Multi-element composite oxide powder, electrochemical device and catalyst using the same, and method for producing multi-element composite oxide powder

Abstract

The purpose of the present invention is to provide: a multicomponent system complex oxide powder that has high thermal stability, high capacity, high reversible reaction speed of the electrochromic property thereof, and a high catalyst activity; an electrochemical device and a catalyst using the powder; and a method for producing the multicomponent system complex oxide powder.　The present invention provides a multicomponent system complex oxide powder that includes oxide particles containing a complex oxide that includes oxygen and compositional metal elements including, at a content proportion of a total of 80 atm% or more, two or more types of hexavalent metal elements and two or more types of pentavalent metal elements. The oxide particles each have a major axis and a minor axis that intersects with the major axis, and each have a polygonal tunnel structure including at least one tunnel that has a shape of a polygon having five or more sides and that is along the major axis.

Description

[Technical field]

[0001] An embodiment of the present invention relates to a multi-element composite oxide powder, an electrochemical device and a catalyst using the same, and a method for producing the multi-element composite oxide powder. [Background technology]

[0002] Metal oxides and metal composite oxides are known to be used as electrochemical functional materials and catalysts in electrochemical devices, such as power storage devices and electrochromic elements.

[0003] Electricity storage devices are devices that can be charged and discharged, and their development is progressing as part of the efficient use of electricity. Various types of electricity storage devices have been developed, such as secondary batteries, capacitors, and electric double layer capacitors.

[0004] Electrochromic elements utilize the reversible change in optical properties that occurs when an electric charge is applied to a substance. Electrochromic elements are used in displays and dimming systems, taking advantage of their ability to change optical properties. Examples of dimming systems include dimming glass, dimming spectacles, and anti-glare mirrors. Dimming systems are also used in a variety of fields, including vehicles, aircraft, and buildings.

[0005] Examples of electrochemical functional materials used in materials for power storage devices and electrochromic elements include tungsten oxide powder and molybdenum oxide powder. As a means for improving the storage capacity and charge / discharge efficiency of materials applied to power storage devices, attempts have been made to impart hopping conduction characteristics to the materials. In addition, as a means for improving the speed of reversible reactions when a charge is applied to a material exhibiting electrochromic properties, attempts have been made to impart hopping conduction characteristics to the materials. Hopping conduction characteristics can be imparted, for example, by providing defects in oxides due to oxygen deficiencies or impurity doping.

[0006] Metal oxides and metal composite oxides are used as catalysts in a wide variety of applications. For example, in a method for producing unsaturated carboxylic acids such as acrylic acid and methacrylic acid, which are industrially used as raw materials for various synthetic resins, paints, and plasticizers, alkanes such as propane and isobutane are reacted with molybdenum (Mo), vanadium (V), tellurium (Te), and other metals (e.g., A method is known in which a gas-phase catalytic oxidation reaction is carried out in the presence of a catalyst containing a metal composite oxide containing niobium (Nb, etc.). In addition, a method is known in which a metal containing Mo, V, and antimony (Sb) as essential components is used. It is known that by using a catalyst containing a composite oxide, ethylene, which is industrially used as a basic raw material for various petrochemical products and polymer products, can be selectively produced from ethane through an oxidative dehydrogenation reaction at relatively low temperatures. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 6-279351 [Patent Document 2] Japanese Patent Publication No. 9-194213 [Patent Document 3] Japanese Patent Application Publication No. 10-175885 [Patent Document 4] Japanese Patent Publication No. 2005-138008 [Patent Document 5] Japanese Patent Publication No. 2010-111575 [Patent Document 6] Japanese Patent Application Publication No. 2011-108554 [Patent Document 7] International Publication No. WO2011 / 108472 [Patent Document 8] International Publication No. WO2016 / 039157 [Patent Document 9] International Publication No. WO2018 / 199020 [Patent Document 10] International Publication No. WO2019 / 163931 [Patent Document 11] International Publication No. WO2019 / 208364 [Patent Document 12] International Publication No. WO2020 / 196720 Summary of the Invention [Problem to be solved by the invention]

[0008] An object of the embodiments is to provide a multi-element composite oxide powder that has high thermal stability, high capacity, a high reversible reaction rate of electrochromic properties, and can exhibit high catalytic activity, an electrochemical device and a catalyst using the same, and a method for producing the multi-element composite oxide powder. [Means for solving the problem]

[0009] According to an embodiment, 2 types The present invention provides a multi-element composite oxide powder comprising oxide particles including a composite oxide containing oxygen and constituent metal elements, the constituent metal elements including a hexavalent metal element and two or more pentavalent metal elements in a total content of 80 atm % or more. The composite oxide contains a hexavalent metal element in a total ratio of 40 atm% to 90 atm%. The hexavalent metal element is composed of W and Mo. The composite oxide contains a pentavalent metal element in a total ratio of 9 atm% to 40 atm%. The pentavalent metal element is composed of two or more elements selected from the group consisting of Ta, Nb, and V. The oxide particles have a major axis and a minor axis intersecting the major axis, and have a polygonal tunnel structure including one or more polygonal tunnels having 5 or more sides aligned along the major axis. [Brief description of the drawings]

[0010] [Figure 1] FIG. 2 is a schematic perspective view showing an example of a multi-element composite oxide powder according to an embodiment. [Diagram 2] FIG. 2 is an enlarged conceptual diagram showing part L shown in FIG. [Diagram 3] FIG. 2 is an enlarged conceptual diagram showing an example of a portion S shown in FIG. 1 . [Figure 4] 2 is an enlarged conceptual view showing another example of the portion S shown in FIG. 1. [Diagram 5] FIG. 1 is a conceptual diagram showing an example of the structure of an electrochemical device according to an embodiment. [Figure 6] FIG. 4 is a conceptual diagram showing another example of the structure of the electrochemical device according to the embodiment. Embodiment

[0011] WO, an oxide of W or Mo 3 Or MoO 3 It is known that the electrical conductivity and active sites can be changed by reducing WO by, for example, introducing oxygen vacancies, and changing the crystal structure to one with a tunnel structure or layer structure in the crystal. However, the oxide obtained by reduction, for example, WO 2.72 , W 5 O 14 , and Mo 5 O 14 The crystal structure is unstable, and it is difficult to create particles with a stable structure. It was difficult. 6+ W 6+ Or V 5+ It has also been considered to obtain a crystal structure with a tunnel structure or layered structure without reduction by compounding Mo. However, when one element is compounded with Mo, for example, W can only be dissolved up to 30 atm% and V can only be dissolved up to 10 atm%. This is because the crystal structure is not stable when attempting to form a solid solution with W or more than 30 atm% and V or more than 10 atm%.

[0012] [Multi-component composite oxide powder] The multi-element composite oxide powder according to the embodiment is an oxide particle containing constituent metal elements and oxygen. The constituent metal elements contain two or more hexavalent metal elements and two or more pentavalent metal elements in a total content of 80 atm% or more. The oxide particle has a major axis and a minor axis, and has a polygonal tunnel structure in the crystal structure. The major axis and the minor axis intersect. The polygonal tunnel structure includes one or more polygonal tunnels having pentagons or more. The polygonal tunnels are continuously aligned along the major axis direction along the major axis of the oxide particle.

[0013] The above multi-element composite oxide powder is W 6+ and Mo 6+ In addition to hexavalent metal elements such as This includes particles of composite oxides that are composites of two or more metals. "Composited" refers to a state in which the metals are mixed at the atomic level and incorporated into the crystals. Therefore, it is distinguished from mixed powders that are simply a mixture of hexavalent metal oxide and pentavalent metal oxide. It is also distinguished from metal oxides that exist as unavoidable impurities.

[0014] By combining two or more metals with different valences, a composite oxide having a tunnel structure with a stabilized crystal structure is provided. In other words, the composite oxide has two or more hexavalent metals and two or more pentavalent metals.

[0015] Since the oxide particles have polygonal tunnels along their major axis, they can exhibit good performance as electrochemical functional materials when applied to electrochemical devices. Specifically, in an electricity storage device, the tunnel structure allows for high capacity and high-speed charging and discharging. In an electrochromic element, the tunnel structure increases the ion diffusion rate, thereby improving the response speed of the electrochromic element. In addition, the crystal structure is stabilized, improving the catalytic ability. Furthermore, such multi-element composite oxide powder can reduce the volume resistivity and can also exhibit excellent conductivity. Furthermore, since the melting point of the composite oxide is high, it also has high thermal stability.

[0016] Hereinafter, the multi-element composite oxide powder according to the embodiment may be simply referred to as “composite oxide powder.” In other words, the term “composite oxide powder” refers to a multi-element composite oxide powder.

[0017] The multi-component composite oxide powder includes composite oxide particles containing two or more hexavalent metal elements, two or more pentavalent metal elements, and oxygen. The proportion of the two or more hexavalent metal elements and two or more pentavalent metal elements among the constituent metal elements contained in the composite oxide is 80 atm% or more. It is preferable that the constituent metal elements contain hexavalent metal elements and pentavalent metal elements in a total proportion of 90 atm% or more.

[0018] The valence of the metal element contained in the complex oxide as a constituent metal element refers to the valence when the complex oxide maintains charge neutrality. For example, a complex oxide in an oxidized state may maintain charge neutrality. In addition, a complex oxide used as an electrochemical functional material in an electricity storage device may maintain charge neutrality when the electricity storage device is in a discharged state.

[0019] The hexavalent metal element is, for example, two or more selected from the group consisting of W, Mo, Cr, Re, and Mn. It is preferable that the hexavalent metal element contains at least W and Mo. In a preferred embodiment, the constituent metal elements contain hexavalent metal elements at a ratio of 40 atm % to 90 atm % in total, and in a more preferred embodiment, the constituent metal elements contain hexavalent metal elements at a ratio of 60 atm % to 90 atm % in total.

[0020] The valence of the constituent metal elements can be measured by X-ray photoelectron spectroscopy (XPS) analysis. The valence can be calculated from the chemical shift of the peak specific to each element obtained by XPS analysis.

[0021] For example, Ti is Ti2p 3 / 2 The chemical shift of the 459 eV peak corresponds to Ti. 4+ To be I understand. Also, V is V2p 3 / 2 From the 518 eV peak of 5+ In addition, Ta is Ta4f 7 / 2 From the 26 eV peak of Ta 5+ In addition, W is W4f 7 / 2 From the 36 eV peak of W 6+ The measurement conditions for the XPS analysis are: excitation X-ray: Al Kα 1,2 line (1486.6 eV), X-ray diameter: 200 μm, photoelectron detection angle: 45°.

[0022] The hexavalent metal elements among the constituent metal elements may consist only of W and Mo. Hexavalent metal elements In a preferred embodiment, the Mo element content A is at least W and Mo. Mo W element content A W Ratio of A W / A Mo is 0.5≦A W / A Mo When the content ratio of W to Mo is within this range, the capacity and electrochromicity of the composite oxide powder are improved. The Mo content A Mo and W element content A W The unit is atm%.

[0023] The pentavalent metal element includes, for example, two or more selected from the group consisting of Ta, Nb, and V. In one preferred embodiment, the constituent metal elements contain pentavalent metal elements at a total content of 9 atm% or more and 40 atm% or less. In a more preferred embodiment, the constituent metal elements contain pentavalent metal elements at a total content of 10 atm% or more and 40 atm% or less. The inclusion of pentavalent metal elements contributes to the high discharge capacity of the composite oxide. In addition, the inclusion of pentavalent metal elements improves the oxidizing power of the composite oxide. Therefore, it is possible to exert a high catalytic effect on the redox reaction.

[0024] The constituent metal elements of the multi-component composite oxide may further contain one or more tetravalent metal elements at a ratio of 1 atm% or more. When a tetravalent metal element is contained, the content ratio is preferably 3 atm% or more. The tetravalent metal element includes an element of Group 4A in the periodic table, and is, for example, one or more selected from the group consisting of Ti, Zr, and Hf. When the constituent metal elements contain a tetravalent metal element, it is desirable to contain at least Ti among these tetravalent metal elements. Of Ti, Zr, and Hf, TiO, which is the raw material of Ti, is preferable. 2 The upper limit of the content of tetravalent metal elements is 20 atm%.

[0025] The complex oxide contains one or more polygonal tunnels in its crystal structure. The oxide particles of the complex oxide have a major axis and a minor axis intersecting the major axis, and the polygonal tunnels are aligned along the major axis. The one or more polygonal tunnels referred to here refer to polygons with 5 or more sides, for example, pentagons and hexagons. The complex oxide may also contain a tetragonal tunnel. By including a pentagonal or more polygonal tunnel, the extraction rate of charge carrier ions accompanying charging and discharging of a storage battery and the diffusion rate of ions accompanying a reversible reaction in an electrochromic element are improved. Therefore, a complex oxide powder containing oxide particles having such a polygonal tunnel structure can be suitably applied to an electrochemical device as an electrochemical functional material. Note that the polygonal tunnel may be a polygon with 7 or more sides, but it is preferable to have a pentagon or hexagon.

[0026] It is desirable that the oxide particle includes 20 to 70 polygonal tunnels of pentagonal or higher in an area of ​​5 nm x 5 nm in a region of the surface intersecting the long axis direction, excluding the peripheral portion up to 1 nm wide from the outer periphery of the surface. The surface may be, for example, one end face along the long axis of the oxide particle or a cross section of the oxide particle. In this way, in the main region of the oxide particle excluding the peripheral portion, it is desirable to include 20 to 70 polygonal tunnels of pentagonal or higher in an area of ​​5 nm x 5 nm. 2 When the oxide particle contains 20 to 70 atoms per unit area, it exhibits good electrical and ionic conductivity and maintains the stability of the crystal structure. An amorphous phase can be formed in the peripheral area, which corresponds to a surface layer of about 1 nm, of the oxide particle.

[0027] In the 5 nm x 5 nm area, about 10 to 50 square tunnels can be included. 2 If the number of atoms per unit area is 50 or less, the stability of the crystal structure can be maintained. In addition, the absence of tetragonal tunnels may reduce ion conductivity. Therefore, in order to achieve both conductivity and crystal structure stability, polygonal tunnels with pentagons or more must be present at least 25 nm.2 It is preferable that there are 20 to 70 tunnels per square, and it is preferable that there are 10 to 50 rectangular tunnels per square.

[0028] The complex oxide may include, for example, particles with a high aspect ratio having a shape such as a needle shape, and may also include a layered structure in its crystal structure. In the layered structure, a plurality of layers each containing a metal element are arranged at intervals of 0.3 nm to 0.5 nm in the long axis direction of the needle-shaped oxide particle (which may correspond to the c-axis direction of the crystal structure, for example). Each layer intersects with the long axis direction. In other words, a plurality of layers are stacked along the direction in which the polygonal tunnel extends, and such a layered structure forms a columnar crystal structure. Since the complex oxide has a layered structure in the columnar crystal structure grown in the long axis direction, it can exhibit properties as an electrochemical functional material. A complex oxide having a large number of layered structures in its crystal structure can incorporate a large number of carrier ions such as Li ions between the layers (so-called intercalation), and further allows reversible insertion and removal of carrier ions. For this reason, it can be used as a storage battery with a large discharge capacity or an electrochromic element with high stability.

[0029] In such a composite oxide powder, it is desirable that the composite oxide has few oxygen vacancies and other site vacancies. In theory, it is desirable that the composite oxide does not have any vacancies. By having few oxygen vacancies and other site vacancies, a stable crystal structure can be maintained. Oxygen vacancies indicate a state in which some of the oxygen atoms constituting the crystal lattice are not present in the crystal lattice constituting the composite oxide. A state in which an element other than oxygen constituting the crystal lattice, for example, a part of a constituent metal element, is not present at the site of that element in the crystal structure corresponds to a site vacancy for that element.

[0030] The oxide particles may have an aspect ratio of 2 to 50. The aspect ratio here refers to the ratio of the major axis to the minor axis of the oxide particle (aspect ratio = major axis / minor axis). The oxide particles having an aspect ratio in the above range may have, for example, a needle-like, columnar, or rod-like shape.

[0031] According to a preferred embodiment, the composite oxide is represented by the general formula W a Mo b A x Ti y O z In the general formula, A is 2 or more selected from the group consisting of V, Ta, and Nb. Each subscript in the formula satisfies 0.5≦a / b≦2.5, 0.4≦a+b≦0.9, 0.09≦x≦0.6, 0≦y≦0.3, 2≦z≦3, and a+b+x+y=1. More preferably, each subscript satisfies 0.5≦a / b≦2.5, 0.6≦a+b≦0.9, 0.1≦x≦0.4 , 0≦y≦0.2, 2≦z≦3, and a+b+x+y=1. More preferably, the subscript y is 0.1 or less. (y≦0.1), and the subscript y may be equal to or greater than 0.03 (0.03≦y).

[0032] According to a specific example of the above embodiment, the composite oxide is represented by the following general formula I: W a Mo b A c O z …I.

[0033] In the above general formula I, A is 2 or more selected from the group consisting of V, Ta, and Nb. Each subscript in the formula satisfies 0.5≦a / b≦2.5, 0.4≦a+b≦0.9, 0.1≦c≦0.6, 2≦z≦3, and a+b+c=1. More preferably, each subscript satisfies 0.5≦a / b≦2.5, 0.6≦a+b≦0.9, 0.1≦c≦0.4, 2≦z <= 3, and a+b+c=1.

[0034] According to another embodiment of the above aspect, the composite oxide is represented by the following general formula II: W a Mo b A e Ti f O z …II.

[0035] In the above general formula II, A is 2 or more selected from the group consisting of V, Ta, and Nb. Each subscript in the formula satisfies 0.5≦a / b≦2.5, 0.4≦a+b≦0.9, 0.09≦e≦0.4, 0.01≦f≦0.3, 2≦z≦3, and a+b+e+f=1. More preferably, the sum of the subscripts a and b satisfies 0.6≦a+b≦0.9. Even more preferably, the subscript f is 0.1 or less (f≦0.1). Also, the subscript f is 0.03 or less. f may be above (0.03≦f). The subscripts a, b, c, e, f, x, y, and z in each general formula represent atomic ratios. In addition, unavoidable impurities may be contained in an atomic ratio of less than 0.01.

[0036] The above embodiments of the composite oxides represented by these general formulas are those in which the hexavalent metal elements consist only of W and Mo. The content ratio of W and Mo is 0.5≦A W / A Mo An example of a desirable embodiment that satisfies ≦2.5 The specific example represented by general formula I is an example that does not contain a tetravalent metal element, and the specific example represented by general formula II is an example that contains only titanium (Ti) as a tetravalent metal element. In addition, it is preferable that the multi-element composite oxide powder satisfying either of the general formula I and the general formula II is mainly composed of tetragonal crystals. By being tetragonal, the crystallinity can be stabilized. Whether or not the powder is mainly composed of tetragonal crystals can be analyzed by X-ray diffraction (XRD).

[0037] <Manufacturing method> The multi-element composite oxide powder according to the embodiment can be produced as follows: The method for producing the multi-element composite oxide powder includes mixing oxides of the constituent metal elements to obtain a mixed powder, subjecting the mixed powder to a plasma treatment, extracting a stable phase after the plasma treatment, and heat-treating the stable phase in an oxygen-containing atmosphere to obtain a composite oxide.

[0038] As the raw material of the multi-element composite oxide powder, oxides of the constituent metal elements are used. As the raw material, four or more kinds of metal oxides are used. For example, when producing a composite oxide powder containing a composite oxide containing W, Mo, V, and Nb as the constituent metal elements, tungsten trioxide (WO 3 ), molybdenum trioxide (MoO 3 ), vanadium pentoxide (V 2 O 5 ), and diphenyl pentoxide Of (Nb 2 O 5 The prepared samples were mixed to obtain a mixed powder of the raw materials. do. In addition to these, oxide powders with different valences may be used as raw materials. 2 , MoO 2 , V.O., V. 2 O 3 , V.O. 2 , NbO, Nb 2 O 3 , NbO 2 etc. In addition, it is preferable to use oxides of the constituent metal elements as raw materials. For example, when manufacturing a W-Mo-V-Ta-O-based composite oxide powder, it is preferable to use tungsten oxide powder, molybdenum oxide powder, vanadium oxide powder, and tantalum oxide powder. By using oxides of the constituent metal elements, it becomes easier to control the composition. If a composite oxide is used as a raw material, it may cause variation in the composition.

[0039] Metal oxide nanoparticles are obtained by subjecting the mixed powder to plasma treatment. For example, inductively coupled plasma treatment is used as the plasma treatment. Inductively coupled plasma treatment is a method that uses a plasma flame. For example, the mixed powder is introduced into the plasma flame by a carrier gas and sublimated. The mixed powder is heated in the plasma flame, for example, to 10,000°C or higher, and the sublimation occurs. The sublimated gas is then rapidly cooled to room temperature in an oxygen atmosphere, causing sublimation, resulting in the production of a mixed oxide of the constituent metals. The particle size of the resulting powder particles can be controlled by controlling the speed at which the powder is fed into the plasma. For example, by feeding the sample at 100 g / min or less, The average particle size can be less than 1 μm, or even 100 nm or less.

[0040] In addition, in the method of adding four or more kinds of metal oxide powders to the plasma flame, there may be a discrepancy between the composition ratio of the added metal oxides and the composition ratio of the resulting composite oxide. This is because the melting points or boiling points of the raw metal oxides are different. Therefore, it is possible to control the composition by understanding the discrepancy in composition between the added metal oxides and the resulting composite oxide. When composition deviation occurs, multiple composite oxides with different composition ratios (complex oxides of four or more elements) may be formed. Even if multiple composite oxides of four or more elements with different composition ratios exist, the oxide powder can still be used. However, if the composition deviation is too large, the performance may decrease. In addition, in order to control the composition deviation, it is preferable to mix the four or more metal oxide powders as raw materials before feeding them into the plasma flame. A method for mixing the four or more metal oxide powders as raw materials includes using a mixer such as a ball mill. In addition, the mixing may be performed either by dry or wet method, but wet mixing is preferable. By forming a slurry by the wet method, it becomes easier to control the amount of the material fed into the plasma flame. In other words, a composite oxide having four or more constituent metal elements can be formed by feeding a raw material powder obtained by mixing four or more metal oxide powders into the plasma flame.

[0041] It is preferable that the plasma treatment is carried out in an oxygen-containing atmosphere. For example, in the plasma treatment, N 2 and O 2 or Ar and O 2A mixture of oxygen and fluorine is used as a carrier gas. By performing plasma treatment in an oxygen-containing atmosphere, the amount of oxygen vacancies that occur in the nanoparticles of the metal oxide can be controlled. Although the oxygen vacancies can be eliminated by performing a subsequent heat treatment, it is desirable to reduce the oxygen vacancies beforehand in order to prevent oxygen vacancies from remaining unintentionally.

[0042] The powder obtained after the plasma treatment may contain a mixture of nanoparticles having a primary particle size of less than 1 μm and coarse particles having a primary particle size of 1 μm or more. Of these powder particles, nanoparticles having a size of less than 1 μm are extracted as a stable phase and used as an intermediate product. For example, the stable phase can be separated by sieving and removing the coarse particles having a size of 1 μm or more. The reason for extracting the stable phase is that the coarse particles may not be stable in reaction with the composite oxide. In addition, if the reaction with the composite oxide is not stable, there is a possibility that a predetermined amount of tunnel structures having pentagons or more may not be formed. In addition, the particle size of the composite oxide particles is preferably less than 1 μm, and even more preferably 100 nm or less. This is because smaller particles are more stable in the composite reaction. The separation of coarse particles can be achieved by sieving using a sieve with suitable openings, or by cyclone separation. Cyclones are sometimes called powder separators. Cyclones are a type of centrifuge. Cyclone separation uses airflow to separate nanoparticles smaller than 1 μm.

[0043] The extracted stable phase is subjected to heat treatment in an oxygen-containing atmosphere. For example, the stable phase is sintered in air. The heat treatment advances crystallization, and a composite oxide without oxygen deficiency is obtained. The heat treatment is performed, for example, at a temperature in the range of 550°C to 1250°C. A heat treatment temperature of 550°C to 800°C is preferable. The heat treatment is performed, for example, for one hour or more. In addition, the composite oxide powder after the heat treatment is accompanied by grain growth. For this reason, the particle size of the composite oxide powder may be more than 1 μm. The upper limit of the particle size of the composite oxide powder is not particularly limited, but is preferably 10 μm or less. If the particle size is larger than 30 μm, the surface area cannot be gained, and the performance as an electrode layer or catalyst may be reduced. From this point of view, it is preferable that the average particle size of the composite oxide powder after the heat treatment is 30 μm or less, and further less than 1 μm.

[0044] <Measurement method> This paper describes the method of confirming the composition and crystal structure of the complex oxide, and the method of measuring the particle size of the oxide particles. Confirmation of the crystal structure includes confirmation of the polygonal tunnel structure. Measurement of the particle size includes measurement of the major axis, minor axis, and aspect ratio of the oxide particles.

[0045] (Method of measuring composition) The composition of the complex oxide contained in the multi-element complex oxide powder, i.e., the content of the constituent metal elements and oxygen, can be determined by measurement using inductively coupled plasma (ICP) optical emission spectroscopy and measurement using inert gas fusion-infrared absorption method, respectively.

[0046] First, the method for measuring the amount of metal elements using ICP atomic emission spectrometry will be explained. A sample is weighed out in a closed container, decomposed by heating with hydrofluoric acid and nitric acid, and then made to a constant volume with pure water. The amount of metal elements in the resulting solution is measured using ICP atomic emission spectrometry to determine the content of various metal elements in the sample.

[0047] The amount of oxygen can be determined as follows: A sample is weighed and the oxygen content in the sample is measured by inert gas fusion-infrared absorption method.

[0048] The amount of metal elements detected by ICP atomic emission spectrometry is taken as 100 atm%. The total of hexavalent and pentavalent metal elements is calculated from that amount. The proportion of tetravalent metal elements is also calculated by taking the amount of metal elements detected by ICP atomic emission spectrometry as 100 atm%.

[0049] (Confirmation of crystal structure) The polygonal tunnel structure contained in the crystal structure of the complex oxide was analyzed using a scanning transmission electron microscope (STEM) The HAADF-STEM image is used for STEM analysis (Scanning Transmission Electron Microscopy analysis). Angle Annular Dark Field-Scanning Transmission Electron Microscopy Hereafter, HAADF-STEM images are simply referred to as STEM images. In STEM images, metal elements can appear as white dots.

[0050] For STEM observation, the accelerating voltage of the STEM is set to 200 kV and the magnification is set to 10,000,000 times.

[0051] Whether or not the crystal structure contains polygonal tunnel structures can be confirmed by performing the following measurements. To perform STEM observation of the tunnel structures, prepare a fine sample of the complex oxide powder using the dispersion method or a microtome. If the particle diameter in the sample is less than 100 nm, prepare a sample with a thickness of 50 nm-100 nm using the dispersion method. If the particle diameter is 100 nm or more, prepare a sample with a thickness of 50 nm-100 nm using a microtome.

[0052] STEM observation is performed from the long axis direction along the long diameter of the oxide particle, and a STEM image is obtained that includes an area of ​​at least 5 nm x 5 nm, excluding the 1 nm wide portion (periphery) of the outer periphery of the oxide particle. The long axis direction of the oxide particle before sample preparation can be parallel to the c-axis direction of the structural crystal. In the STEM image, a portion with an area of ​​5 nm x 5 nm, excluding the peripheral portion, is observed. This area of ​​25 nm 2 In the area, among the white dots representing metal atoms, those whose centers are 0 nm or more and 0.5 nm or less apart are connected with lines to define polygons with 5 or more sides. The areas in the pentagons and hexagons defined by connecting the white dots where no white dots are visible are determined to be polygonal tunnels. Furthermore, when polygonal tunnels are observed as a result of such STEM observation from the long axis direction, it is deemed that there is a polygonal tunnel with 5 or more sides along the long axis along the particle long diameter. Furthermore, areas in which no white dots are visible within a square can also be determined to be tunnels, but the number of square tunnels is not included in the number of polygonal tunnels with 5 or more sides. Furthermore, even if no white dots are visible within a triangle, it is highly likely that the triangle is not a tunnel. Therefore, triangles are not considered to be tunnels.

[0053] A sample with a thickness of 50 nm or more has more than 100 layers, and if there are metal atoms in them, they are observed as white dots. Therefore, if there are no white dots, it can be determined that it is a tunnel. Also, if a tunnel structure is found when measured from the long axis direction, it can be said to have a columnar crystal structure grown in the long axis direction.

[0054] A specific example of the measurement will be described with reference to FIGS.

[0055] Fig. 1 is a schematic perspective view showing a multi-element composite oxide powder according to an embodiment. Fig. 2 is an enlarged conceptual diagram showing part L shown in Fig. 1. Figs. 3 and 4 are each an enlarged conceptual diagram showing an example of part S shown in Fig. 1.

[0056] The oxide particle 1 of the multi-element composite oxide powder shown in FIG. 1 has a major axis along a first direction 100 and a minor axis intersecting the first direction 100. In the illustrated example, the oxide particle 1 is shown as having a cylindrical shape, but the shape of the oxide particle 1 is not limited to that shown. The oxide particle 1 includes a side surface 2 in the major axis direction along the first direction 100 and a surface 3 intersecting the first direction 100. The surface 3 may be a cross section exposed during sample preparation using a microtome. Alternatively, the surface 3 includes a main region 3a and a peripheral portion 3b corresponding to a portion of the periphery of 1 nm.

[0057] Fig. 2 corresponds to a STEM image obtained by STEM measurement of a side surface 2 in the longitudinal direction of an oxide particle 1. By performing STEM observation of the side surface 2 from a direction intersecting with a first direction 100, a STEM image as shown in Fig. 2 can be obtained. In the example shown, layers 8 in which metal atoms 9 are aligned in a line are arranged approximately parallel to each other with a distance D of 0.3 nm to 0.5 nm between them, and it can be confirmed that there is a layered structure.

[0058] Figures 3 and 4 show the state in which metal atoms 9 are connected in STEM images obtained by STEM measurement of part S having an area of ​​5 nm x 5 nm in the main region 3a of the surface 3 excluding the peripheral portion 3b, for each of different examples of oxide particles. As described above, in an actual STEM image, metal atoms are observed as white dots, but for clarity of the drawings, the colors are inverted and the images are shown as black dots. Similarly, the white parts in Figures 3 and 4 appear black in the actual STEM images. Note that Figures 3 and 4 are schematic diagrams of 5 nm x 5 nm STEM images. Tunnel shapes that are cut off at the edge of the STEM image are not counted in the number of tunnel shapes. In other words, only tunnel shapes whose outlines can be observed in the 5 nm x 5 nm STEM image are counted.

[0059] The example shown in Figure 3 represents a STEM analysis illustrating the crystal structure of Example 1 described below. In this example, 39 pentagonal tunnels 5 and 8 hexagonal tunnels 6 can be identified. Also, 27 square tunnels can be identified.

[0060] The example shown in Figure 4 represents a STEM analysis illustrating the crystal structure of Example 5, which will be described later. In this example, 31 pentagonal tunnels 5 can be confirmed. In addition, 32 square tunnels can be confirmed.

[0061] (Method of measuring particle size) To measure the major axis, minor axis, and aspect ratio of the oxide particles, the composite oxide powder is observed using a transmission electron microscope (TEM). The TEM may be a STEM. For example, a TEM image magnified 30,000 times is used. The major axis and minor axis of the oxide particles shown in the TEM image are measured. The major axis is the longest diagonal line. The length extended vertically from the midpoint of the major axis is the minor axis. The major axis and minor axis are measured for 10 oxide particles. The average values ​​of the major axis and minor axis are the average particle size of the major axis and the average particle size of the minor axis. The aspect ratio is calculated by "average particle size of the major axis / average particle size of the minor axis".

[0062] [Electrochemical Devices] The multi-element complex oxide powder according to the embodiment can be applied and contained as an electrochemical functional material in an electrochemical device, for example. Examples of the application of the multi-element complex oxide powder as an electrochemical functional material include an electrode material for an electricity storage device and an electrode material for an electrochromic element. In addition, by imparting electrical conductivity to the multi-element complex oxide powder according to the embodiment, the volume resistance value of the film can be reduced.

[0063] An example of an electricity storage device is one in which a negative electrode and a positive electrode face each other via a non-conductive layer, and an electrolyte is used. This example of a device is capable of repeatedly storing (charging) and releasing (discharging) electric charges through oxidation-reduction reactions and ion adsorption and desorption. It does not generate electricity by itself, as does a solar cell. Specific examples of electricity storage devices include condensers and capacitors, as well as lithium-ion secondary batteries.

[0064] Electrode materials using such multi-element composite oxide powders can carry out both redox reactions and ion adsorption / desorption. Therefore, the electrode materials can be used in a variety of power storage devices. The presence or absence of redox reactions can be confirmed by cyclic voltammetry. When charging and discharging at a constant scanning voltage, a peak is observed at a specific voltage if a redox reaction occurs. No peak is observed for ion adsorption / desorption.

[0065] Fig. 5 shows a conceptual diagram illustrating the configuration of an electricity storage device. This diagram is a conceptual diagram illustrating an example of the structure of an electrochemical device according to an embodiment. The illustrated electricity storage device 10 includes a negative electrode layer 11, a negative electrode layer 12, a separator layer 13, a positive electrode layer 14, and a positive electrode layer 15. This diagram shows the structure of the cell portion.

[0066] In the electricity storage device 10, a negative electrode layer 12 and a positive electrode layer 14 are disposed on one main surface of a separator layer 13 and the other main surface on the rear side thereof, respectively. The side facing the separator layer 13 is regarded as the inside, and a negative electrode layer 11 is provided on the outside of the negative electrode layer 12. Similarly, a positive electrode layer 15 is provided on the outside of the positive electrode layer 14.

[0067] The negative electrode layer 11 and the positive electrode layer 15 are made of a material having electrical conductivity. Examples of the material having electrical conductivity include aluminum, copper, stainless steel, platinum, ITO, IZO, FTO, and SnO. 2 , InO 3 The thickness is preferably within the range of 5 μm to 50 μm.

[0068] Either the negative electrode layer 12 or the positive electrode layer 14 is an electrode layer containing the multi-component complex oxide powder according to the embodiment as an electrode material. An electrode layer using such a multi-component complex oxide powder is preferably used for the negative electrode layer 12. An electrode layer using such a multi-component complex oxide powder may be used for both the negative electrode layer 12 and the positive electrode layer 14.

[0069] In addition, when the electrode layer using such a multi-element composite oxide powder is used for the negative electrode layer 12, LiCoO 2 , LiMnO 2 , LiNiO 2 It is preferable to use Li composite oxides such as the above. The one with a lower potential based on the Li counter electrode becomes the negative electrode, and the one with a higher potential becomes the positive electrode. In combination with the above-mentioned positive electrode layer, the electrode layer using such multi-element composite oxide powder becomes the negative electrode layer. The above-mentioned Li composite oxide is a general-purpose positive electrode active material. In other words, by using the electrode layer according to the embodiment as the negative electrode layer, it is possible to impart performance as an electricity storage device.

[0070] In addition, it is preferable that the electrode layer contains the multi-element composite oxide powder according to the embodiment in a range of 50 mass % to 100 mass %. Other additives in the electrode layer include conductive powder and binder. The conductive powder includes carbon powder such as acetylene black.

[0071] The thickness of the electrode layer is not particularly limited, but is preferably 1 μm or more and 100 μm or less. If the thickness of the electrode layer is less than 1 μm, the absolute amount of the electrode material is small, so the capacity cannot be obtained. Also, if the thickness is more than 100 μm, the internal resistance of the electrode layer may increase. If the internal resistance increases, the charging and discharging speed decreases.

[0072] The porosity of the electrode layer is preferably 10% or more and 80% or less. By providing voids in the electrode layer, the area in contact with the electrolyte can be increased.

[0073] In addition, since the oxide particles of the multi-element composite oxide powder, which is the electrode material, have a polygonal tunnel structure, the contact area with the electrolyte can be secured even if the porosity of the electrode layer is somewhat low. The porosity of the electrode layer is more preferably 10% or more and 50% or less. The porosity of the electrode layer may be 20% or more and 80% or less.

[0074] The separator layer 13 is for providing a certain distance between the negative electrode layer 12 and the positive electrode layer 14. Examples of the separator layer 13 include porous layers such as a polyethylene porous layer and a polypropylene porous layer. The separator layer 13 can be impregnated with an electrolyte solution containing Li ions. The electrolyte solution can be an organic solvent or an ionic liquid. The organic solvent can be ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), gamma butyrolactone (γ-BL), valerolactone (VL), and the like. The electrolyte may be LiPF 6 , LiBF 4 , LiClO 4 , LiCF 3 SO 3 and mixed electrolytes thereof.

[0075] The power storage device may have a cell having the above-mentioned laminated structure. In order to increase capacity, the cell structure may be multi-layered or may be wound into a long length.

[0076] Such power storage devices can be used, for example, in vehicles, electronic devices, and mechanical equipment.

[0077] Examples of the vehicle include automobiles, electric railways, etc. Examples of the automobile include automobiles driven by a motor, such as hybrid automobiles and electric automobiles. The automobiles are not particularly limited, and may include private cars, buses, crane trucks, trucks, etc.

[0078] The electronic device refers to a device that is driven by electricity. The mechanical equipment refers to a device that is operated. Examples of the mechanical equipment include elevators, cranes, robots, medical equipment, and machine tools.

[0079] Electrochromic devices are materials that undergo a reversible change in optical properties when an electric charge is applied.

[0080] When the multi-element complex oxide powder according to the embodiment is used in the electrochromic layer of an electrochromic element, the porosity of the layer is preferably 30% or less, more preferably 10% or less. In order to block light, a lower porosity is preferable. The porosity is preferably 0.01% or more. If the porosity is less than 0.01%, the contact area with the electrolyte may decrease. In addition, it is preferable that the multi-element complex oxide powder according to the embodiment is contained in the range of 50% by mass to 100% by mass of the electrochromic layer.

[0081] FIG. 6 shows the configuration of an electrochromic element. This figure is a conceptual diagram showing another example of the structure of an electrochemical device according to an embodiment. The electrochromic element 20 shown in the figure includes an electrolyte layer 23 and a pair of electrochromic layers disposed on one main surface of the electrolyte layer 23 and the other main surface on the back side thereof. The pair of electrochromic layers includes an electrochromic layer 22 and a counter electrode 24. The electrochromic element 20 further includes a first electrode 21 disposed on the outside of the electrochromic layer 22, with the side facing the electrolyte layer 23 regarded as the inside, and a second electrode 25 disposed on the outside of the counter electrode 24. In addition, the electrochromic element 20 includes a first substrate 26 and a second substrate 27, which are a pair of substrates disposed on the outside of the first electrode 21 and the second electrode 25.

[0082] Since the electrochromic element transmits and blocks light, the first substrate 26 and the second substrate 27 are preferably transparent substrates. For example, a glass substrate can be used as the transparent substrate. The first electrode 21 is for ensuring adhesion and electrical conductivity between the first substrate 26 and the electrochromic layer 22. The second electrode 25 is for ensuring adhesion and electrical conductivity between the second substrate 27 and the counter electrode 24. An example of the electrode is an Al (aluminum) electrode. The counter electrode 24 is for carrying out an oxidation reaction (or reduction reaction) involving charge transfer. The counter electrode 24 can be, for example, IrO 2 / SnO 2The electrolyte layer 23 is for supplying and transporting ions. The electrolyte layer 23 is preferably one that does not allow electrons to pass through. An example of the electrolyte layer 23 is Ta. 2 O 5 Examples of the material include a vapor deposition film. The electrochromic layer 22 is an electrode layer containing the multi-element composite oxide powder according to the embodiment. With the combination of these materials, the element can be formed as a thin film by vapor deposition or the like. Therefore, an element with excellent mass productivity can be provided.

[0083] In an electrochromic element, when an external voltage is applied between the first electrode 21 and the second electrode 25, electrons are injected into the electrochromic layer 22 and ions are injected into the electrolyte layer 23. A phenomenon occurs in which positive ions are released into the electrolyte layer 23 or negative ions are taken in. At the same time, a phenomenon occurs in which electrons are transferred to an external power source via the first electrode 21 or the second electrode 25. These phenomena cause coloring. Furthermore, a reverse reaction occurs by applying a reverse voltage or shorting the electrodes, causing decoloration. By using transparent substrates for the first substrate 26 and the second substrate 27, the substrate becomes transparent after decolorization.

[0084] [catalyst] The multi-element composite oxide powder according to the embodiment can also be used as a catalyst. The catalyst containing the multi-element composite oxide powder can be, for example, a thermal catalyst or a photocatalyst. A photocatalyst is a substance that exhibits catalytic activity when irradiated with light. Here, a thermal catalyst refers to a typical catalyst, and unlike a photocatalyst, it exhibits catalytic activity even without irradiation with light.

[0085] An example of a reaction in which a catalyst containing such a multi-element composite oxide powder exhibits a thermal catalytic action is the reaction of oxidizing ethanol to acetaldehyde.

[0086] A photocatalyst may have the function of, for example, decomposing organic matter that comes into contact with its surface. In one specific example of a photocatalyst, when irradiated with light, the photocatalyst absorbs light to form electrons and holes. These react with moisture in the air and change into active oxygen and hydroxyl radicals, which can generate photocatalytic performance. When the photocatalytic performance is exerted, odorous components and the like can be decomposed.

[0087] The composite oxide powder may be used as a catalyst by itself. Alternatively, the form of the composite oxide may be changed depending on the environment in which it is used as a catalyst. For example, a thin layer of the composite oxide may be formed on a substrate and used as a catalyst. When used as a photocatalyst, the porosity of the thin layer is preferably 80% or less.

[0088] The above uses are examples of the multi-element composite oxide powder according to the embodiment used as a powder. The multi-element composite oxide powder according to the embodiment may be used as a bulk made from a raw material. The bulk may be a sintered body or the like. The multi-element composite oxide powder may also be used for other uses. Examples of uses other than those mentioned above include thermoelectric functional materials and dielectrics, such as thermoelectric materials.

[0089] [Example] The oxide powder was prepared as follows.

[0090] (Examples 1-7, Comparative Examples 1-2) In Examples 1-7 and Comparative Examples 1-2, oxide powders were produced according to the above-mentioned method. Specifically, first, various metal oxides as raw materials were mixed so that the ratio of metal elements was the atomic ratio shown in Table 1 below to obtain a mixed powder. The obtained mixed powder was subjected to a plasma treatment to compound the metal elements in the raw materials, and then a stable phase was extracted. The stable phase was fired in the atmosphere for 1 hour to obtain a product. In the plasma treatment, Ar and O 2 A mixed gas of 1000 nm and 1000 μm was used as the carrier gas. The stable phase was fired at the firing temperature shown in Table 1. The stable phase was extracted by a method that extracts particles of 100 nm or less. Specifically, in Examples 1-6 and Comparative Examples 1-2, the mixed powder was slurried and then subjected to plasma treatment, while in Example 7, the powder was used as it was and subjected to plasma treatment. In addition, a cyclone was used to remove particles smaller than 100 nm.

[0091] (Comparative Example 3-4) In Comparative Example 3-4, the raw material mixed powder was directly fired in the air for 1 hour without plasma treatment to produce the oxide powder. The raw material used was a mixed powder in which various metal oxides were mixed in a ratio in which the ratio of metal elements was the atomic ratio shown in Table 1. The firing was performed at the firing temperature shown in Table 1.

[0092] [Table 1]

[0093] The composition of the oxides contained in the products obtained in each of the Examples and Comparative Examples was measured by the ICP atomic emission spectroscopy and inert gas fusion-infrared absorption method described above. The measurement results and the compositions obtained from the measurement results are shown in Tables 2 and 3 below. Specifically, the ratios of the measured constituent metal elements are summarized in Table 2. Table 2 also summarizes the respective contents of hexavalent metal elements (here, W and Mo), pentavalent metal elements (here, V, Nb, and Ta), and tetravalent metal elements (here, Ti) among the constituent metal elements. Table 3 shows the composition formula of each product and each composition according to the general formula I(W a Mo b A c O z ) or general formula II (W a Mo b A e Ti f O z ) However, since comparative examples 1 and 2 produced powders of molybdenum trioxide and tungsten trioxide, respectively, which do not fit into any of the general formulas, the values ​​of the subscripts a, b, and z common to both are summarized here.

[0094] [Table 2]

[0095] [Table 3]

[0096] As can be seen from the table, there was a compositional discrepancy between the raw material mixed powder and the resulting multi-element composite oxide powder. Moreover, the multi-element composite oxide powders according to Examples 1-6 were powders of a single composition. In contrast, the oxide powder according to Example 7 was a mixed powder of powders of two different compositions. From a comparison between Examples 1-6 and 7, it can be seen that a multi-element composite oxide powder of a single composition can be easily obtained by forming a raw material powder into a slurry and subjecting it to a plasma treatment.

[0097] The oxide particles contained in the oxide powder produced in each of the Examples and Comparative Examples were observed by STEM. The shape, minor and major axis lengths, aspect ratio, and crystal structure of the oxide particles confirmed by the observation are summarized in Table 4 below. Here, with regard to the particle shape, particles with an aspect ratio of 2 or more are called "acicular", and particles with an aspect ratio of less than 2 are called "spherical". Note that particles classified as "acicular" do not necessarily have a sharp needle tip, and also include particles with a columnar or rod shape. With regard to the crystal structure, whether or not it corresponds to a crystal structure having a polygonal tunnel structure, and the presence or absence of a subphase are indicated. The presence or absence of a subphase was confirmed by scanning electron microscope-energy dispersive X-ray spectroscopy (Scanning Electron Microscope-Energy Dispersive X-ray spectroscopy). The particle was observed at a magnification of 1000 times and the metal elements that constituted it were mapped. Of the 10 acicular particles measured, 9 were found to be of the same composition. When the number of particles is more than 1, it is determined that each element is uniformly dispersed within the particle. For simplicity, it may be determined by the presence or absence of a peak of a different phase in XRD analysis.

[0098] [Table 4]

[0099] As can be seen from the table, the composite oxide powder according to the embodiment corresponds to a crystal structure having a tunnel structure. In addition, since the tunnel structure was present as a result of measurement from the long axis direction, it can also be said to have a columnar crystal structure grown in the long axis direction. In addition, since the heat treatment temperature of Example 5 was high, the long axis was large at 3000 nm (= 3 μm). Moreover, in the multi-element composite oxide powders according to Examples 1 to 7, the tetragonal phase was predominant, and no subphase was observed.

[0100] <Performance evaluation> The oxide powders produced in each of the Examples and Comparative Examples were evaluated for their performance as electrochemical functional materials for electrochemical devices and their catalytic performance. Specifically, the volume resistivity, melting point, discharge capacity, and color change rate were measured, and the catalytic performance was evaluated as follows.

[0101] (Volume Resistivity Measurement) The volume resistivity of the oxide powder was measured by the following method. The sample powder was filled with 1g to 3g. The measurement method used was the four-terminal method, and the four terminals were arranged in a straight line with an electrode interval of 3mm. The volume resistivity was measured while applying pressure of 4N (Newtons), 8N, 12N, 16N, and 20N to the sample using a hydraulic jack, and the lowest volume resistivity value was determined as the volume of the material. The resistivity was calculated as the product resistivity.

[0102] The volume resistivity determined for each of the Examples and Comparative Examples is summarized in Table 5 below. Volume resistivity is inversely proportional to electrical conductivity. Thus, a lower value of volume resistivity indicates higher electrical conductivity.

[0103] (Melt point measurement) The melting point of the oxide powder was measured by the following method. 3 g of the sample was placed in a 10 ml alumina flask with a lid. The sample was placed in a crucible and fired in an air atmosphere in a box furnace. The target temperature was held for 1 hour, and the sample was allowed to cool naturally to room temperature. The melting point was the temperature at which the sample stuck to the inside of the crucible and could no longer be removed as particles.

[0104] The melting points determined for each of the Examples and Comparative Examples are summarized in Table 5 below. The melting point is an index of thermal stability. The higher the melting point, the higher the thermal stability of the oxide. For Examples 1-5, even when the target temperature was set to 1100°C, the sample could be removed from the crucible after cooling. For these Examples 1-5, the melting point is shown as "1000°C or higher." For Comparative Example 2, the literature value is shown.

[0105] (Measurement of discharge capacity) An electricity storage device was produced using the oxide powder, and the discharge capacity of the oxide powder was measured.

[0106] The electricity storage device was fabricated as follows: The electricity storage device had the cell structure shown in FIG.

[0107] First, an electrode layer was prepared as follows. The oxide powder produced in each Example and Comparative Example was mixed with acetylene black to prepare a paste. The prepared paste was applied to a substrate, and dried and pressed to form an electrode layer. The paste was prepared by mixing 90 parts by mass of oxide powder and 10 parts by mass of acetylene black. Thus, a coating weight of 3.3 mg / cm was obtained. 2 An electrode layer having a thickness of 20 μm and a porosity of 20% was obtained.

[0108] A conductive coated aluminum foil having a thickness of 15 μm was prepared as the negative electrode layer 11 and the positive electrode layer 15. The electrode layer prepared as described above was used as the negative electrode layer 12. The positive electrode layer 14 was made of LiCoO 2 The positive electrode layer was fabricated using a powder. The coating weight of the positive electrode layer was set to an amount that was sufficient for the electrical capacity of the negative electrode layer. The electrode area of ​​both the negative and positive electrodes was φ16 mm (approximately 2 cm 2 ) was decided.

[0109] A polyethylene porous layer (thickness: 20 μm) was used for the separator layer 13. A laminate was obtained by laminating the negative electrode layer 11, the negative electrode layer 12, the separator layer 13, the positive electrode layer 14, and the positive electrode layer 15 in this order. This laminate was incorporated into an aluminum cell container. Then, the container was impregnated with an electrolytic solution, degassed, and sealed. A mixed solution of propylene carbonate (PC) and ethyl methyl carbonate (EMC) was used as the solvent for the electrolytic solution. LiPF 6 and LiBF 4 was mixed with the electrolyte solvent.

[0110] As described above, an electricity storage device was prepared. The electricity storage device was used to charge and discharge electricity under the following conditions, and the discharge capacity was measured. The charge voltage was 1.55 V and the discharge voltage was 3 V. The charge and discharge were performed at a constant current of 0.5 mA. The discharge capacity was measured during discharge. The measurement results are summarized in Table 5 below.

[0111] (Measurement of color change rate) An electrochromic device was fabricated using the oxide powder, and the color change speed was measured.

[0112] An electrochromic element having the cell structure shown in FIG. 6 was fabricated.

[0113] The electrochromic layer 22 was formed by mixing an oxide powder with an organic substance and applying the mixture to a glass substrate with an ITO film. That is, a transparent glass substrate was used as the first substrate 26, and ITO was used as the first electrode 21. In addition, Ta 2 O 5 A deposition film was used, and the counter electrode 24 was IrO 2 / SnO 2 The second substrate 27 and the second electrode 25 were made of a transparent glass substrate and an Al electrode, respectively.

[0114] The response speed of the color change caused by the application of voltage was measured for the electrochromic element thus fabricated. The response speed (s) was measured as the time (in seconds) from a colored state to a transparent state using the following method. The color change was measured using an ultraviolet-visible spectrophotometer. When a voltage of 1.2 V was applied to the electrochromic element, the time it took for the transmittance of light with a wavelength of 600 nm to change from 20% to 70% was measured. The time it took for the color change to occur was measured and recorded as the response speed. The response speeds of the color change obtained are summarized in Table 5 below.

[0115] (Evaluation of catalyst performance) The catalytic performance of the oxide powder was evaluated by measuring the efficiency of the oxidation reaction of ethanol to acetaldehyde using the oxide powder as a catalyst. Specifically, the yield of the product (acetaldehyde) in the catalytic reaction was measured.

[0116] 0.1 g of sample and SiO with a particle size of 100 nm 2 The mixture was charged into a flow reactor. The reaction temperature was set at 300°C and N was used as a carrier gas. 2 The reaction was carried out by introducing ethanol at a flow rate of 21 ml / min using a gas chromatograph. The type and amount of the product after passing through the reactor were measured by gas chromatography.

[0117] The yield was calculated from the following formula: Yield = [(measured amount of acetaldehyde) / (injected amount) (mol amount of ethanol added). The yields obtained are summarized in Table 5 below.

[0118] [Table 5]

[0119] In Examples 1-7, multi-component complex oxide powders were produced in which 80 atm% or more of the constituent metal elements were two or more hexavalent metal elements and two or more pentavalent metal elements, and which contained complex oxide particles having a polygonal tunnel structure. In contrast, in Comparative Examples 1 and 2, tungsten trioxide and molybdenum trioxide powders containing only one metal element were produced, respectively. In Comparative Examples 3 and 4, multi-component complex oxide powders were produced in which 80 atm% or more of the constituent metal elements were two or more hexavalent metal elements and two or more pentavalent metal elements, but which did not have a polygonal tunnel structure. All of the multi-component complex oxide powders according to Examples 1-6 were superior in conductivity, discharge capacity, response speed, and catalytic performance to the metal oxide powders according to Comparative Examples 1 and 2 and the multi-component complex oxide powders according to Comparative Examples 3 and 4. The multi-component complex oxide powders according to Comparative Examples 3 and 4 did not show a color change even when a voltage was applied, and did not have electrochromic performance. Moreover, the multi-element composite oxide powders according to Examples 1-7 all had higher melting points than the powders according to Comparative Examples 1, 3, and 4. On the one hand, Example 7 was superior in electrical conductivity, discharge capacity, response speed, and catalytic performance compared to the powders of Comparative Examples 1, 3, and 4. On the other hand, in Example 7, the obtained oxide powder was a mixed powder consisting of two types of compositions, and therefore the volume resistance was increased and the melting point was lower compared to Examples 1 to 6. From this, it can be seen that a multi-element composite oxide powder consisting of a single composition is preferable.

[0120] Subphases were confirmed in the oxide particles in the multi-element composite oxide powders according to Comparative Examples 3 and 4. In Comparative Examples 3 and 4, a simple mixture and firing were performed, so plasma treatment and subsequent extraction of the stable phase were not performed. Unlike Examples 1-7 in which oxides were synthesized by firing the stable phase, it is presumed that various oxide phases were generated in a mixed state in Comparative Examples 3 and 4.

[0121] According to one or more of the embodiments and examples described above, a multi-element complex oxide powder is provided. The multi-element complex oxide powder includes oxide particles containing a complex oxide. The complex oxide contains constituent metal elements containing two or more hexavalent metal elements and two or more pentavalent metal elements in a total content of 80 atm% or more, and oxygen. The oxide particles have a major axis and a minor axis intersecting with the major axis. The oxide particles have a polygonal tunnel structure including one or more polygonal tunnels having pentagons or more along the major axis direction along the major axis of the oxide particles. The multi-element complex oxide powder has high electrical conductivity and thermal stability, has a high capacity as an electricity storage material, has a high reversible reaction rate of electrochromic properties, and can exhibit high catalytic activity.

[0122] Although some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and spirit of the invention, and are included in the scope of the invention and its equivalents described in the claims. The inventions described in the original claims of the parent application of this application are set forth below. [1] A metal element containing two or more hexavalent metal elements and two or more pentavalent metal elements in a total content of 80 atm% or more; Oxygen and The oxide particles include a composite oxide containing The oxide particles have a major axis and a minor axis intersecting the major axis, and have a polygonal tunnel structure including one or more polygonal tunnels having 5 or more sides along the major axis direction along the major axis. [2] The multi-element composite oxide powder according to [1], wherein the constituent metal elements contain the hexavalent metal element and the pentavalent metal element in a total content of 90 atm % or more. [3] The multi-element composite oxide powder according to [1] or [2], wherein the constituent metal elements contain the hexavalent metal element in an amount of 40 atm % or more and 90 atm % or less. [4] The multi-element composite oxide powder according to any one of [1] to [3], wherein the constituent metal elements contain the pentavalent metal element in a content ratio of 9 atm % or more and 40 atm % or less. [5] The multi-element composite oxide powder according to any one of [1] to [4], wherein the constituent metal elements further contain one or more tetravalent metal elements in a content of 1 atm % or more. [6] The hexavalent metal element is selected from the group consisting of W, Mo, Cr, Re, and Mn. The multi-element composite oxide powder according to any one of [1] to [5], comprising at least one of the following: [7] The pentavalent metal element is two or more selected from the group consisting of Ta, Nb, and V. The multi-element composite oxide powder according to any one of [1] to [6], [8] The multi-element composite oxide powder according to any one of [1] to [7], wherein the oxide particle contains 20 to 70 of the polygonal tunnels in an area of ​​5 nm x 5 nm in a region not including the surrounding area up to 1 nm wide from the outer periphery on the plane intersecting the major axis direction. [9] The multi-element composite oxide powder according to any one of [1] to [8], wherein the composite oxide has a columnar crystal structure grown in the c-axis direction.

[10] The multi-element composite oxide powder according to any one of [1] to [9], wherein the aspect ratio of the major axis to the minor axis is 2 or more and 50 or less.

[11] The hexavalent metal element includes W and Mo, and the Mo element content A Mo W element content A W Ratio of A Mo / A W is 0.5≦A Mo / A W Any one of [1] to

[10] that is ≦2.5 The multi-element composite oxide powder according to any one of the preceding claims.

[12] The composite oxide has the general formula W a Mo b Ax Ti y O z In the general formula, A is 2 or more selected from the group consisting of V, Ta, and Nb, and 0.5≦a / b≦2.5, 0.4≦a+b≦0.9, 0.09≦x≦0.6, 0≦y≦0.3, 2≦z≦3, and a+b+x+y=1. The multi-element composite oxide powder according to any one of [1] to

[11] .

[13] An electrochemical device comprising the multi-element composite oxide powder according to any one of [1] to

[12] as an electrochemical functional material.

[14] A catalyst comprising the multi-element composite oxide powder according to any one of [1] to

[12] .

[15] Mixing oxides of the constituent metal elements to obtain a mixed powder; subjecting the mixed powder to a plasma treatment; Removing the stable phase after the plasma treatment; obtaining the composite oxide by heat-treating the stable phase in an oxygen-containing atmosphere;

[13] A method for producing a multi-element composite oxide powder, comprising: producing the multi-element composite oxide powder according to any one of [1] to

[12] .

[16] In the plasma treatment, N 2 and O 2 or Ar and O 2 The method for producing a multi-element composite oxide powder according to

[15] , wherein a mixed gas of

[17] The method for producing a multi-element composite oxide powder according to

[15] or

[16] , wherein extracting the stable phase includes sieving and removing coarse particles having a particle size of 1 μm or more. [Explanation of symbols]

[0123] 1...oxide particle, 2...side, 3...face, 3a...region, 3b...surrounding portion, 4...square tunnel, 5...pentagonal tunnel, 6...hexagonal tunnel, 8...layer, 9...metal atom, 10...energy storage device, 11...negative electrode layer, 12...negative electrode layer, 13...separator layer, 14...positive electrode layer, 15...positive electrode layer, 20...electrochromic element, 21...first electrode, 22...electrochromic layer, 23...electrolyte layer, 24...counter electrode, 25...second electrode, 26...first substrate, 27...second substrate.

Claims

1. A composition comprising two hexavalent metal elements and two or more pentavalent metal elements in a total content of 80 atm% or more; Oxygen and The hexavalent metal element is contained in a total amount of 40 atm% or more and 90 atm% or less, the hexavalent metal element is composed of W and Mo, the pentavalent metal element is contained in a total amount of 9 atm% or more and 40 atm% or less, and the pentavalent metal element includes oxide particles containing a composite oxide composed of two or more elements selected from the group consisting of Ta, Nb, and V, The oxide particles have a major axis and a minor axis intersecting the major axis, and have a polygonal tunnel structure including one or more polygonal tunnels having 5 or more sides along the major axis direction along the major axis.

2. 2. The multi-component composite oxide powder according to claim 1, wherein the constituent metal elements contain the hexavalent metal element and the pentavalent metal element in a total content of 90 atm % or more.

3. 3. The multi-element composite oxide powder according to claim 1, wherein the constituent metal elements further contain one or more tetravalent metal elements in a content of 1 atm % or more.

4. 3. The multi-element composite oxide powder according to claim 1, wherein the oxide particle includes 20 to 70 of the polygonal tunnels in an area of ​​5 nm x 5 nm in a region not including a peripheral portion up to 1 nm wide from the outer periphery in a plane intersecting the major axis direction.

5. 3. The multi-element composite oxide powder according to claim 1, wherein the composite oxide has a columnar crystal structure grown in a long axis direction.

6. 3. The multi-element composite oxide powder according to claim 1, wherein an aspect ratio of the major axis to the minor axis is 2 or more and 50 or less.

7. Mo element content A Mo W element content A W Ratio A W / A Mo is 0.5≦A W / A Mo 3. The multi-element composite oxide powder according to claim 1 or 2, wherein the Mn content is ≦2.

5.

8. The composite oxide has the general formula W a Mo b A x Ti y O z wherein in the general formula, A is 2 or more selected from the group consisting of V, Ta, and Nb, and 0.5≦a / b≦2.5, 0.4≦a+b≦0.9, 0.09≦x≦0.6, 0≦y≦0.3, 2≦z≦3, and a+b+x+y=1.

9. The composite oxide has the general formula W a Mo b A x Ti y O z wherein in the general formula, A is 2 or more selected from the group consisting of V, Ta, and Nb, 0.5≦a / b≦2.5, 0.4≦a+b≦0.9, 0.09≦x≦0.6, 0≦y≦0.3, 2≦z≦3, and a+b+x+y=1; and an aspect ratio of the major axis to the minor axis is 2 or more and 50 or less.

10. Mo element content A Mo W element content A W Ratio A W / A Mo is 0.5≦A W / A Mo ≦2.5, and the composite oxide is represented by the general formula W a Mo b A x Ti y O z wherein in the general formula, A is 2 or more selected from the group consisting of V, Ta, and Nb, 0.5≦a / b≦2.5, 0.4≦a+b≦0.9, 0.09≦x≦0.6, 0≦y≦0.3, 2≦z≦3, and a+b+x+y=1; the oxide particle includes 20 to 70 of the polygonal tunnels in an area of ​​5 nm × 5 nm in a region not including a peripheral portion up to 1 nm wide from the outer periphery in a plane intersecting with the major axis direction, and an aspect ratio of the major axis to the minor axis is 2 or more and 50 or less.

11. 3. An electrochemical device comprising the multi-element composite oxide powder according to claim 1 or 2 as an electrochemical functional material.

12. A catalyst comprising the multi-element composite oxide powder according to claim 1 or 2.

13. mixing oxides of the constituent metal elements to obtain a mixed powder; subjecting the mixed powder to a plasma treatment; Removing the stable phase after the plasma treatment; obtaining the composite oxide by heat-treating the stable phase in an oxygen-containing atmosphere; A method for producing a multi-element composite oxide powder, comprising:

14. In the plasma treatment, N 2 and O 2 or Ar and O 2 The method for producing a multi-element composite oxide powder according to claim 13, wherein a mixed gas of

15. 14. The method for producing a multi-element composite oxide powder according to claim 13, wherein the step of extracting the stable phase includes removing coarse particles having a particle size of 1 μm or more by sieving or cyclone treatment.

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