thin film where x is 0.1, and (c) shows Li as x is 0.2. The current characteristics of the _0.2 WO ₃ thin film, (d) is the current characteristics of the Li _0.3 WO ₃ thin film x x 0.3, (e) is the current characteristics of the Li _0.4 WO ₃ thin film x x 0.4 , (f) shows the current characteristics of a Li _0.5 WO ₃ thin film having x of 0.5.

Referring to FIG. 8, in the case of tungsten oxide (WO ₃ ) film containing no lithium, the reduction current peak was 0.9 mA / cm 2, and the reduction current peak value was 0.2 mA at 0.6 mA / cm 2, and one oxide peak at 0.8 V. You can see that there is more. It can be seen that the redox current peak becomes small until the molar ratio of lithium ions to tungsten is 0.2. The molar ratio of lithium tungsten to tungsten was 0.3 when the molar ratio of lithium ion to tungsten was 0.4, and the redox current value decreased when the molar ratio of lithium ion to tungsten was 0.4, and the molar ratio of lithium ion to tungsten increased again from 0.5. .

9 is a graph showing the charge density characteristics of Li _0.3 WO ₃ thin film according to the heat treatment temperature. FIG. 9 is a view of a lithium tungsten oxide (Li _x WO ₃ ) thin film manufactured under the same conditions as in FIG. 6, in FIG. 9, (a) shows a heat treatment at 200 ° C., and (b) is at 300 ° C. FIG. The case of heat processing is shown, (c) shows the case of heat processing at 400 degreeC, and (d) shows the case of heat processing at 500 degreeC.

Referring to FIG. 9, it can be seen that when the heat treatment is performed at 200 ° C. and 300 ° C., they have almost similar charge densities, but have a charge density of 20 to 22 mC / cm ² . However, when the heat treatment at 400 ℃ or more it can be seen that the charge density is significantly reduced to about 6mC / cm ² . This is thought to be due to the drastic reduction of lithium ion in and out by crystallization.

FIG. 10 is a graph illustrating a change in transmittance of a Li _0.3 WO ₃ thin film according to annealing temperature, and is measured by using a laser of 632 nm while applying a voltage of ± 1 V for 30 seconds. . FIG. 10 is a view of a lithium tungsten oxide (Li _x WO ₃ ) thin film manufactured under the same conditions as in FIG. 6. In FIG. 10, (a) shows a heat treatment at 200 ° C., and (b) is at 300 ° C. FIG. The case of heat processing is shown, (c) shows the case of heat processing at 400 degreeC, and (d) shows the case of heat processing at 500 degreeC.

Referring to FIG. 10, in the case of the Li _0.3 WO ₃ thin film, the light transmittance of the Li _0.3 WO ₃ thin film was 200%, and the lowest value was 7%, and the transmittance was 92%. When the heat treatment temperature is 300 ° C, the transmittance was about 10% during coloring and the transmittance was 93% when discoloring. However, when the heat treatment temperature was increased to 400 ° C., the transmittance was 55% when pigmented, and the transmittance was 73% when decolorized. When heat-treated at 500 ° C., the transmittance was 58% and the transmittance was about 80%.

11 is a graph showing a cyclic voltammogram curve of a Li _0.3 WO ₃ thin film according to the heat treatment temperature. FIG. 11 is a view showing a lithium tungsten oxide (Li _x WO ₃ ) thin film manufactured under the same conditions as in FIG. 6, in FIG. 11, (a) shows a heat treatment at 200 ° C., and (b) is at 300 ° C. FIG. The case of heat processing is shown, (c) shows the case of heat processing at 400 degreeC, and (d) shows the case of heat processing at 500 degreeC. The current density of FIG. 11 was measured using cyclic voltametry (CV) using Ag / AgCl as a reference electrode and platinum (Pt) line as a counter electrode. to be.

11, when the heat treatment at 200 ℃ reduction current at -1.0V represents the peak value of 0.9mA / cm ^2, the peak value of the oxidation current represents 0.8mA / cm ² at 0V. When the heat treatment at 300 ℃ can be seen that the reduction current peak is reduced to 0.5mA / cm ² and the oxidation current is reduced to 0.4m / cm ² . It can be seen that the area of the cyclic voltammetry curve is greatly decreased when the heat treatment is performed at 400 ° C. or higher, indicating that the amount of ions entering and exiting the thin film is greatly reduced, and that the ion entrance and exit sites due to crystallization are greatly reduced. I think.

As mentioned above, although preferred embodiment of this invention was described in detail, this invention is not limited to the said embodiment, A various deformation | transformation by a person of ordinary skill in the art within the scope of the technical idea of this invention is carried out. This is possible.

1 is a graph showing an XRD pattern according to the heat treatment temperature of WO ₃ .

2 is a graph showing an XRD pattern according to the heat treatment temperature of Li _0.3 WO ₃ .

3 is a graph showing an XRD pattern according to the heat treatment temperature of Li _0.5 WO ₃ .

4 are scanning electron micrographs of a Li _x WO ₃ thin film heat treated at 200 ° C. for 1 hour.

5 is a scanning electron micrograph of a Li _0.3 WO ₃ thin film according to the heat treatment temperature.

6 is a graph showing charge density characteristics of a lithium tungsten oxide (Li _x WO ₃ ) thin film according to the amount of lithium added.

7 is a graph showing a change in transmittance of a lithium tungsten oxide (Li _x WO ₃ ) thin film according to the addition of lithium ions.

8 is a graph illustrating a cyclic voltammetry curve according to the lithium content.

9 is a graph showing the charge density characteristics of Li _0.3 WO ₃ thin film according to the heat treatment temperature.

10 is a graph showing a change in transmittance of a Li _0.3 WO ₃ thin film according to the heat treatment temperature.

11 is a graph showing a cyclic voltammogram curve of a Li _0.3 WO ₃ thin film according to the heat treatment temperature.

Claims (10)

(a) dissolving tungsten (W) metal powder or tungstic acid (H ₂ WO ₄ ) powder in hydrogen peroxide to form a transparent tungsten solution; (b) To remove a certain amount of water and hydrogen peroxide contained in the tungsten solution while heating at a temperature of 40 ~ 90 ℃ hydrogen peroxide and water to evaporate WO ₃ · xH ₂ O ₂ · yH ₂ O (0.05≤x≤1.0 Forming a transparent orange peroxungstic acid having a chemical formula of 0.5 ≦ y ≦ 10); (c) dissolving the peroxo tungstic acid in an organic solvent to form a tungsten oxide solution; (d) forming a lithium source solution in which mixing occurs well when mixed with the tungsten oxide solution, no separation of the solution, and no precipitation of lithium salt, lithium hydroxide and lithium tungsten occurs; And (e) mixing the lithium source solution and the tungsten oxide solution to form lithium tungsten oxide (Li _x WO ₃ ), The lithium tungsten oxide is a method of producing a lithium tungsten oxide coating material, characterized in that the molar ratio of lithium ions to tungsten ranges from 0.1 to 1. The method of claim 1, wherein the lithium source solution is a solution in which a lithium compound or a lithium salt is dissolved in an organic solvent, an alkoxide containing lithium, or a lithium amide-based solution. The method of claim 2, wherein the lithium compound or lithium salt is lithium fluoride (LiF), lithium chloride (LiCl), lithium hydroxide (LiOH), lithium carboxylate (LiCOOH), lithium nitrate (LiNO ₃ ), lithium sulfate (Li ₂ SO ₄ ), lithium oxychloride (LiClO ₄ ) and lithium pentamethylcyclopentadienyl at least one material selected from the above. The method of claim 2, wherein the organic solvent for dissolving the lithium compound or the lithium salt is at least one solvent selected from polycarbonate, tetrahydrofuran, alcohol, and water. According to claim 1, wherein step (b), In order to remove water and hydrogen peroxide, nitrogen (N ₂ ) gas is injected at 0.1 to 100 l / min while heating at a temperature of 40 to 90 ° C. while hydrogen peroxide and water are evaporated while bubbling the tungsten solution. Method for producing a lithium tungsten oxide coating material, characterized in that to form a. The method of claim 5, further comprising evaporating hydrogen peroxide and water while bubbling the tungsten solution, and then distilling under reduced pressure at a temperature of 40 to 90 ° C. using a rotary concentrator to form peroxungic acid. Method for producing a lithium tungsten oxide coating material, characterized in that the peroxotungic acid is a solid phase. According to claim 1, wherein step (b), A method for producing a lithium tungsten oxide coating material, characterized in that to form a solid peroxloxungic acid by distillation under reduced pressure using a rotary concentrator while heating at a temperature of 40 ~ 90 ℃ to remove water and hydrogen peroxide. The method of claim 1, wherein step (c) comprises: The tungsten tungstic acid is mixed with at least one organic solvent selected from methanol, ethanol, propanol, isopropyl alcohol and 2-methoxyethanol to have a concentration of 0.1 to 1 M to form a tungsten oxide solution. Method of producing an oxide coating material. A lithium conductive tungsten oxide coating solution according to any one of claims 8 to 8 is coated on a glass substrate coated with a transparent conductive film to a thickness of 50 nm to 1 μm using dip coating, spin coating, bar coating or slot die coating. And heat-treating at a temperature of 100 to 500 ° C. to form an amorphous lithium tungsten oxide thin film or a crystalline lithium tungsten oxide thin film. A lithium tungsten oxide thin film as an electrochromic electrode, and a CeO ₂ TiO ₂ , NiOOH or Flushian blue thin film as a counter electrode, wherein an electrolyte is filled and sealed between the electrochromic electrode and the counter electrode. To produce an electrochromic device.

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