KR102507912B1 - Nickel oxide powder and method for preparing the same - Google Patents

Abstract

In an example relating to the present application, the present application relates to nickel oxide powder, nickel oxide thin films, and methods for producing them. Nickel oxide powder obtained through a specific intermediate according to the manufacturing method of the present application has a size of several tens of nanometers, has a spherical shape, and shows low crystallinity.

Description

Nickel oxide powder and method for preparing the same {Nickel oxide powder and method for preparing the same}

This application relates to nickel oxide powder and a manufacturing method thereof.

Nickel oxide (NiOx) powder is a material that is applied to various fields such as electrochromic films, gas sensors, battery cathode materials, catalysts, hydrogen storage or semiconductors. In the case of reducing the particle size of nickel oxide in the above applications, it is possible to improve the properties of the material compared to the bulk particles due to the quantum size effect and the surface effect. In particular, when the nickel oxide powder has a particle size of several tens of nanometers and has a spherical shape, the efficiency per unit volume can be improved while the degree of packing of the powder is excellent.

One object of the present application is to provide nickel oxide powder having a small particle size of several tens of nanometers (nm), spherical shape, and low crystallinity.

Another object of the present application is to provide a nickel oxide thin film containing the nickel oxide powder.

The above and other objects of the present application can all be solved by the present application described in detail below.

In an example relating to the present application, the present application relates to a method for producing nickel oxide powder. As explained below, the method of the present application is carried out through certain intermediates in the production of nickel oxide powder. Nickel oxide powders prepared via certain intermediates according to the methods of the present application may provide improved performance in certain applications.

In the present application, the method for producing the nickel oxide powder may include obtaining a precipitate by stirring a nickel salt-containing composition, and heat-treating the precipitate-containing composition at a temperature of 300 ° C. or higher to obtain a nickel oxide powder. .

The nickel salt-containing composition may further include, in addition to the nickel salt, a solvent component and a heterogeneous salt component for forming an intermediate that is a precipitate.

The type of solvent used in the composition is not particularly limited. For example, water may be used, or a mixed solvent in which water is mixed with an alcohol such as ethanol or methanol may be used. The heterogeneous salt component included in the composition may be a carbonate as described below.

In the stirring performed to obtain the precipitate, the method or apparatus for causing the stirring, and the stirring conditions (eg, stirring time, stirring temperature, etc.) are not particularly limited.

For example, a stainless steel or glass reactor with an impeller agitation system may be used for agitation. In addition, the stirring may take a time within the range of several minutes to several tens of hours or several minutes to several tens of hours. For example, the stirring time may be 5 minutes or more, 10 minutes or more, 30 minutes or more, 60 minutes or more, or 120 minutes or more, and may be 8 hours or less, 6 hours or less, 4 hours or less, or 2 hours or less. Although not particularly limited, the stirring may be performed at a temperature of 0 °C or higher, 10 °C or higher, or 20 °C or higher, and at a temperature of 60 °C or lower or 50 °C or lower. Although a temperature increase may be accompanied during stirring, it is preferable to control the temperature so that stirring can be performed within the above temperature range.

In the present application, the heat treatment temperature for the precipitate may be at least 300 °C. For example, it may be 305 °C or more, 310 °C or more, 315 °C or more, 320 °C or more, 325 °C or more, 330 °C or more, 335 °C or more, 340 °C or more, 345 °C or more, or 350 °C or more. When the heat treatment temperature is less than 300° C., unreacted substances or by-products such as nickel carbonate may remain in addition to the nickel oxide powder, and as a result, the desired powder cannot be sufficiently obtained in the present application.

In one example, the upper limit of the heat treatment temperature may be 700 ℃. Specifically, the heat treatment may be performed at 650 °C or less, 600 °C or less, 550 °C or less, 500 °C or less, or 450 °C or less. When the heat treatment temperature exceeds the above range, the particle size of the powder may increase or aggregation between particles may occur. When the particle size increases or inter-particle aggregation occurs, the specific surface area of the powder decreases, which may lead to a decrease in physical/chemical reactions related to the purpose for which the powder is used.

In one example, the heat treatment of the precipitate may be performed under air, vacuum, argon or nitrogen atmosphere. As a result of heat treatment in the atmosphere, the precipitate is converted to nickel oxide.

According to an example of the present application, the heat treatment of the precipitate may be performed while flowing nitrogen or argon to the precipitate at a temperature of 300 °C or higher. That is, heat treatment of the precipitate may be performed under a nitrogen atmosphere or an argon atmosphere. When the precipitate is heat-treated under a nitrogen or argon atmosphere, oxygen defects in nickel oxide, that is, a decrease in the oxygen content of nickel oxide may be induced. The nickel oxide powder manufactured according to the present application can be used in a conductive laminate in which a thin film containing nickel oxide powder is formed on a conductive film. One of such laminates is an electrochromic film (eg, a laminate of ITO and a nickel oxide thin film). Sieve), for example, the reduction in the oxygen content of nickel oxide contributes to providing a sufficient passage for substances (eg, electrolyte ions) involved in electrochemical reactions in the nickel oxide thin film.

In one example, when the heat treatment is performed under a nitrogen or argon atmosphere, the finally produced nickel oxide powder may have an oxygen content of 25 wt% or less. For example, the oxygen content of the nickel oxide powder is 24.9 wt% or less, 24.8 wt% or less, 24.7 wt% or less, 24.6 wt% or less, 24.5 wt% or less, 24.4 wt% or less, 24.3 wt% or less, 24.2 wt% or less or less, 24.1 wt% or less, 24.0 wt% or less, 23.9 wt% or less, 23.8 wt% or less, 23.7 wt% or less, 23.6 wt% or less, or 23.5 wt% or less. And, the lower limit of the oxygen content of the nickel oxide powder may be 23.0 wt% or more. The oxygen content may be analyzed using a known device, for example, an elemental analyzer (Flash 2000 series, Thermo Scientific).

In one example, the nickel salt-containing composition may include a nickel salt and a carbonate. In other words, the manufacturing method of the present application includes stirring a composition comprising a nickel salt and a carbonate. Accordingly, in the present application, nickel carbonate (NiCO ₃ ) is used as an intermediate for producing nickel oxide. As confirmed through the following examples, since the nickel carbonate obtained during the process of the manufacturing method of the present application is amorphous, it is possible to provide nickel oxide powder having low crystallinity even after heat treatment. Low crystallinity is believed to contribute to improving the electrochemical properties of the nickel oxide thin film used in the conductive laminate.

In the present application, a nickel salt may mean a material capable of providing nickel or nickel ions when mixed with a predetermined solvent. In addition, carbonate may refer to a material capable of providing carbonic acid or carbonate ions when mixed with a predetermined solvent. Types of the nickel salt and carbonate are not particularly limited.

In one example, nickel nitrate, nickel sulfide, nickel acetate, nickel chloride, nickel sulfate, nickel bromide, or nickel iodide may be used as the nickel salt. Also, one or more materials among these may be used.

In one example, sodium carbonate, sodium hydrogen carbonate, potassium carbonate, barium carbonate, or lithium carbonate may be used as the carbonate. Also, one or more materials among these may be used.

In one example, the nickel salt-containing composition may optionally further include a metal other than nickel or an oxide or nitride of the other metal. For example, a material such as aluminum nitrate may be added to the composition. When the nickel oxide powder prepared using the above selective materials is applied to the conductive laminate, conductivity can be improved.

In one example, the method for producing the nickel oxide powder may further include a washing step and/or a drying step for the precipitate after obtaining the precipitate and before heat treatment. Through washing and drying, the purity of the nickel oxide powder can be increased.

The washing means and washing conditions are not particularly limited, and washing may be appropriately performed according to known means and methods selected by those skilled in the art. For example, the washing may be performed using water or ionized water, and washing may be performed at room temperature. In the present application, room temperature is a temperature in a state where the temperature is not artificially warmed or reduced, and may mean, for example, a temperature between 15 and 30 °C.

The drying means and drying conditions are also not particularly limited, and drying may be appropriately performed according to known means and methods selected by those skilled in the art. For example, the drying may be performed using a device that generates an appropriate level of wind. In another example, the drying may be performed by leaving the precipitate in a natural state without an additional device or in a vacuum state for an appropriate time. The drying may be performed at a lower temperature than the heat treatment described above. For example, it can be made at a temperature between 150 °C or less and room temperature.

The nickel oxide powder produced through the nickel carbonate intermediate according to the present application may have a particle size of less than several hundred nanometers (nm), for example, less than 100 nm, specifically several tens of nanometers. In addition, the nickel oxide powder may have a substantially spherical shape (or an elliptical spherical shape close to the spherical shape), as confirmed through SEM images of the following experimental examples. Compared to powder particles having a size of several hundred nanometers and/or having a shape other than a spherical shape such as a plate shape, the nickel oxide powder satisfying the size and shape (granular shape) according to the present application is, when forming a nickel oxide thin film Since an environment favorable to packing of particles is created and the increase of voids in the nickel oxide thin film is suppressed, the electrochemical reaction of the nickel oxide thin film can be improved.

In another example of the present application, the present application relates to a nickel oxide powder produced according to the above-described manufacturing method. The powder can be used in various fields such as electrochromic films, gas sensors, battery cathode materials, catalysts, hydrogen storage, or semiconductors.

In general, as the particle size decreases, the surface area per unit volume of nanoparticles increases more than that of bulk materials. When the surface area increases, the energy of surface atoms becomes greater than the energy of internal atoms. Since nanomaterials have a high proportion of surface atoms having high energy, reactions mainly occur on the surface of the material, resulting in excellent chemical reactivity. Therefore, when powder having a particle size of several tens of nanometers is used, reaction efficiency can be increased compared to using powder having a particle size larger than that. In addition, when the size of the particles is spherical, the packing ratio is increased compared to the one-dimensional or two-dimensional particles (eg, crystalline particles such as Comparative Example 1 or 2). In a thin film with a high packing ratio, the number of atoms participating in the reaction per unit volume increases and the networking between particles becomes smooth, thereby increasing reaction efficiency.

In this regard, the nickel oxide powder obtained through the above process may have predetermined particle characteristics.

In one example, the nickel oxide powder may have a particle size of less than 100 nm. In the present application, the particle diameter refers to an average particle diameter obtained by correcting and analyzing a scale bar of an image taken with a scanning electron microscope through an image analysis program Nikon NIS-Elements AR. Specifically, assuming that the particles are spherical (or ellipsoidal, close to spherical), the smallest particle, the bottom 25% particle, the median (50%) particle, the top 25% particle, and the largest particle are displayed based on the measured value of the size. After that, the average particle size can be calculated.

Specifically, the nickel oxide powder may have a particle diameter of 90 nm or less, 80 nm or less, 70 nm or less, 60 nm or less, or 50 nm or less. The lower limit of the particle size of the nickel oxide powder may be 5 nm or more or 10 nm or more. The nickel oxide powder having the above particle size has a generally spherical shape.

The nickel oxide having a particle diameter within the above range and having a substantially spherical shape has a predetermined specific surface area. In one example, the nickel oxide powder of the present application may have a BET specific surface area ranging from 120 m ² /g to 400 m ² /g. More specifically, the nickel oxide powder has a specific surface area of 130 m ² /g, 140 m ² /g or 150 m ² /g or more, and 390 m ² /g or less, 380 m ² /g or less, 370 m ² /g It may have a specific surface area of 360 m ² /g or less and 350 m ² /g or less. The specific surface area may be measured using a known analyzer and method. For example, the specific surface area may be a nitrogen adsorption/desorption Bruner-Emmett-Teller specific surface area (SBET) of the particles measured using a BELSORPmax analyzer from BEL Japan Inc. When the specific surface area is less than the above range, it is difficult to form a dense thin film due to the large particle diameter. In addition, when the specific surface area exceeds the above range, since the aggregation tendency between particles increases, it is difficult to expect even dispersion in the coating solution for forming the nickel oxide thin film, and as a result, the physical properties of the nickel oxide thin film may be deteriorated.

The nickel oxide powder may have low crystallinity. In one example, the nickel oxide powder may be a powder having a full width at half maximum calculated in the 2θ angle range in which a peak of a predetermined size appears in the range of 1.5 to 5 during X-ray diffraction measurement. . Specifically, the powder may be a powder having a full width at half maximum for a peak observed in an angular region ranging from 40 ° to 45 ° in the range of 1.5 to 5 when X-ray diffraction is measured. XRD and full width at half maximum can be measured or calculated as described in the experimental examples below. When the full width at half maximum is less than 1.5, specifically less than 1.0, the peak is very steep, which means that the degree of crystallinity of the powder is high.

In another example related to the present application, the present application relates to a method for manufacturing a nickel oxide thin film.

The method for producing the nickel oxide thin film includes the steps of stirring a nickel salt-containing composition to obtain a precipitate, heat-treating the precipitate-containing composition at a temperature of 300 ° C. or higher to obtain a nickel oxide powder; and preparing a coating solution containing the nickel oxide powder, applying the coating solution on a substrate, and then drying the coating solution. The same process as described above may be repeated until the process up to preparing the coating liquid containing the nickel oxide powder, that is, the step of obtaining the nickel oxide powder.

Specifically, the method for manufacturing a nickel oxide thin film of the present application includes the steps of preparing a coating liquid by mixing the nickel oxide powder obtained through the predetermined process described above with a predetermined solvent, applying the coating liquid on a substrate, and then drying it. can include more.

The type of solvent that is mixed with the nickel oxide powder to form the coating solution is not particularly limited. In one example, the solvent may be alcohol. At this time, the type of alcohol for forming the coating solution is not particularly limited, and may be, for example, ethanol or methanol.

In one example, the manufacturing method of the present application may further include a grinding and dispersing step for the coating solution in order to improve the dispersibility of the coating solution and the adhesion of nickel oxide to the substrate. The grinding and dispersing step may be performed before applying the coating solution on the substrate.

A mechanism or method for performing the grinding and dispersing step is not particularly limited. For example, the grinding and dispersing step may be performed through a bead shaker, a paint shaker, or a horizontal disc mill.

A method of applying the coating solution on the substrate is not particularly limited. A known wet coating method, such as spin coating or bar coating, may be used.

The type of substrate to which the coating solution is applied is not particularly limited. For example, it may be a conductive or non-conductive substrate.

In one example, when the substrate is non-conductive, the substrate may be a release substrate. The nickel oxide thin film formed on the release substrate may be separated from the release substrate and then laminated to a conductive substrate such as ITO.

In another example, the substrate may be a so-called conductive substrate capable of performing an electrode function.

The conductive substrate may include metal and/or metal oxide. For example, the conductive substrate may be aluminum (Al), gold (Au), silver (Ag), platinum (Pt), palladium (Pd), titanium (Ti), nickel (Ni), tungsten (W), copper ( Cu), alloys thereof; And it may include one or more selected from the oxides of the metals listed above. Although not particularly limited, when the conductive substrate includes the metal-related components listed above, the conductive substrate may have a continuously formed single layer shape or may have a metal mesh shape. In addition, the conductive substrate may include a transparent conductive compound. Examples of the transparent conductive compound include ITO (Indium Tin Oxide), In ₂ O ₃ (indium oxide), IGO (indium gallium oxide), FTO (Fluor doped Tin Oxide), AZO (Aluminium doped Zinc Oxide), GZO (Galium doped zinc oxide), antimony doped tin oxide (ATO), indium doped zinc oxide (IZO), niobium doped titanium oxide (NTO), zink oxide (ZnO), or cesium tungsten oxide (CTO). it is not going to be

In the present application, drying of the coating solution applied on the substrate may be performed at 170 °C or less. Specifically, the coating solution may be dried at a temperature of 160 °C or less, 150 °C or less, 140 °C or less, or 130 °C or less. The alcohol solvent is removed through the drying, and the nickel oxide powder may be formed on the substrate in the form of a solid thin film. The lower limit of the drying temperature is not particularly limited, but may be, for example, 50 °C or higher, 60 °C or higher, or 70 °C or higher.

In the present application, nickel oxide powder formed through heat treatment for a specific precursor is first obtained, and the obtained nickel oxide powder is coated on a substrate and dried (at a relatively much lower temperature than heat treatment) to form a nickel oxide thin film. On the other hand, in the prior art, it is common to directly apply a coating solution containing a precursor capable of providing nickel oxide on a substrate and then heat-treat at a high temperature of about 200 ° C. or more to form nickel oxide and a thin film containing the same directly on the substrate. was As such, when the coating solution containing the nickel precursor is heat-treated at a high temperature of 200 ° C. or higher, the thin film and the substrate have rigid properties. Due to the difference in the manufacturing method as described above, in the present application, high-temperature heat treatment is not required to form a coating solution containing a nickel oxide precursor into a thin film. Therefore, in the case of following the method of the present application, flexibility can be imparted to the thin film and the substrate to be laminated together.

In another example of the present application, the present application relates to a conductive laminate. The conductive laminate may include a conductive substrate and a nickel oxide thin film.

The nickel oxide thin film may include nickel oxide powder manufactured according to the manufacturing method described above, and the conductive substrate may include the material described above.

As long as it can include a conductive substrate and a nickel oxide thin film, the use of the conductive laminate is not particularly limited. For example, the conductive laminate may be used in various fields such as electrochromic films, gas sensors, battery cathode materials, catalysts, hydrogen storage, or semiconductors.

According to an example of the present application, nickel oxide powder having a size of several tens of nanometers, spherical shape, and low crystallinity, and a nickel oxide thin film including the powder may be provided.

1 shows XRD analysis results for intermediates and/or nickel oxide powders used in Examples and Comparative Examples.
Figure 2 is a SEM image of the nickel oxide powder used in Examples and Comparative Examples.

Hereinafter, the present application will be described in detail through examples. However, the protection scope of the present application is not limited by the examples described below.

Example 1: Comparison of properties of intermediates and nickel oxide powders

Example One

A 0.25M sodium carbonate aqueous solution was dropped into a 0.25M nickel nitrate aqueous solution for 20 minutes, followed by stirring for 1 hour. At this time, water was used as a solvent. The precipitate (NiCO ₃ ) was washed with water and dried under vacuum. X-ray diffraction (XRD) analysis was performed on the washed and dried intermediate (NiCO ₃ ) using a Bruker D4 Endeavor. XRD analysis results for the precipitate (NiCO ₃ ) are shown in a of FIG.

Then, the washed and dried NiCO ₃ precipitate was heat-treated in an air atmosphere at 350° C. for 2 hours, and nickel oxide powder was obtained. XRD analysis was performed on the obtained nickel oxide powder (Fig. 1 d). Further, a SEM image was taken of the obtained nickel oxide powder using a HITACHI S-4800. The result is shown in FIG. 2(a).

comparative example One

2.25 ml of 25% NH ₄ OH was mixed with an aqueous CTAB solution (0.37 g/12.5 ml), and an aqueous solution of nickel chloride (1.04 g/32 ml) was added dropwise to the solution to obtain a precipitate (α-Ni(OH) ₂ ). Washed and dried as in Example 1. XRD analysis results for the precipitate (α-Ni(OH) ₂ ) are shown in b of FIG.

The dried powder was heat-treated for 2 hours in an air atmosphere and 400° C. in an electric furnace to obtain nickel oxide powder. The SEM image of the obtained nickel oxide powder is shown in FIG. 2(b).

comparative example 2

While mixing/stirring a solution of a mixture of an aqueous solution of urea (5g/30ml) with an aqueous solution of nickel nitrate (3g/10ml), heated to 90° C. and maintained for 3 hours, the precipitate (β-Ni(OH) ₂ ) was obtained. The precipitate was washed with water and dried under vacuum. XRD analysis results for the precipitate (β-Ni(OH) ₂ ) are shown in c of FIG.

The dried powder was heat-treated for 2 hours in an air atmosphere and 400° C. in an electric furnace to obtain nickel oxide powder. The SEM image of the obtained nickel oxide powder is shown in FIG. 2(c).

comparative example 3

A commercially available product from Aldrich (cat.no: 637130) was used as nickel oxide powder. The XRD pattern of the nickel oxide powder is shown in Fig. 1d, and the SEM image is shown in Fig. 2(d).

1, it can be seen that the nickel carbonate intermediate of Example 1 (a in FIG. 1) does not have crystallinity. On the other hand, it can be seen that α-Ni(OH) ₂ and β-Ni(OH) ₂ , intermediates of Comparative Examples 1 and 2 used instead of nickel carbonate, have crystallinity (b and c in FIG. 1 ).

In addition, comparing the crystallinity of the final nickel oxide powder through FIGS. 1 d and e, it can be confirmed that the crystallinity of the nickel oxide obtained in Example 1 obtained by heat-treating nickel carbonate is small (d in FIG. 1). On the other hand, it can be seen that the commercialized product of nickel oxide (e in FIG. 1) has high crystallinity. Specifically, in the case of nickel oxide obtained according to Practice 1 of the present application, the maximum peak of 2θ is observed in the range of 40 ° to 45 °, that is, about 43.2 °, at which time the full width at half maximum (FWHM) ( Calculated through Bruker's Diffrac EVA program) was calculated to be about 2.2. That is, the peak of the embodiment is gentle. On the other hand, looking at the XRD graph (e in FIG. 1) of Comparative Example 3, which is a commercialized product, it is clearly confirmed with the naked eye that the slope of the maximum peak is steep, and therefore the full width at half maximum will be very small. For reference, in e of FIG. 1, the full width at half maximum for the peak at about 43.2° was less than 1.

On the other hand, when comparing the XRD results of FIG. 1d in which the intermediates of FIG. 1a and FIG. 1a were heat-treated, the heat treatment of the intermediate (nickel carbonate) of Example 1, which can be interpreted as atypical, was slightly It can be seen that crystallinity is expressed. In other words, when the intermediates of Comparative Examples 1 and 2, which have higher crystallinity than nickel carbonate, which is the intermediate of Example 1, are heat treated, it can be predicted that greater crystallinity will occur than in FIG. 1d.

In fact, comparing the SEM images (FIG. 2) of the nickel oxide thin films prepared from Example 1 and Comparative Examples 1 to 3, unlike the image of Example 1 in which the particles are irregular, in Comparative Example 1, the flower-like (flower-like) like) shape crystalline particles were observed, in Comparative Example 2, plate-shaped crystalline particles were observed, and in Comparative Example 3, it can be seen that plate-shaped particles are mixed with other shaped particles. And, it is also confirmed through FIG. 2 that the particle size of Example 1 is smaller than those of the comparative example particles.

Nickel oxide powder with smaller crystallinity can contribute to the formation of a denser and more uniform thin film, and thus, excellent electrochemical properties can be imparted to the nickel oxide powder with lower crystallinity and a film including the same. Considering these points, the nickel oxide powder of Example can provide a more dense and more uniform thin film than that of Comparative Example.

Example 2: specific surface area comparison

The specific surface areas of the particles of Example 1, Comparative Example 1, and Comparative Example 3 were measured for nitrogen adsorption/desorption Bruner-Emmett-Teller specific surface area (SBET) using a BELSORPmax analyzer from BEL Japan Inc. The results are shown in Table 1.

Specific surface area (cm ² /g) Example 1 191.74 Comparative Example 1 92.98 Comparative Example 3 101.6

As shown in Table 1, it can be seen that since the nickel oxide powder of Example 1 has an appropriate level of specific surface area, it is possible to prevent aggregation between particles while forming a dense thin film.

Example 3: Comparison of nickel oxide thin film properties (conductivity to the laminate applied for)

Prepare a half-cell containing an electrolyte containing a laminate of ITO / NiO and LiClO ₄ and propylene carbonate as follows, and a potentiostat using pt as a counter electrode (PARSTAT, Princeton Applied Research) The half-cell was driven using the equipment (driving voltages of + 0.5 V and - 0.5 V were alternately applied for 50 seconds, respectively). During device operation, the transmittance of light in a wavelength range of 350 nm to 1,200 nm was measured by using a transmittance measuring instrument (Avantes, Netherlands), and transmittance for visible light having a wavelength of 550 nm was recorded.

Example 2

Preparation of nickel oxide powder: Nickel oxide powder was prepared in the same manner as in Example 1, but only the following items were applied differently. That is, 0.25 M sodium carbonate aqueous solution was dropped into 0.25 M nickel nitrate aqueous solution for 20 minutes, followed by stirring for 1 hour. Water was used as a solvent. The precipitate (NiCO ₃ ) was washed with water and then dried. The dried precipitate (powder) was heat-treated in nitrogen at 400 DEG C for 2 hours to obtain nickel oxide powder.

Preparation of ITO/Nickel Oxide Thin Film Laminate : The obtained nickel oxide powder and wet dispersant were added to ethanol at 10 to 20 wt% and dispersed for 3 days using a bead shaker. The prepared dispersion sol was spin-coated for several tens of seconds, coated on an ITO substrate, and dried at 130 °C for 30 minutes to obtain an ITO/nickel oxide thin film laminate. Table 2 shows the driving characteristic evaluation results for the laminate.

Example 3

Preparation of nickel oxide powder: Nickel oxide powder was prepared in the same manner as in Example 1.

Preparation of ITO/Nickel Oxide Thin Film Laminate : A laminate was manufactured in the same manner as in Example 2 above. Table 2 shows the driving characteristic evaluation results for the laminate.

comparative example 4

Nickel oxide powder: As in Comparative Example 3, a commercially available product from Aldrich (cat.no: 637130) was used.

Preparation of ITO/Nickel Oxide Thin Film Laminate : It was prepared under the same method and conditions as in Example 2. Table 2 shows the driving characteristic evaluation results for the laminate.

Transmittance T1 (%) when colored Transmittance T2 (%) during bleaching Transmittance difference (T2-T1) (%) Example 2 31.9 82.9 51 Example 3 27 75.3 48.3 Comparative Example 4 43.6 59 15.4 * Coloration: a state in which the nickel oxide thin film is colored and the transmittance is lowered
* Decolorization: A state in which the nickel oxide thin film is bleached and the transmittance is increased

From Table 2, it can be seen that the transmittance difference between the comparative example and the example is greater. This means that the change in optical properties of the electrochromic device manufactured according to the example is more pronounced than that of the comparative device. Through these results, it can be inferred that the nickel oxide thin film prepared according to the embodiment contributes to improving the electrochemical properties of the conductive substrate.

Claims (15)

stirring the nickel salt-containing composition to obtain a precipitate; and
Heat-treating the precipitate-containing composition at a temperature of 300 ° C. or higher to obtain nickel oxide powder; includes,
Heat treatment of the precipitate is performed under a nitrogen or argon atmosphere,
Wherein the nickel oxide powder has a full width at half maximum calculated in the 2θ angle range in which a peak appears in the range of 1.5 to 5 during X-ray diffraction measurement. delete delete The method of claim 1, wherein the nickel salt-containing composition is obtained by mixing a nickel salt and a carbonate. The method for producing nickel oxide powder according to claim 4, wherein the nickel salt is nickel nitrate, nickel sulfide, nickel acetate, nickel chloride, nickel sulfate, nickel bromide, or nickel iodide. The method for producing nickel oxide powder according to claim 4, wherein the carbonate is sodium carbonate, sodium hydrogen carbonate, potassium carbonate, barium carbonate, or lithium carbonate. The method of claim 4, wherein the precipitate is nickel carbonate (NiCO ₃ ). 8. The method of claim 7, wherein the nickel carbonate is amorphous. The method for producing nickel oxide powder according to claim 1, wherein the precipitate-containing composition is heat-treated at a temperature of 700 °C or less. The method for producing nickel oxide powder according to claim 1, wherein after obtaining the precipitate and before heat treatment, the precipitate is further washed and dried. The method according to claim 1, wherein the nickel oxide powder having a particle diameter of less than 100 nm is produced. The method according to claim 11, wherein the nickel oxide powder having a particle size of 10 to less than 50 nm is produced. delete A nickel oxide powder prepared according to the method of any one of claims 1 and 4 to 10, and having a particle diameter of less than 100 nm. A nickel oxide powder prepared according to the method of any one of claims 1 and 4 to 10.

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