KR20190139514A - Nickel oxide powder and method for preparing the same - Google Patents

Abstract

In an example of the present application, the present application relates to a nickel oxide powder, a nickel oxide thin film, and a method for manufacturing the same. The nickel oxide powder obtained through a specific intermediate according to a 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

The present application relates to nickel oxide powder and a method of manufacturing the same.

Nickel oxide (NiOx) powder is a material applied to various fields such as electrochromic film, gas sensor, battery cathode material, catalyst, hydrogen storage or semiconductor. 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 quantum size effects, surface effects. In particular, when the nickel oxide powder is spherical with a particle size of several tens of nanometers, the packing capacity of the powder may be improved and the efficiency per unit volume may be improved.

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

Another object of the present application is to provide a nickel oxide thin film comprising 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 one example of the present application, the present application relates to a method for producing nickel oxide powder. As will be explained below, the process of the present application is carried out through certain intermediates in the production of nickel oxide powder. Nickel oxide powders prepared via certain intermediates in accordance with the methods of the present application can provide improved performance in certain applications.

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

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

The kind of solvent used for the said composition is not specifically 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 heterologous salt component included in the composition may be a carbonate as described below.

In the stirring carried out for obtaining 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, stainless steel or glass reactors with impeller stirring systems can be used for stirring. In addition, the agitation may take 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, 120 minutes or more, 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. While stirring may be accompanied by a temperature increase, it is preferable to adjust the temperature so that stirring can be performed within the above temperature range.

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

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 be increased or aggregation between particles may occur. Increasing particle size or intergranular agglomeration results in a reduction in the specific surface area of the powder, which can lead to a decrease in the physical / chemical reactions associated with the use in which the powder is used.

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

According to an example of the present application, the heat treatment for the precipitate may be performed while flowing nitrogen or argon to the precipitate at a temperature of 300 ° C or more. That is, the heat treatment for the precipitate may be made under a nitrogen atmosphere or an argon atmosphere. The heat treatment of the precipitate under nitrogen or argon atmosphere can lead to an oxygen defect of nickel oxide, i.e. a decrease in the oxygen content of nickel oxide. The nickel oxide powder prepared according to the present application may be used in a conductive laminate in which a thin film including nickel oxide powder is formed on a conductive film. One of such laminates is an electrochromic film (eg, a laminate of an ITO and a nickel oxide thin film). For example, the reduction in the oxygen content of nickel oxide contributes to providing a sufficient migration path for the material (eg, electrolyte ions) involved in the electrochemical reaction in the nickel oxide thin film.

In one example, when the heat treatment is performed under a nitrogen or argon atmosphere, the oxygen content of the nickel oxide powder finally prepared may be 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, 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. In addition, the lower limit of the oxygen content of the nickel oxide powder may be 23.0 wt% or more. The oxygen content can 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 salt. In other words, the preparation method of the present application includes stirring a composition containing nickel salt and carbonate salt. 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 the improvement of the electrochemical properties of the nickel oxide thin film used for the conductive laminate.

Nickel salt in the present application 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. The kind of the nickel salt and the carbonate is not particularly limited.

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

In one example, sodium carbonate, sodium bicarbonate, potassium carbonate, barium carbonate, lithium carbonate, or the like may be used. In addition, one or more of these materials may be used.

In one example, the nickel salt-containing composition may optionally further comprise another metal or oxide or nitride of the other metal in addition to nickel. For example, a material such as aluminum nitrate may be added to the composition. When nickel oxide powder prepared using the above selective materials is applied to the conductive laminate, the 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 before the heat treatment after obtaining the precipitate. Through washing and drying, it is possible to increase the purity of the nickel oxide powder.

The means and washing conditions of the washing 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, the room temperature is a temperature in a state in which it is not artificially heated or reduced in temperature, and may mean, for example, a temperature between 15 and 30 ° C.

The means for drying and the 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 can be done using a device that induces an appropriate level of wind. In another example, the drying may be accomplished by leaving the precipitate for a suitable time in natural state or in vacuum without additional equipment. The drying may be at a lower temperature than the heat treatment described above. For example, it may be made at a temperature between 150 ° C and below and room temperature.

Nickel oxide powders produced via nickel carbonate intermediates according to the present application may have particle sizes of several hundred nanometers (nm) in size, for example, less than 100 nm, specifically tens of nanometers in size. In addition, the nickel oxide powder may have a generally spherical shape (or an ellipsoidal shape close to a spherical shape), as confirmed by the SEM image of the following Experimental Example. Nickel oxide powder that satisfies the size and shape (granular) in accordance with the present application when compared to powder particles having a size on the order of several hundred nanometers and / or having a non-spherical shape, such as a plate shape, is formed when forming a nickel oxide thin film. It is possible to improve the electrochemical reaction of the nickel oxide thin film by creating an environment favorable for packing the particles and suppressing the increase of voids in the nickel oxide thin film.

In yet another example of the present application, the present application relates to nickel oxide powder prepared according to the above-described preparation method. The powder may be used in various fields such as electrochromic film, gas sensor, battery cathode material, catalyst, hydrogen storage or semiconductor.

In general, as the particle size decreases, the nanoparticles increase the surface area per unit volume than the bulk material. When the surface area increases, the energy of the surface atoms becomes larger than that of the internal atoms. Nanomaterials have a high proportion of high energy surface atoms, so that the reaction occurs mainly on the surface of the material, resulting in excellent chemical reactivity. Therefore, when using a powder having a particle size of several tens of nanometers, it is possible to increase the reaction efficiency than using a powder having a larger particle size. In addition, when the size of the particles is spherical, the packing ratio is higher than that of particles having a one-dimensional or two-dimensional shape (for example, crystalline particles such as Comparative Examples 1 or 2). In thin films with high packing rates, the number of atoms participating in the reaction per unit volume increases, and the reaction efficiency may increase as the interparticle networking becomes smooth.

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 diameter 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 by a scanning electron microscope through an image analysis program Nikon NIS-Elements AR. Specifically, assuming a spherical (or near-spherical ellipsoidal) particle, the smallest particle, lower 25% particle, median (50%) particle, upper 25% particle, and largest particle, The average particle size can then be calculated.

Specifically, the nickel oxide powder may have a particle size 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 of the particle size has a generally spherical shape.

The nickel oxide having a particle size in the above range and generally having a 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 in the range of 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 known analyzers and methods. For example, the specific surface area may be a nitrogen adsorption / desorption Brunner-Emit-Teller specific surface area (SBET) of the particles using a BEL Japan Inc., BELSORPmax analyzer. If the specific surface area is less than the above range, it is difficult to form a dense thin film due to the large particle size. When the specific surface area exceeds the above range, the aggregation tendency between particles increases, so it is difficult to expect even dispersion in the coating liquid for forming the nickel oxide thin film, and as a result, the physical properties of the nickel oxide thin film may decrease.

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

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

The method for preparing a nickel oxide thin film may include: obtaining a precipitate by stirring a nickel salt-containing composition; obtaining the nickel oxide powder by heat treating the precipitate-containing composition at a temperature of 300 ° C. or higher; And preparing a coating solution including the nickel oxide powder, and drying the coating solution after applying the coating solution on a substrate. The same process as described above may be repeated until the process of preparing the coating liquid containing the nickel oxide powder, that is, the step of obtaining the nickel oxide powder.

Specifically, the method for producing a nickel oxide thin film of the present application, the nickel oxide powder obtained through the predetermined process described above is prepared in the form of a coating liquid by mixing with a predetermined solvent, and applying the coating liquid on a substrate and drying the It may further include.

The kind of the solvent mixed with the nickel oxide powder to form a coating liquid is not particularly limited. In one example, the solvent may be an alcohol. At this time, the type of alcohol for forming the coating liquid 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 liquid in order to improve the dispersibility of the coating liquid and to improve the adhesion of nickel oxide to the substrate. The grinding dispersion step may be performed before applying the coating liquid on the substrate.

The apparatus or method for performing the grinding dispersion step is not particularly limited. For example, the grinding dispersion step may be performed through a bead shaker, a paint shaker, a horizontal disk mill, or the like.

The method of apply | coating the said coating liquid on a base material is not specifically limited. Known wet coating methods, such as spin coating or bar coating, can be used.

The kind of base material to which the coating liquid is applied is not particularly limited. For example, it may be a conductive or nonconductive 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 laminated to a conductive substrate such as ITO after peeling off the release substrate.

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

The conductive substrate may include a metal and / or a 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 one or more selected from 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 single layer form continuously formed 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 galium oxide), FTO (Fluor doped Tin Oxide), AZO (Aluminum doped Zinc Oxide), GZO (Galium) doped Zinc Oxide (ATO), Antimony doped Tin Oxide (ATO), Indium doped Zinc Oxide (IZO), Niobium doped Titanium Oxide (NTO), zinc oxide (ZnO), or Cesium Tungsten Oxide (CTO) It doesn't happen.

In the present application, drying of the coating liquid applied on the substrate may be performed at 170 ° C. or less. Specifically, the coating liquid 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, a nickel oxide powder formed through heat treatment for a specific precursor is first obtained, and the obtained nickel oxide powder is applied onto 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 form a nickel oxide and a thin film including the same directly on the substrate by applying a precursor-containing coating solution capable of providing nickel oxide directly on the substrate and then performing heat treatment at a high temperature of about 200 ° C. or higher. It was. As such, when the nickel precursor-containing coating solution is heat-treated at a high temperature of 200 ° C. or more, the thin film and the substrate have rigid properties. Due to the difference in the manufacturing method as described above, a high temperature heat treatment for forming a coating liquid containing a nickel oxide precursor into a thin film is not necessary. Thus, when following the method of the present application, flexibility can be imparted to the thin film and the substrate laminated together.

In yet 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 prepared according to the manufacturing method described above, and the conductive substrate may include the material described above.

If the conductive substrate and the nickel oxide thin film can be included, the use of the conductive laminate is not particularly limited. For example, the conductive laminate may be used in various fields such as an electrochromic film, a gas sensor, a battery cathode material, a catalyst, hydrogen storage, or a semiconductor.

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

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

Experimental Example  1: Comparison of Properties of Intermediates and Nickel Oxide Powders

Example  One

After dropping an aqueous 0.25M sodium carbonate solution in a 0.25M nickel nitrate aqueous solution for 20 minutes, the mixture was stirred for 1 hour. At this time, water was used as the solvent. The precipitate (NiCO ₃ ) was washed with water and then vacuum dried. X-ray diffraction (XRD) analysis of washed and dried intermediates (NiCO ₃ ) was performed using Bruker D4 Endeavor. XRD analysis of the precipitate (NiCO ₃ ) is the same as a in FIG.

Then, the washed and dried NiCO ₃ precipitate was heat-treated in an air atmosphere and 350 ° C. for 2 hours to obtain nickel oxide powder. XRD analysis was performed on the obtained nickel oxide powder (FIG. 1D). Moreover, SEM image was taken about the obtained nickel oxide powder using 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 CTAB aqueous solution (0.37 g / 12.5 ml), and an aqueous nickel chloride solution (1.04 g / 32 ml) was added dropwise to obtain a precipitate (α-Ni (OH) ₂ ). Washed and dried as in Example 1. XRD analysis results of the precipitate (α-Ni (OH) ₂ ) is the same as b of FIG. 1.

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

Comparative example  2

Precipitate (β-Ni (OH)) ₂ while maintaining the solution of urea solution (5 g / 30 ml) mixed with a nickel nitrate solution (3 g / 10 ml) and heating at 90 ° C. for 3 hours. ) The precipitate was washed with water and then dried in vacuo. XRD analysis results of the precipitate (β-Ni (OH) ₂ ) is shown in c of FIG. 1.

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

Comparative example  3

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

It can be seen from FIG. 1 that the nickel carbonate intermediate of Example 1 (FIG. 1 a) has no crystallinity. On the other hand, it can be seen that α-Ni (OH) ₂ and β-Ni (OH) _{2, which} are intermediates of Comparative Examples 1 and 2 used in place of nickel carbonate, have crystallinity (b and c of FIG. 1).

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

On the other hand, when comparing the XRD results of Fig. 1d with the heat treatment of the intermediate of Fig. 1a and Fig. 1a, when the heat treatment is performed on the intermediate (nickel carbonate) of Example 1 that can be interpreted as amorphous It can be seen that the 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 be generated than in FIG. 1D.

Indeed, when comparing the SEM images (FIG. 2) for the nickel oxide thin films prepared from Example 1 and Comparative Examples 1 to 3, the flower-like in the Comparative Example 1 was different from the image of Example 1 in which the particles were amorphous. like) crystalline particles are observed, and in Comparative Example 2, crystalline particles in the form of a plate are observed, and in Comparative Example 3, it can be seen that the plate-shaped particles are mixed with particles of other shapes. And it is also confirmed through FIG. 2 that the particle size of Example 1 is smaller than those of the comparative particles.

Nickel oxide powder with less crystallinity can contribute to the formation of a more dense and uniform thin film, and thus can impart excellent electrochemical properties to nickel oxide powder with low crystallinity, and a film containing the same. In view of this, the nickel oxide powder of the example can provide a thinner and more uniform thin film than that of the comparative example.

Experimental Example  2: Specific surface area  compare

Nitrogen adsorption-desorption Brunner-Emit-Teller specific surface area (SBET) was measured using the BEL Japan Inc., BELSORPmax analyzer and the specific surface area which the particle | grains of Example 1, Comparative Example 1, and Comparative Example 3 have. 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 the nickel oxide powder of Example 1 has an appropriate level of specific surface area, thereby forming a dense thin film and at the same time preventing aggregation between particles.

Experimental Example  3: Comparison of Nickel Oxide Thin Film Characteristics (Conductive On laminate  For)

A half-cell comprising a stack of ITO / NiO and an electrolyte containing LiClO ₄ and propylene carbonate is prepared, and a potentiostat (PT) is used as a counter electrode (PARSTAT, Princeton Applied Research) The device was used to drive the half-cells (driving voltages of +0.5 V and −0.5 V applied alternately for 50 seconds each). While the device was being driven, the degree of transmission of light in the wavelength region of 350 nm to 1,200 nm was measured using a transmittance measuring device (Avantes, Netherlands), and the transmittance of visible light having a wavelength of 550 nm was recorded.

Example  2

Preparation of nickel oxide powder: A nickel oxide powder was prepared in the same manner as in Example 1, except that the following matters were applied differently. That is, after dropping a 0.25M sodium carbonate aqueous solution in a 0.25M nickel nitrate aqueous solution for 20 minutes and stirred for 1 hour. Water was used as the solvent. The precipitate (NiCO ₃ ) was washed with water and dried. The dried precipitate (powder) was heat-treated in nitrogen at 400 ° C. for 2 hours to obtain nickel oxide powder.

Preparation of a laminate of ITO / nickel oxide thin film : The obtained nickel oxide powder and the wet dispersant were added to ethanol at 10 to 20 wt% and dispersed through a beaker shaker for 3 days. The prepared dispersion sol was spin coated for several tens of seconds and coated on an ITO substrate, and dried at 130 ° C. for 30 minutes to obtain a laminate of ITO / nickel oxide thin films. The driving characteristics evaluation results for the laminate are shown in Table 2.

Example  3

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

Preparation of laminate of ITO / nickel oxide thin film : The laminate was prepared in the same manner as in Example 2. The driving characteristics evaluation results for the laminate are shown in Table 2.

Comparative example  4

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

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

Transmittance T1 (%) when coloring Transmittance T2 (%) when discoloring 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 * Coloring: Nickel oxide thin film is colored and transmittance is low
* Decolorization: Nickel oxide thin film is bleached to increase permeability

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

Claims (15)

Stirring the nickel salt containing composition to obtain a precipitate; And
Heat treating the precipitate-containing composition at a temperature of at least 300 ° C. to obtain nickel oxide powder;
Method for producing a nickel oxide powder comprising a. The method for producing nickel oxide powder according to claim 1, wherein the heat treatment for the precipitate is carried out in an air, vacuum, argon or nitrogen atmosphere. The method of claim 2, wherein the heat treatment of the precipitate is performed under nitrogen or argon atmosphere. The method for producing nickel oxide powder according to claim 1, wherein the nickel salt-containing composition is obtained by mixing nickel salt and carbonate salt. 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 bicarbonate, potassium carbonate, barium carbonate, or lithium carbonate. The method of claim 4, wherein the precipitate is nickel carbonate (NiCO ₃ ). 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 lower. The method for preparing nickel oxide powder according to claim 1, further comprising washing and drying the precipitate before the heat treatment after obtaining the precipitate. The method for producing nickel oxide powder according to claim 1, having a particle diameter of less than 100 nm. 12. The method of claim 11, wherein the nickel oxide powder has a particle diameter of less than 10 to 50 nm. The method for producing nickel oxide powder according to claim 1, wherein a full width at half maximum calculated in the 2θ angle range at which the peak appears during X-ray diffraction measurement satisfies the range of 1.5 to 5. Nickel oxide powder prepared according to the method of any one of claims 1 to 10, and has a particle diameter of less than 100 nm. Nickel oxide powder prepared according to the method of any one of claims 1 to 10, wherein the half width calculated in the 2θ angle range at which the peak appears during X-ray diffraction measurement satisfies the 1.5 to 5 range.

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