WO2009116378A1 - SOLID TRANSITION METAL HYDROXIDE FILM, α-COBALT HYDROXIDE FILM, MANUFACTURING METHOD FOR SOLID TRANSITION METAL HYDROXIDE, MANUFACTURING METHOD FOR α-COBALT HYDROXIDE, MANUFACTURING DEVICE FOR SOLID TRANSITION METAL HYDROXIDE, MANUFACTURING METHOD FOR TRANSITION METAL HYDROXIDE, MANUFACTURING METHOD FOR HYDRATED LITHIUM COBALT OXIDE, TRANSITION METAL OXIDE FILM, AND ELECTRODE MATERIAL - Google Patents

Abstract

Provided is a transition metal hydroxide film or the like with a controlled alignment. An aspect of the invention is an α-cobalt hydroxide film formed on a substrate, wherein the α-cobalt hydroxide is characterized in that the c axis of the α-cobalt hydroxide is roughly perpendicular to the substrate surface. The configuration makes it possible to obtain an α-cobalt hydroxide film with a controlled alignment and the material obtained may be expected to have various improved characteristics. Another aspect of the invention is a manufacturing method of α-cobalt hydroxide characterized in that α-cobalt hydroxide is formed while raising pH by mixing ammonia gas into a cobalt ion solution. The configuration makes it possible to obtain α-cobalt hydroxide easily.

Description

Solid transition metal hydroxide film, α-type cobalt hydroxide film, solid transition metal hydroxide production method, α-type cobalt hydroxide production method, solid transition metal hydroxide production apparatus, transition metal oxide production method, water Method for producing Japanese lithium cobalt oxide, transition metal oxide film, cobalt oxide film, and electrode material

The present invention relates to a solid transition metal hydroxide, in particular, a solid transition metal hydroxide film, an α-type cobalt hydroxide film, a solid transition metal hydroxide production method, an α-type cobalt hydroxide production method, an electrode material, and The present invention relates to a solid transition metal hydroxide production apparatus.

In recent years, research on nickel-hydrogen batteries and lithium ion secondary batteries as next-generation energy devices has been actively conducted both academically and industrially. Accordingly, transition metal hydroxides are attracting attention as one of electrode materials. Nickel hydroxide is expected as an electrode material for nickel-hydrogen batteries, and cobalt hydroxide is expected as a material that contributes to improving the characteristics of lithium ion secondary batteries.

Among these compounds, crystals with α-type crystal structure, which is metastable phase, are expected to be used for these electrode materials. Is considered difficult to synthesize. It is not a thermodynamically stable crystal phase, and a β-type structure can be obtained directly without passing through this α-type (Non-patent Document 1), or a transition to β-type occurs due to aging during synthesis or after production. There are many cases in general.

On the other hand, there are reports of synthesis using temperatures near 100 ° C. and electrode reactions, but in addition to the need for special equipment, in many cases the crystallinity is low and the controllability of the structure is poor. There is a problem. To a method and substrate for selectively synthesizing and controlling the transition metal hydroxide having both the α-type crystal structure and high crystallinity in a low-temperature, simple and low-cost process without requiring a special apparatus. A method for thinning the film has not been developed.

In addition, α-type has been suggested to show better electrochemical characteristics than β-type when used for lithium ion battery electrodes and electrochemical capacitors, but the effects of crystallinity and structure are studied. Since it has not been completed, it is difficult to say that the investigation of electrochemical characteristics utilizing the α-type structure is sufficient.

For example, α-type selective synthesis is performed by mixing an aqueous solution containing ammonium ions and an aqueous solution containing cobalt ions (Non-patent Document 2), an electrochemical technique (Non-patent Document 3), or the like. However, the crystallinity is not good. The poor crystallinity is often caused by the disordered layered structure. The α-type selective synthesis is obtained by decomposing hexamethylenetetramine in the presence of sodium chloride in an aqueous solution containing cobalt ions, but requires a temperature of 90 ° C, and it has not been thinned. No (non-patent document 4). Similarly, a production example using decomposition of urea is also shown (Non-Patent Documents 5 and 6), but it is merely an aggregate of plate crystals and is hardly a thin film material.

In general, the thermodynamically most stable β-type has a small interlayer distance (about 0.46 nm or less) and a laminated structure of layers represented by a stoichiometric ratio of Co (OH) ₂ . On the other hand, in the α-type, negatively charged layers represented by Co (OH) _2-x are stacked with an interlayer distance of about 0.8 nm or more. In layered compounds other than cobalt-based materials, research on optical functionalization using interlayers is often conducted, but in cobalt-based materials, there are not many reports on functionalization between layers except for research on magnetism (Non-patent Document 7). .

The present invention has been made in view of the above-described background art, and an object thereof is to provide a transition metal hydroxide film having controlled orientation.

According to this invention, in order to achieve the above-mentioned object, the configuration as described in the claims is adopted. Hereinafter, the present invention will be described in detail.

The first aspect of the present invention is:
A transition metal hydroxide film formed on a substrate,
In the transition metal hydroxide film, the crystal axis of the transition metal hydroxide film is oriented with respect to the surface of the substrate.

According to this configuration, a transition metal hydroxide film with controlled orientation can be obtained, and a material that can be expected to improve various characteristics can be obtained.

The second aspect of the present invention is
2. The transition metal hydroxide film according to claim 1, wherein the transition metal is any one of Zn, Cu, Ni, Mn, and Co. The transition metal may be a multi-element system including a plurality of these elements. This is the same in the following.

The third aspect of the present invention is
An α-type cobalt hydroxide film formed on a substrate,
The α-type cobalt hydroxide film is characterized in that the c-axis of α-type cobalt hydroxide is oriented with respect to the surface of the substrate.

According to this configuration, an α-type cobalt hydroxide film with controlled orientation can be obtained, and a material that can be expected to improve various characteristics can be obtained.

The fourth aspect of the present invention is
2. The α-type cobalt hydroxide film according to claim 1, wherein molecules different from α-type cobalt hydroxide are introduced between layers of α-type cobalt hydroxide.

According to this configuration, a material that enables construction of a composite material or the like can be obtained by intercalating molecules different from α-type cobalt hydroxide.

The fifth aspect of the present invention provides
An α-type cobalt hydroxide film formed on a substrate,
In the X-ray diffraction, the α-type cobalt hydroxide film is characterized in that diffraction peaks derived from the (003) plane, the (006) plane, and the (00.15) plane are observed.

According to this configuration, an α-type cobalt hydroxide film excellent in crystallinity and oriented on the base material can be obtained, and a material that can be expected to improve various characteristics is obtained.

The sixth aspect of the present invention provides
Solid transition by hydroxylating the transition metal while increasing the pH of the solution while coordinating a substance having a functional group that coordinates with the transition metal, which is different from the hydroxy group, with the transition metal in the solution A method for producing a solid transition metal hydroxide is characterized in that a metal hydroxide is formed.

According to this configuration, a gentle crystal growth environment is realized, and a solid transition metal hydroxide having high crystallinity can be obtained.

The seventh aspect of the present invention provides
7. The solid transition metal hydroxide manufacturing method according to claim 6, wherein the transition metal is any one of Zn, Cu, Ni, Mn, and Co.

The eighth aspect of the present invention is
7. The method for producing a solid transition metal hydroxide according to claim 6, wherein the substance having a functional group coordinated with the transition metal is a volatile base.
It is in.

The ninth aspect of the present invention provides
7. The method for producing a solid transition metal hydroxide according to claim 6, wherein the substance having a functional group coordinated with the transition metal is ammonia.
It is in.

The tenth aspect of the present invention provides
7. The transition metal solution according to claim 6, wherein a molecule that intercalates between layers of a solid transition metal hydroxide is added, and the molecules are intercalated between layers of a solid transition metal hydroxide. It exists in the manufacturing method of a solid transition metal hydroxide.

According to this configuration, a material capable of constructing a composite material or the like can be obtained by intercalating molecules.
It is in.

The eleventh aspect of the present invention is
An α-type cobalt hydroxide production method is characterized in that α-type cobalt hydroxide is formed while raising pH by dissolving a volatile base gas in a cobalt ion solution.

According to this configuration, α-type cobalt hydroxide can be obtained by a simple method.

The twelfth aspect of the present invention is
12. The method for producing α-type cobalt hydroxide according to claim 11, wherein a molecule having a functional group coordinated with cobalt ions is added to the cobalt ion solution.

According to this configuration, α-type cobalt hydroxide having a controlled shape is obtained. An example of a molecule having a functional group coordinated with cobalt ion is polyacrylic acid.

The thirteenth aspect of the present invention is
12. The method for producing α-type cobalt hydroxide according to claim 11, wherein the substrate is immersed in the cobalt ion solution to form α-type cobalt hydroxide on the substrate.

According to this configuration, α-type cobalt hydroxide can be deposited on the substrate.

The fourteenth aspect of the present invention provides
12. The method for producing α-type cobalt hydroxide according to claim 11, wherein a functional group that coordinates with cobalt ions is present on the surface of the substrate.

According to this configuration, oriented α-type cobalt hydroxide having high crystallinity can be obtained. Examples of functional groups that coordinate with cobalt ions include amino groups.

The fifteenth aspect of the present invention is
12. The α type according to claim 11, wherein a molecule that intercalates between layers of α-type cobalt hydroxide is added to the cobalt ion solution, and the molecules are intercalated between layers of α-type cobalt hydroxide. It is in the manufacturing method of cobalt hydroxide.

According to this configuration, a material capable of constructing a composite material or the like can be obtained by intercalating molecules.

The sixteenth aspect of the present invention is
A solid transition metal hydroxide production method is characterized in that a volatile base gas is gradually dissolved in a transition metal solution to form a solid transition metal hydroxide.

According to this configuration, a gentle crystal growth environment is realized, and a solid transition metal hydroxide having high crystallinity can be obtained.

The seventeenth aspect of the present invention is
Storing the first container containing the transition metal solution and the second container containing the volatile base solution together in the third container;
Solid transition having a step of increasing the pH of the solution in the first container by diffusing the volatile base gas volatilized from the second container into the third container and dissolving in the solution in the first container It is in the metal hydroxide manufacturing method.

According to this configuration, it is possible to obtain a solid transition metal hydroxide by a simple method.

The eighteenth aspect of the present invention provides
Storing both the first container containing the cobalt ion solution and the second container containing the ammonia solution in the third container;
A step of increasing the pH of the solution in the first container by diffusing ammonia gas volatilized from the second container into the third container and dissolving in the solution in the first container. It is in the manufacturing method of cobalt oxide.

According to this configuration, α-type cobalt hydroxide can be obtained by a simple method.

The nineteenth aspect of the present invention provides
A gas container containing polyacrylic acid and cobalt ion solution to be intercalated, and the first container in which the substrate is immersed and the second container in which the ammonia solution is contained are housed in a sealed container, and the ammonia gas volatilized from the ammonia solution. Diffusing in a sealed container;
And increasing the pH of the cobalt ion solution by dissolving the ammonia gas in the cobalt ion solution,
An α-type cobalt hydroxide manufacturing method is characterized in that an α-type cobalt hydroxide having molecules intercalated between layers of α-type cobalt hydroxide is formed on a substrate.

According to this configuration, α-type cobalt hydroxide having high crystallinity can be obtained.

The twentieth aspect of the present invention provides
Means for holding a transition metal solution;
Means for dissolving volatile base gas in the transition metal solution,
The volatile base gas dissolves in the transition metal solution to form a solid transition metal hydroxide while raising the pH, and thus the solid transition metal hydroxide production apparatus is characterized.

According to this configuration, it is possible to obtain a solid transition metal hydroxide by a simple method.

The 21st aspect of the present invention is
Having a step of reacting a transition metal hydroxide with hypochlorite ion,
The transition metal is any one of Ni and Co in the method for producing a transition metal oxide.

According to this configuration, it is possible to obtain a transition metal oxide by a simple method. The transition metal may be a multi-element system including a plurality of these elements. This is the same in the following.

The twenty-second aspect of the present invention provides
22. The method for producing a transition metal oxide according to claim 21, wherein the transition metal hydroxide is reacted with hypochlorite ions in the presence of an alkali ion source.

According to this configuration, it is possible to obtain a transition metal oxide into which alkali ions are introduced by a simple method.

The twenty-third aspect of the present invention provides
22. The method for producing a transition metal oxide according to claim 21, wherein the transition metal is Co.

According to this configuration, a cobalt oxide can be obtained by a simple method.

The twenty-fourth aspect of the present invention provides
24. The method for producing a transition metal oxide according to claim 23, wherein the transition metal hydroxide is α-type cobalt hydroxide.

According to this configuration, a cobalt oxide can be obtained by a simple method.

The 25th aspect of the present invention is
24. The method for producing a transition metal oxide according to claim 23, wherein the transition metal hydroxide is α-type cobalt hydroxide crystal.

According to this configuration, it is possible to obtain a cobalt oxide whose crystal orientation is controlled by a simple method.

The twenty-sixth aspect of the present invention provides
A step of reacting a transition metal hydroxide film formed on a substrate and having a crystallographic axis of the transition metal hydroxide film oriented with respect to the surface of the substrate with hypochlorite ions;
The transition metal is any one of Ni and Co in the method for producing a transition metal oxide film.

According to this configuration, it is possible to obtain a transition metal oxide film while maintaining the orientation.

The twenty-seventh aspect of the present invention provides
Forming a transition metal hydroxide by dissolving volatile base gas in the transition metal solution;
Reacting the transition metal hydroxide with hypochlorite ions,
The transition metal is any one of Ni and Co in the method for producing a transition metal oxide.

According to this configuration, it is possible to obtain a transition metal oxide by a simple method.

The 28th aspect of the present invention provides
The first container containing the polyacrylic acid and cobalt ion solution and the substrate immersed therein and the second container containing the ammonia solution are both housed in a sealed container, and the ammonia gas volatilized from the ammonia solution is diffused into the sealed container. A process of
Increasing the pH of the cobalt ion solution by dissolving the ammonia gas in the cobalt ion solution, and forming α-type cobalt hydroxide on the substrate;
And immersing the α-type cobalt hydroxide in a solution in which lithium ions and hypochlorite ions are dissolved.

According to this configuration, a cobalt oxide can be obtained by a simple method.

The 29th aspect of the present invention provides
A transition metal oxide film formed on a substrate,
In the transition metal oxide film, the crystal axis of the transition metal hydroxide film is oriented with respect to the surface of the substrate.

According to this configuration, a transition metal oxide film with controlled orientation can be obtained, and a material that can be expected to improve various characteristics can be obtained.

The thirtieth aspect of the present invention is
30. The transition metal oxide film according to claim 29, wherein the transition metal is one of Ni and Co.

According to this configuration, a transition metal oxide film with controlled orientation can be obtained, and a material that can be expected to improve various characteristics can be obtained.

The thirty-first aspect of the present invention provides
A cobalt oxide film formed on a substrate,
In the cobalt oxide film, the c-axis of the cobalt oxide film is oriented with respect to the surface of the substrate.

According to this configuration, a cobalt oxide film with controlled orientation can be obtained, and a material that can be expected to improve various characteristics can be obtained.

The thirty-second aspect of the present invention provides
32. The cobalt oxide film according to claim 31, wherein an alkali metal is introduced between the cobalt oxide layers.

According to this configuration, a cobalt oxide film in which an alkali metal is introduced and the orientation is controlled can be obtained, and a material that can be expected to improve various characteristics is obtained.

The thirty-third aspect of the present invention provides
The solid transition metal hydroxide production method or α-type cobalt hydroxide production method according to any one of claims 6 to 19, or the transition metal oxidation according to any one of claims 21 to 28. An electronic material manufactured by a method for manufacturing a product or a method for manufacturing a hydrated lithium cobalt oxide.

The functional group that coordinates with the cobalt ion is a functional group that has relatively hard properties as a Lewis base, and examples thereof include an amino group, a nitric acid group, a sulfuric acid group, and a carboxyl group.

Examples of the substance having a functional group coordinated with a transition metal or the substance having a functional group coordinated with a cobalt ion include a sulfate ion and a chelating agent. A technique of stabilizing a cobalt ion or the like with a ligand using a sulfate ion or a chelating agent and adding a base (OH ⁻ ) can be considered.

As the volatile base, a base that becomes a gas and dissolves in water, more preferably a base that generates ammonium ions (for example, ammonia, ammonia gas, volatile amine, ammonium carbonate, hydrazine (H ₂ N-NH ₂ ) derivative, etc.) ) Is an example.

As the reaction solvent, not only water but also other solvents such as alcohol are conceivable.

The transition metal hydroxide includes not only hydroxide ions but also a case where a raw material anion (anion) species (for example, a raw material chloride) or dissolved carbonic acid is incorporated. For example, cobalt hydroxide is expressed as Co (OH) _2-x (x is a number smaller than 2 and greater than or equal to 0), and this includes raw material anion (anion) species (for example, raw material chloride) and because sometimes such carbonate are dissolved, is _{incorporated, Co (OH) 2-x} -2y (A) x (CO 3) y · nH 2 O (A is the anionic species, 0 ≦ x ≦ 1,0 ≦ y ≦ 1, n is an arbitrary number) (for example, Co (OH) _2−x−2y Cl _x (CO ₃ ) _y · nH ₂ O (x−2y is a number smaller than 2 and greater than or equal to 0)). In addition, α-type cobalt hydroxide is a cobalt hydroxide having a crystal structure in which the interlayer distance is wider than that of β-type cobalt hydroxide in a layered laminated structure. Here, it is considered that any anion species may be used as a raw material, and examples thereof include sulfate ions and nitrate ions in addition to chlorine ions.

Further, the hydroxide produced by the above-described method is further reacted and converted into another compound while intercalated, and the ion exchange of the intercalated compound into another compound is performed. Is possible. In particular, it has been found that the former method can enhance the functionality of the interlayer. By this method, development to functionalization such as construction of a composite ionic conductor is possible.

According to the present invention, a transition metal hydroxide film with controlled orientation can be obtained.

Other objects, features, or advantages of the present invention will become apparent from the detailed description based on the embodiments of the present invention described later and the accompanying drawings.

It is a figure which shows the electron micrograph (a, b) and X-ray diffraction (XRD) measurement result (c) of the plate-like crystal of α-Co (OH) ₂ obtained by the method of the present embodiment. FIG. 6 is an electron micrograph relating to thinning and structural control of the obtained α-Co (OH) ₂ . It is the schematic of the preparation methods of alpha type cobalt hydroxide. 1 shows a crystal structure of cobalt hydroxide composed of {CoO ₆ } octahedral clusters, (a) a crystal structure projected from the c-axis direction (a layered structure viewed from above), and (b) perpendicular to the c-axis. It is the figure projected from various directions (viewed from the direction of the layered structure). It is a figure which shows the electron micrograph and XRD measurement result of the obtained precipitation powder. It is a figure which shows the electron micrograph of the obtained thin film, and a XRD measurement result. It is a figure which shows the electron micrograph of the obtained thin film, and a XRD measurement result. (A, b) The electron micrograph of the thin film on a chitosan matrix, (c, d) The electron micrograph of the thin film on a polyaniline matrix regarding the alpha type cobalt hydroxide crystal thin film obtained in the presence of polyacrylic acid. It is an X-ray diffraction pattern (a) of an α-type cobalt hydroxide crystal thin film obtained in the presence of polyacrylic acid, a transmission electron microscope image (b) of a part of the thin film, and an electron diffraction pattern (c) thereof. It is an X-ray-diffraction pattern which shows the behavior of intercalation, and is a figure which shows the measurement result before the intercalation (A) and after the intercalation of thiophene-3 acetic acid (B). Scanning electron micrographs of the obtained cobalt oxide plate crystals (powder sample) (a) treatment with NaClO solution (after drying), b) treatment with NaClO solution and LiOH. It is a transmission electron micrograph which shows the nanostructure of the obtained cobalt oxide plate-like crystal (powder sample). X-ray diffraction patterns of cobalt oxide plate crystals (powder sample) by various treatments (a) Treatment with NaClO solution (before drying), b) Treatment with NaClO solution (after drying), c) Treatment with NaClO solution and NaOH, d) Treatment with NaClO solution and LiOH). It is the scanning electron micrograph of the obtained cobalt oxide plate crystal (thin film sample) (a) Cobalt oxide nanosheet alignment thin film, b) Cobalt oxide plate crystal alignment thin film). X-ray diffraction pattern of cobalt oxide plate crystals (thin film sample) by various treatments (a) treatment with NaClO solution (after drying), b) treatment with ONaClO solution and NaOH, c) treatment with NaClO solution and LiOH) .

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[Overview]

The inventors of the present invention succeeded in selective synthesis and thinning of highly crystalline transition metal hydroxide having an α-type structure as a result of sincere research. First, the outline will be described.

FIG. 1 is a diagram showing an electron micrograph (a, b) and an X-ray diffraction (XRD) measurement result (c) of a plate crystal of α-Co (OH) ₂ obtained by the method of the present embodiment. . As shown in the figure, plate-like crystals of α-type cobalt hydroxide (α-Co (OH) ₂ ) having a thickness of about 50 nanometers and a size of several micrometers were selectively obtained. All XRD peaks can be attributed to α-Co (OH) ₂ , and precipitation of other crystal forms cannot be confirmed.

FIG. 2 is an electron micrograph relating to thinning and structural control of the obtained α-Co (OH) ₂ . In the figure, (a) Precipitation on glass slide, (b) Precipitation on polymer matrix, (c) Structure control to nanosheets by adding water-soluble polymer during deposition on polymer matrix An example is shown. As shown in the figure, α-Co (OH) ₂ crystals can be deposited on the base material (or substrate) by immersing the base material (or substrate) coated with glass or polymer. became. It was also found that these can all be produced by a reaction in an aqueous solution at room temperature, and the thickness and shape can be controlled by the coexisting organic polymer.

In this embodiment, a reaction is caused by diffusion and dissolution of ammonia gas by allowing a metal (cobalt / nickel) chloride aqueous solution and two reaction solutions containing ammonia water to coexist in a sealed container. By this method, unlike the method of directly mixing two liquids, while suppressing the rapid reaction and transition to a stable phase, a precipitated powder having a α-type structure that is a metastable phase and high crystallinity and This makes it possible to form a thin film directly on the substrate.

The method of the present embodiment can provide a technique that can easily produce a transition metal hydroxide having both an α-type crystal structure and high crystallinity, which has been difficult to produce. Moreover, this embodiment opens the possibility as a new electrode material by performing the structure control according to a demand.

In the following, α-type cobalt hydroxide will be described as an example, but similar results have been obtained with manganese hydroxide by the same method. In the case of other transition metal hydroxides such as Zn, Cu, Ni, etc. However, the same method can be applied. In the case of transition metal hydroxides, α-type and α-type structures often have a similar interlayer distance.

[Production method of α-type cobalt hydroxide]

FIG. 3 is a schematic view of a method for producing α-type cobalt hydroxide. In the figure, insoluble matrices represent a base material, and soluble additive represents an additive as a structure control agent.

The outline of the manufacturing process is as follows. An aqueous solution containing cobalt ions of a certain concentration (for example, about 10-50 mM cobalt chloride aqueous solution) is placed in an airtight container together with ammonia water (about 1-30 wt .-%) for several hours at room temperature (25 ° C). Leave for about 1 to 3 hours. With the volatilization of ammonia, the pH of the aqueous solution containing cobalt ions increased, and cobalt hydroxide was generated. The resulting precipitate is collected by centrifugation or filtration and dried. When depositing on the substrate, the substrate (for example, a substrate coated with a slide glass and the following organic substances: chitosan, polyaniline, polyvinyl alcohol, chitin) is immersed in the initial cobalt chloride aqueous solution. After the deposition, the deposited film is obtained by washing the substrate with water. In order to control the thickness of the precipitated cobalt hydroxide, polyacrylic acid (for example, molecular weight 2,000, 1.5 × 10 ⁻³ wt .-%) is added to the first aqueous solution containing cobalt ions.

Subsequently, an example of an actual manufacturing process will be described. First, both an aqueous solution containing a predetermined concentration of cobalt ions and ammonia water prepared in another sample tube were placed in one sealed container and allowed to stand at 25 ° C. for 3 hours. Ammonia vapor diffused and dissolved in an aqueous solution containing cobalt ions, so that the pH increased and cobalt hydroxide precipitated. The resulting precipitate was then collected by centrifugation or filtration and dried. When performing precipitation to a base material, the base material was immersed in the aqueous solution containing a cobalt ion. The shape and thickness of the precipitated cobalt hydroxide were controlled by dissolving polyacrylic acid (average molecular weight 2000) in the first aqueous solution containing cobalt ions. Furthermore, introduction (intercalation) of organic molecules between layers was performed by dissolving anionic molecules having a carboxyl group in advance in an aqueous solution containing cobalt ions. The crystal structure and crystallinity of the product were confirmed by powder X-ray diffraction (XRD), and the intercalation behavior was analyzed from the shift of the peak position indicating the interlayer distance.

Next, conditions and the like will be described in detail.

Cobalt chloride hexahydrate (CoCl ₂ · 6H ₂ O) was used as the aqueous solution containing cobalt ions, but the raw material that supplies cobalt ions is the type of counter anion for cobalt, such as nitrate, sulfate, and acetate. Can be anything. However, these counter-anions are thought to remain in and between the cobalt hydroxide crystals of the product, including chloride ions, and the exact structural formula and composition of the product will change even if the basic crystal structure remains unchanged. Come (see (6) below). In general, chloride is considered to be most preferable for use in the present invention because it can be predicted that the degree of dissociation from the metal cation is large and the influence of mixing with the product is relatively small.

Concentration conditions were performed using two sample containers containing 20 mL of 10 to 50 mM cobalt chloride aqueous solution. 2 mM to 500 mM is a preferred concentration of the aqueous cobalt chloride solution. This is because a gentle crystal growth environment with low supersaturation is realized, and if it is lower, the reaction time becomes longer, and if it is higher, crystallinity may be lowered due to high supersaturation. It is done. Moreover, in a certain concentration range (10 mM to 50 mM), both α-type cobalt hydroxide precipitates and thin films can be obtained, but higher crystallinity precipitates are obtained, and the orientation is controlled. In order to obtain a thin film, it is known that 10 mM to 20 mM is a more preferable concentration range. In addition, it is thought that the quantity of cobalt ion in a container can be arbitrarily set in consideration of the density | concentration and quantity of ammonia.

It is very preferable to raise pH by gradually diffusing ammonia gas and gradually dissolving it in a solution containing cobalt ions. Since ammonia is slowly supplied via the gas phase, the pH rises slowly, and ammonium ions generated in the solution are coordinated to cobalt ions, which suppresses the formation of abrupt precipitates and low supersaturation. It is presumed that a metastable crystal growth environment can be realized and a metastable phase can be generated.

The concentration of ammonia is preferably from 1 wt% to 28 wt% (the highest concentration of the stock solution available, if higher than this is possible), more preferably about 2 wt% to 5 wt%. Is considered to be the same as in the case of the cobalt ion (problem of supersaturation).

Here, as an example, the concentration was performed in the presence of about 10 mL of ammonia water of 2 wt .-% to 28 wt .-% (stock solution of a commercial aqueous solution). It is considered that the same result will be obtained even if it is outside this range.

Experiments are performed at temperatures around room temperature, and similar results are expected when the temperature is about 10 to 35 ° C. The ability to produce α-type cobalt hydroxide even near room temperature is a major factor that can be easily produced, and is one of the advantages of this embodiment.

Although depending on the concentration of cobalt ions and ammonia, an α-type precipitate or thin film can be obtained if it is taken out in about 3 days from the time when a green precipitate is visible in the reaction vessel, more preferably 3 to 15 hours. It is good to take it out to the extent. If the length is shorter than this, the amount of precipitation in both the precipitate and the thin film is small, and if it is longer than this, the precipitation is not a problem, but there is a concern that the amount of precipitation in the film increases and the orientation deteriorates. In particular, in order to obtain an oriented thin film, it is preferable to take it out in about 3 hours after the reaction starts. Even when it is taken out after 3 hours or more, the orientation is somewhat disturbed, but a thin film can be obtained. A blue-green precipitate characteristic of α-type can be visually confirmed about 20 minutes after the start of the reaction, and there is no significant change in the crystal structure, crystallinity, shape, etc. of the powder obtained at any time.

The basic crystal structure is as shown in FIG. 1 and there is no problem expressed as cobalt hydroxide. However, since the raw material chloride and dissolved carbonic acid are incorporated, it is precisely Co (OH) _{2 -x-2y} Cl _x (CO ₃ ) _y · nH ₂ O

For example, a thin film on a glass substrate and a substrate coated with chitosan, polyaniline, polyvinyl alcohol, chitin, etc. has already been successfully achieved. Among these, chitosan / chitin / polyaniline could give high orientation, and slide glass / polyvinyl alcohol could not provide a thin film with high orientation. Even if it is a base material other than the above, if the reaction conditions are optimized in the method of the present invention, it can be expected that a thin film can be directly formed on a desired base material by heterogeneous nucleation.

Here, the reaction was performed using polyacrylic acid as an example. Any polymer having a functional group coordinated with cobalt ions is expected to be not limited to polyacrylic acid. Examples thereof include a polymer having a carboxyl group, polycarboxylic acid, polyamine, and polysulfonic acid. However, since the monomer intercalates between layers as shown below, a polymer is more preferable for use for the purpose of shape control.

Although it seems that there is a correlation with the concentration of cobalt ions and ammonia and the reaction time, the concentration of polyacrylic acid is suitably about 0.1 to 0.5 times the cobalt ion concentration, more preferably 0. About 2 times. The polyacrylic acid concentration at this time is converted by the carboxyl group concentration (= monomer concentration). If the concentration is lower than this, the role as a control agent does not appear, and it can be expected that the crystal precipitation is suppressed in a concentration region higher than this.

Until now, there has been an attempt to introduce long-chain alkylcarboxylic acid, sulfuric acid, and cyanic acid between layers of α-type structure by another method (method of pouring ammonia water directly into an aqueous solution in which cobalt ions are dissolved). (Non-Patent Document 7). Intercalation can be interpreted as an electrostatic interaction between the positive charge between the layers and the negative charge of the molecules to be introduced.

In this embodiment, in addition to the aliphatic carboxylic acid as described above, a carboxylic acid having a functional site such as an aromatic ring or a π-conjugated system in the skeleton structure can be intercalated. Examples include molecules in which a carboxyl group is introduced into a thiophene, imidazole, or pyridine skeleton, and a shift in the interlayer distance according to the size of the molecule was confirmed by XRD. By intercalating molecules with these functional sites, it is possible to construct optical / electronic functional composite materials. The skeleton structure of the functional site can be other aromatic rings or π-conjugated systems, and it is preferable that a functional group having a negative charge (such as a sulfate group or a nitrate group) is introduced to induce intercalation. .

[Production examples and results]

<Production example of α-type cobalt hydroxide (precipitated powder)>
As an example, two sample containers containing 20 mL of an aqueous cobalt chloride solution of about 10 mM to 50 mM were used as concentration conditions. These solutions were placed in a sealed container together with about 10 mL of 2 to 10 wt .-% aqueous ammonia and allowed to stand at 25 ° C. for 3 to 12 hours. The obtained precipitate was washed and recovered by centrifugation, and dried at room temperature and atmospheric pressure.

Here, FIG. 4 shows a crystal structure of cobalt hydroxide composed of edge-sharing {CoO ₆ } octahedral clusters, (a) a crystal structure projected from the c-axis direction (a layered structure viewed from above), (B) It is the figure projected from the direction perpendicular | vertical to c-axis (viewed from the direction of the layered structure).

FIG. 5 is an electron micrograph and XRD measurement results of the obtained precipitated powder. In the figure, an electron micrograph (a, b) and an X-ray diffraction pattern (c) of the obtained α-type cobalt hydroxide crystal are shown. A hexagonal plate-like crystal having a size of about 1 to 3 μm and a thickness of about 50 to 100 nm was obtained. There were some things that were not shaped like a hexagonal plate. In the XRD pattern, the crystallinity is high, so the generally reported crystallinity is low. Unlike crystals that can only see the diffraction of (003), (006), (100), (110), many other crystals A diffraction peak derived from the surface can be observed. These peaks coincide with the α-type peak positions analyzed in detail in the previous report (Non-patent Document 8), and can be indexed as shown in the figure. In the above concentration range, there was no noticeable change in the shape and XRD pattern of the precipitated powder.

<Production example of α-type cobalt hydroxide (thin film)>
In each sample container similar to the above preparation example (precipitated powder), a substrate coated with an organic polymer matrix such as chitosan / polyaniline / polyvinyl alcohol / chitin on the slide glass and slide glass is placed on the lower side. Leaned diagonally toward This is intended to prevent the sedimentation of precipitated particles and to form a film only by heterogeneous nucleation.

6 and 7 are diagrams showing an electron micrograph and an XRD measurement result of the obtained thin film. FIG. 6 shows the obtained α-type cobalt hydroxide crystal thin film, (a, b) an electron micrograph of the thin film on the chitosan matrix, and (c, d) an electron micrograph of the thin film on the polyaniline matrix. FIG. 7 shows an X-ray diffraction pattern (a) of the obtained α-type cobalt hydroxide crystal thin film, a transmission electron microscopic image (b) of a part of the thin film, and an electron diffraction pattern (c) thereof. It can be seen that the c-axis is perpendicular to the substrate.

When a chitin / chitosan / polyaniline substrate is used, a hexagonal plate-like crystal with a size of about 1 to 3 μm and a thickness of about 50 to 100 nm sticks to the substrate, that is, the c It was oriented so that the axis was perpendicular to the substrate and deposited on the organic polymer matrix. From the XRD measurement results, the orientation was suggested by the fact that diffraction peaks only on the (003) and (006) planes were observed. In addition, a spot pattern that can be assigned to the (100) and (110) planes of α-type cobalt hydroxide was obtained from electron diffraction, which suggests that the crystallinity is high in the c-axis direction. A highly oriented film was obtained when the cobalt ion concentration was 20 mM, the ammonia concentration was 2 wt .-%, and the reaction time was 3 hours. Under other conditions, a form in which the hexagonal plate shape rises in a direction perpendicular to the substrate was observed, and the orientation was slightly disturbed. Further, when it was deposited on a polyvinyl alcohol substrate and an uncoated glass slide, hexagonal plate crystals were randomly deposited without being oriented. It is considered that the use of an organic polymer matrix for film formation, in particular, the presence of a functional group —NH— on the substrate surface, is preferable for obtaining an oriented thin film with high crystallinity. In the case of a slide glass or the like, the c-axis is not vertical but parallel, and is formed as a thin film on the substrate. Thus, there may be no orientation depending on the substrate used and the type of polymer applied thereto.

When XRD measurement results were examined in detail, it was found that (003), (006), and (00.15) when these two states were satisfied, “highly crystalline on the substrate” and “oriented”. It was found that only three peaks were observed (FIG. 7). Here, it can be expected that (003) and (006) can be observed even when the crystallinity is slightly low. However, it is considered that high-order diffraction (00.15) cannot be observed unless the above two conditions are satisfied. As a supplement, in this crystal structure, (009) does not appear as a peak due to symmetry. These correspond to the case where the number of n is different under Bragg diffraction conditions, 2d sin θ = n λ (d is constant, only the appearance of the horizontal axis θ is changed by the change of n. The structure corresponding to the d value is not formed in the crystal).

<Shape control by adding acidic organic polymer>
Add 1.5 x 10 ^-3 wt .-% of polyacrylic acid (PAA, molecular weight: 2,000), which is an acidic polymer, to each sample container similar to the preparation example (precipitated powder) and preparation example (thin film). Similar crystal growth and thin film fabrication experiments were conducted. A nanosheet precipitate having a size of about 1 μm and a thickness of about 20 to 50 nm was obtained.

FIG. 8 shows (a, b) an electron micrograph of a thin film on a chitosan matrix, (c, d) an electron microscope of a thin film on a polyaniline matrix, for an α-type cobalt hydroxide crystal thin film obtained in the presence of polyacrylic acid. It is a photograph.

FIG. 9 shows an X-ray diffraction pattern (a) of an α-type cobalt hydroxide crystal thin film obtained in the presence of polyacrylic acid, a transmission electron microscope image (b) of a part of the thin film, and an electron diffraction pattern (c) thereof. It is. In the figure, an X-ray diffraction pattern A indicates a precipitation pattern, and B indicates a thin film pattern. It can be seen that the c-axis is perpendicular to the substrate.

As shown in these figures, on the matrix (chitin / chitosan / polyaniline) where oriented thin films are obtained, these nanosheets stick to the substrate, that is, the c-axis is perpendicular to the substrate. And deposited on the organic polymer matrix. In addition, diffraction from the (100) and (110) planes was obtained as a spot pattern from the electron diffraction pattern, and a number of diffraction peaks were observed in the XRD pattern of the precipitate as when PAA was not added. This suggests that a structure with high crystallinity is maintained even when the nanosheet is formed.

<Intercalation of organic molecules during the production of α-type cobalt hydroxide>
FIG. 10 is an X-ray diffraction pattern showing the behavior of intercalation, and shows measurement results before (A) and after intercalation of thiophene-3-acetic acid (B). As an example, the same crystal growth as in the above example was performed by setting the concentration of cobalt ions to 10 mM and the concentration of organic molecules having a carboxyl group to 20 mM. A molecule in which a carboxyl group was introduced into a thiophene, imidazole, or pyridine skeleton was used for intercalation. [Chemical Formula 1] is a compound used in the intercalation during the synthesis, which is 1: glutaric acid, 2: 3-thenoyl acid (3 carboxy-thiophene), 3: thiophene-3-acetic acid, 4 : Shows the chemical structure of a compound such as imidazoleacetic acid, 5: pyridine-3-carboxylic acid. With the intercalation of these molecules, the peak position on the (003) plane indicating the layer spacing of the XRD pattern shifted as shown in [Table 1]. The compound numbers correspond to the structural formula numbers shown in [Chemical Formula 1].

[Usage]

Longer life, higher capacity, and higher output of secondary batteries are the most important issues in next-generation energy technology, and research has been conducted extensively from chemical and material manufacturers, including electrical and automobile manufacturers. . Among them, according to the technology for easily producing transition metal hydroxides that have both α-type crystal structure and high crystallinity, which has been difficult until now, and the technology related to structure control, improvement of electrochemical properties and energy storage A significant contribution to technology can be expected. In addition, according to the above-described technology, electronic materials (for example, semiconductor materials, catalysts, lithium cobalt oxide raw materials, electronics applications), magnetic materials (memory), optical materials (electrochromic elements), tires, paints, pigments, adhesives It is also conceivable to obtain precursors to cobalt oxide (CoOOH, CoO, Co ₃ O ₄ ) with agents, chemical products and other functionalities.

[Summary so far]

Transition metal hydroxides have been actively produced both academically and industrially. This embodiment realizes the selective synthesis and thinning of transition metal hydroxides that have an α-type structure, which is a metastable phase, and that have good crystallinity through a simple process near room temperature. Both industrially and industrially. In particular, the preparation and thinning of highly crystalline transition metal hydroxides having an α-type crystal structure that can be used as electrode materials and converted into various other transition metal oxides can be made into simple aqueous solutions at room temperature. It is also excellent in that it is a technology performed in the process. Hereinafter, advantages of the present embodiment will be described.

In general, it is not a thermodynamically stable crystalline phase, and a β-type structure can be obtained directly without going through the α-type, or a transition to the β-type occurs during aging during or after synthesis. Many. However, in this embodiment, an α-type structure of a metastable phase that is inherently unstable and difficult to synthesize can be selectively synthesized.

The crystal structure of the compound is a layered structure composed of layers formed by {CoO ₆ } regular octahedral clusters composed of cobalt-oxygen sharing their edges and water molecules between the layers. In many of the conventional techniques, the α-type produced is mostly irregular in its laminated structure, and it cannot be said that the crystallinity is high. However, the compound prepared by the above method has high crystallinity.

It can be deposited on a substrate in which a polymer matrix is applied to a slide glass. It was also possible to impart orientation to the precipitated crystals depending on the type of substrate used. Thinning is possible simply by immersing the base material, and it is a future application to deposit and coat crystals directly on the base material (for example, a substrate that induces non-uniform nucleation even if not a substrate). This is an important technology.

The above-described method can be realized by a solution process at room temperature and normal pressure, and can be easily realized without a special instrument or reaction apparatus. Therefore, it can be manufactured at low cost and low environmental load.

In the above-described method, the size, thickness, shape, and the like of the obtained crystal can be easily controlled. The merit of the solution process is that the shape of the precipitated particles and the thin film can be controlled by the coexisting organic molecules.

Various organic molecules can be introduced between layers (intercalation). Organic molecules coexisting at the time of synthesis can be easily introduced between layers of a layered structure by utilizing electrostatic interaction. In other words, production and functionalization of a new organic-inorganic nanocomposite using the interlayer can be expected. In addition to utilizing the α-type cobalt hydroxide crystal itself, new electrical, magnetic, and optical properties can be expected by functionalization using a wide layer.

As described above, this embodiment provides a technique for performing selective synthesis and thinning of a transition metal hydroxide having a target crystal structure with a low-cost and simple synthesis process. It is extremely important that research on life extension and high output is progressing rapidly in industry, government and academia. In particular, it is a technology that makes use of the characteristics of the solution process and can be expected to control the shape according to demand and contribute to the improvement of device characteristics.

[Cobalt oxide-related compounds and methods for producing thin films thereof]

<Overview>
The present inventors further advanced research and development, and obtained new knowledge about cobalt oxide related compounds and the like. Here, for example, cobalt oxide having a layered structure (chemical structural formula: M _x ) that can be used as a superconducting material, thermoelectric conversion material, electrode material (lithium ion secondary battery, electrochemical capacitor), magnetic material, etc. CoO ₂ · yH ₂ O; production method of alkali metal such as M = Li, Na, 0 ≦ x ≦ 1, y is arbitrary, Co valence is 3 or more and 4 or less. By going through the above-described method for producing α-type cobalt hydroxide, it is possible to realize a method for producing a cobalt oxide-related compound using an aqueous solution in which all steps are performed at room temperature and near atmospheric pressure. More specifically, the production of sodium cobaltate, which is a superconducting material and thermoelectric conversion material, and lithium cobaltate, which is an electrode material, can also be realized by a simple method under mild conditions by chemical oxidation in an aqueous solution process. It becomes.

<Background>
In recent years, with increasing interest in environmental issues on a global scale, development of processes that do not place a burden on the environment is also required in material synthesis. In particular, in the production of ceramics, a process that requires high temperature and pressure control is the center, and establishment of a synthesis method with lower cost and lower environmental load is required. It has been difficult to develop a process for synthesizing various functional inorganic materials in an aqueous solution, as living organisms produce inorganic components such as bones and teeth in a mild environment.
Among transition metal compounds, compounds with a layered structure composed of cobalt-oxygen octahedral clusters control superconducting materials, thermoelectric conversion materials, electrode materials, magnetism by controlling the distance between layers or ionic species. There is a wide range of applications to materials. However, these compounds have been synthesized by using cobalt compounds and alkalis as raw materials and undergoing high-temperature sintering processes and electrochemical techniques, but they require a multi-step and long-time process. . A simple, low-cost, low environmental load synthetic route has not been developed. In addition, a process that undergoes sintering at a high temperature is difficult to say as a synthesis method with controllability in order to improve characteristics and to put it to practical use as a device. Specifically, there are some disadvantages such as disappearance of the nanoscale structure formed by sintering, restrictions on the base material necessary for forming a thin film, and burning of organic substances in the organic-inorganic composite.

The compound itself represented by Na _x CoO ₂ and its production process through high-temperature firing have already been published in the following literature by several research groups. Note that Non-Patent Document 9 is the first report regarding the development of superconducting properties in materials other than copper and cobalt.

JP 2004-262675 Hydrohydrate sodium cobalt oxide JP-A-2005-350331 Sodium hydrated sodium cobalt oxide and method for producing the same JP-A-2006-222397 Heat transfer conversion layered cobalt oxide and synthesis method thereof Patent application title: Lithium Cobaltate, Method for Producing the Same, and Lithium Ion Battery Using the Same Method for producing layered rock salt type lithium cobalt oxide by hydrothermal oxidation method

<Specific contents>
<< Production Method of Cobalt Oxide Related Compounds >>
Hereinafter, a cobalt oxide related compound is obtained by chemically oxidizing in an aqueous solution using α-type cobalt hydroxide (α-Co (OH) ₂ ) crystal having a layered structure produced by the above-mentioned method as a precursor. Obtained.
As an example, each of the powder sample and the thin film sample was treated (a) immersed in a sodium hypochlorite (NaClO) aqueous solution (b) immersed in a NaClO aqueous solution + NaOH (c) three treatments of immersion in a NaClO aqueous solution + LiOH at room temperature A sample of cobalt oxide was produced under conditions of near normal pressure. The chemical structures of the compounds produced by the three treatment methods were different. However, there was no difference in structure between the powder sample (precipitate) and the thin film sample under the same processing conditions.

The experimental conditions are shown for each of the processing conditions (a) to (c).

{About (Processing A)}
Cobalt oxide was obtained by immersing the precipitated α-type cobalt hydroxide (α-Co (OH) ₂ ) crystal powder and thin film in a commercially available NaClO aqueous solution.

The concentration of sodium hypochlorite is preferably 0.5 wt .-% or more for both the powder sample and the thin film sample, and more preferably within the range of 0.5 wt .-% to 5.0 wt .-%. This is because the oxidation reaction does not proceed completely at less than 0.5 wt .-%. 5.0 wt .-% or less is preferable because of the highest concentration of commercially available NaClO aqueous solution, but it is considered that there is no change in the result even if the value is larger than this.

If the reaction time is 5 seconds or longer in the powder sample, the influence of the length of the reaction time does not appear even when the reaction time reaches 48 hours. However, it is preferable to uniformly disperse the powder in the solution by stirring or ultrasonic treatment. In a thin film sample, it is preferably 1 second or longer and 60 seconds or shorter, more preferably 5 seconds or longer and 10 seconds or shorter. This is because if the reaction time is short for 5 seconds, the oxidation reaction does not proceed completely, and unreacted substances may remain. Further, if the reaction time is longer than 10 seconds, it may be peeled off from the substrate.

{About (Processing A and C)}
This is a cobalt oxide (chemical structural formula; M _x CoO ₂ · yH ₂ O; M = alkali metal such as Li, Na, 0 <x <1, y is optional, Co valence is 3 or more and 4 or less) It is a manufacturing method. When introducing Na ions or Li ions into the layered structure, NaOH or LiOH is added to the NaClO aqueous solution.

The sodium hypochlorite concentration is preferably in the range of 0.05 .-% to 0.5 wt .-%. This is because the oxidation reaction does not proceed moderately at less than 0.05 wt .-%. This is because, when the concentration is higher than 0.5 wt .-%, it is difficult to selectively introduce the added alkali ions into the layer.

The concentration of alkali ions is preferably from 0.1 mol / L to 5 mol / L. This is because the rate of the oxidation reaction does not decrease at less than 0.1 mol / L. This is because α-Co (OH) ₂ crystals are transferred to other crystal forms or crystals such as CoOOH at concentrations higher than 5 mol / L.

The reaction time is preferably 1 hour or longer together with the powder sample and the thin film sample. This is because if the reaction time is short, the oxidation reaction and the introduction of alkali ions into the layer do not proceed moderately. A long reaction time does not affect the reaction, but in the case of a thin film sample, it may be peeled off from the substrate.

《Considerations for production compounds》
Examples will be described in the order of powder sample and thin film sample.

{Powder sample}
FIG. 11 is a scanning electron micrograph of the obtained cobalt oxide plate crystal (powder sample) (a) treatment with a NaClO solution (after drying), b) treatment with a NaClO solution and LiOH). Regarding the powder sample, the α-type cobalt hydroxide (α-Co (OH) ₂ ) crystal that was not oxidized was a plate-like crystal with a size of 1 μm to 5 μm and a thickness of about 50 nm. . Even after any of the above treatments (a) to (c), as shown in the figure, the macro plate-like form was not changed from that before the oxidation reaction.

FIG. 12 is a transmission electron micrograph showing the nanostructure of the obtained cobalt oxide plate crystal (powder sample). As shown in the figure, at the nanometer level, with the formation of cobalt oxide, the 2-3 nm nanocrystals changed to a structure with the same crystal orientation. This is considered to be a structure produced because the volume of the two is different when the structure conversion from cobalt hydroxide to cobalt oxide occurs. Such a nanoscale structure is difficult to produce by a conventional firing method, which is a unique point of this method. This space formed between the nanocrystals can be used as a flow path for diffusing electrolytes and substances, and can be said to be a structure suitable for exchange of substances with the outside.

Figure 13 shows X-ray diffraction patterns of cobalt oxide plate crystals (powder sample) by various treatments (a) treatment with NaClO solution (before drying), b) treatment with NaClO solution (after drying), c) NaClO solution Treatment with NaOH, d) treatment with NaClO solution and LiOH). Here, the layered structure and its layer spacing were analyzed by X-ray diffraction measurement (XRD). By NaClO treatment (a), the peak of the layer spacing on the low-angle side showing a layered structure is from about 0.8 nm to about 9.2 nm to 9.8 nm before drying the sample, and from about 7.2 nm to 7.6 nm after drying. changed. The change in the layer interval before and after the drying of the sample was caused by the deinsertion of water molecules hydrated between the layers, and reversibly changed in response to repeated addition of water to the sample and drying. Corresponding to the fact that divalent cobalt ions were oxidized to tri to tetravalent, the (100) plane spacing in the layer was changed from about 0.27 nm to about 0.24 nm, and the (110) plane spacing was about 0.16 nm. Shifted from about 0.14 nm to about 0.14 nm (this value does not depend on the dry state of the sample). The structure at this time can be estimated as Na _x CoO ₂ · yH ₂ O (0.2 <X <0.3, 0.6 <y <1.2) in a dry state. In the treatment with NaClO and NaOH (a) and the treatment with NaClO and LiOH (c), the layer spacing indicating the layered structure changed from about 0.8 nm to about 0.64 nm to 0.68 nm. In the treatment (a) and the treatment (c), no change in the layer interval due to the dry state was observed. Similarly to the treatment (a), corresponding to the fact that the divalent cobalt ion was oxidized to 3 to 4 valence, the (100) plane spacing in the layer was changed from about 0.27 nm to about 0.24 nm. The surface spacing of the (110) plane shifted from about 0.16 nm to about 0.14 nm. The structures at this time are Na _x CoO ₂ · yH ₂ O (0.2 <X <0.4, 0.3 <y <0.9) in the treatment (b) and Li _x CoO ₂ · yH ₂ O (0.2 <in the treatment (c), respectively. X <0.4, 0.3 <y <0.9)

{Thin film sample}
For thin-film samples, α-type cobalt hydroxide (α-Co (OH) ₂ ) crystals that have not been oxidized are such that plate crystals with a size of 1-5 μm and a thickness of about 50 nm follow the substrate. The c-axis of the crystal was oriented in the direction perpendicular to the substrate.

FIG. 14 is a scanning electron micrograph of the obtained cobalt oxide plate crystal (thin film sample) (a) a cobalt oxide nanosheet oriented thin film, and b) a cobalt oxide plate crystal oriented thin film). Even after the oxidation treatments (a) to (c), the morphology and orientation of these thin film crystals were maintained.

Fig. 15 shows X-ray diffraction patterns of cobalt oxide plate crystals (thin film samples) by various treatments (a) treatment with NaClO solution (after drying), b) treatment with NaClO solution and NaOH, c) treatment with NaClO solution and LiOH. Processing). The layer spacing of the layered structure changed in the same manner as the powder sample with the oxidation treatments (a) to (c). Similarly, the spacing between the (100) plane and the (110) plane within the layer is also shifted from 0.27 nm to about 0.24 nm, and the (110) plane spacing is shifted from about 0.16 nm to about 0.14 nm. This was confirmed by electron beam diffraction. From the above, it is considered that the same cobalt oxide as in the powder sample was produced in the thin film sample.

<Summary of cobalt oxide related compounds>
The above-mentioned method is a simple process that can synthesize cobalt oxide-related compounds in an aqueous solution process near room temperature and normal pressure without sintering. It is excellent in that a cobalt oxide oriented thin film maintaining a cobalt oxide oriented thin film can be obtained, that it is a cobalt oxide crystal composed of nanocrystals, and that size, thickness, shape, and the like can be controlled.

According to the above-described method, for example, a cobalt oxide having a layered structure (chemical structural formula: M _x CoO ₂ · yH ₂ O; an alkali metal such as M = Li, Na, 0 <x <1, y is arbitrary, Co valence of 3 or more and 4 or less) can be synthesized from the cobalt salt and alkali as starting materials by an aqueous solution process under normal conditions and mild conditions around 25 ° C. This method is an aqueous solution process under mild conditions that does not require sintering, and is excellent in that the reaction time is short, nanoscale structure control, thin film formation, and crystal orientation control can be easily performed. ing.
As described above, it has become possible to synthesize sodium cobaltate and lithium cobaltate, which have been manufactured through a high-temperature sintering process, in an aqueous solution process in a low-cost and low-environmental environment. In addition, as a feature of the aqueous solution process, it was possible to easily control the structure. According to the above-described method, since it is not necessary to sinter, it is possible to maintain a nano-scale structure, and thus it is possible to expect the development of new characteristics and improvement of physical properties. The space formed between the nanocrystals can be used as a flow path for diffusing electrolytes and substances, and can be said to be a structure suitable for exchange of substances with outside.

Sodium cobaltate is attracting attention as an inexpensive superconducting material and thermoelectric conversion material, and lithium cobaltate as a material for lithium ion secondary battery electrodes regardless of industry, government or academia. These compounds also utilize catalysts, petroleum catalysts, oxidants, glass materials, colorants, pigments, pottery, livestock nutrients, other salt materials, ceramic coloring, ferrite, and excellent absorption characteristics of incident light It may be used as a heat conversion material for light, a display application utilizing an electrochromy characteristic or a taking in / out characteristic such as Li ion, and an electronic material. You may grind | pulverize the above-mentioned compound with grinders, such as a sample mill, as needed.

In particular, since lithium cobaltate can control even a crystal structure according to the above-described method, there is a possibility that a positive electrode for a lithium battery having a desired energy density can be obtained. If the energy density of the positive electrode for a lithium battery can be improved, the above-described method is very significant in that the possibility of use is greatly increased even if it is a rare material. When lithium cobaltate is used as the positive electrode for lithium batteries, the positive electrode is manufactured by dissolving an active material such as lithium cobaltate on both sides of the aluminum foil with a solvent, drying and pressing to increase the density. May be.

For example, when used for a coin-type battery, a carbon-based conductive agent such as acetylene black, carbon or graphite powder, or a binder such as polytetrafluoroethylene resin or polyvinylidene fluoride is added to the above-described lithium cobalt oxide. It can be obtained by kneading and pellet molding. In addition, when used for a cylindrical or rectangular battery, an organic solvent such as N-methylpyrrolidone is added to the above lithium cobaltate in addition to these additives, kneaded to form a paste, and a metal such as an aluminum foil. It can be obtained by coating on a current collector and drying.

Lithium battery electrolyte contains electrochemically stable lithium ions dissolved in a polar organic solvent that does not oxidize or reduce in a wider range than the potential range of operation as a lithium ion battery. Can be used. As the polar organic solvent, for example, propylene carbonate, ethylene carbonate, diethyl carbonate, dimethoxyethane, diethoxyethane, tetrahydrofuran, γ-butyllactone, or a mixture thereof can be used. Lithium perchlorate, lithium hexafluorophosphate, lithium tetrafluoroborate, or the like can be used as a solute serving as a lithium ion source. A porous polypropylene film or polyethylene film is disposed between the electrodes as a separator. Battery types include a separator placed between a pellet-shaped positive electrode and negative electrode, crimped onto a sealing can with a polypropylene gasket, injected with an electrolyte, and sealed coin type, positive electrode material or negative electrode Examples include a cylindrical type in which a material is applied on a metal current collector, wound around a separator, inserted into a battery can with a gasket, an electrolyte is injected, and sealed. There is also a tripolar battery intended to measure electrochemical properties. In this battery, a reference electrode is also arranged in addition to the positive electrode and the negative electrode, and the electrochemical characteristics of each electrode are evaluated by controlling the potential of the other electrode with respect to the reference electrode.

Thus, the above-described technology is likely to become an extremely important technology for the next generation industry as a material synthesis process with low cost and low environmental load.

<Others>
Examples of the alkali ion source include sodium hydroxide and potassium hydroxide (which may be either an anhydride or a hydrate), and these may be used in combination. In particular, chlorides, nitrates, sulfates, hydroxides and the like are used, and more specifically, lithium hydroxide (which may be either an anhydride or a hydrate), lithium chloride, and the like. May use 2 or more types together.

Cobalt oxide compounds have been mainly described. Nickel oxide compounds in which Co is replaced with Ni (chemical structural formula: M _x NiO ₂ · yH ₂ O; alkali metals such as M = Li, Na, 0 <x <1, It has been found that y is arbitrary, and the valence of Ni is 3 or more and 4 or less). The same applies to a multi-component compound containing both Co and Ni.

[Interpretation of rights, etc.]

The present invention has been described above with reference to specific embodiments. However, it is obvious that those skilled in the art can make modifications or substitutions of the embodiments without departing from the gist of the present invention. That is, the present invention has been disclosed in the form of exemplification, and the contents described in the present specification should not be interpreted in a limited manner. In order to determine the gist of the present invention, the claims section described at the beginning should be considered.

It will also be appreciated that illustrative embodiments of the invention achieve the above objects, but that many modifications and other examples can be made by those skilled in the art. The elements or components of each embodiment described in the claims, specification, drawings, and description may be employed in combination with one or more other elements. The claims are intended to cover such modifications and other embodiments, which are within the spirit and scope of the present invention.

For example, a technique for easily producing a transition metal hydroxide having both an α-type crystal structure and high crystallinity and a technique related to structure control can be expected to greatly contribute to improvement of electrochemical characteristics and energy storage technology. In addition, according to the above-described technology, for example, electronic materials (for example, semiconductor materials, catalysts, raw materials for lithium cobaltate, electronics applications), magnetic materials (memory), optical materials (electrochromic elements), tires, paints, pigments It is also possible to obtain precursors to cobalt oxide (CoOOH, CoO, Co ₃ O ₄ ) having adhesives, chemical products, and other functions.

Claims (33)

1. A transition metal hydroxide film formed on a substrate,
   A transition metal hydroxide film, wherein a crystal axis of the transition metal hydroxide film is oriented with respect to the surface of the substrate.
2. 2. The transition metal hydroxide film according to claim 1, wherein the transition metal is any one of Zn, Cu, Ni, Mn, and Co.
3. An α-type cobalt hydroxide film formed on a substrate,
   An α-type cobalt hydroxide film, wherein the c-axis of α-type cobalt hydroxide is oriented with respect to the surface of the substrate.
4. 4. The α-type cobalt hydroxide film according to claim 3, wherein a molecule different from α-type cobalt hydroxide is introduced between layers of α-type cobalt hydroxide.
5. An α-type cobalt hydroxide film formed on a substrate,
   An α-type cobalt hydroxide film, wherein diffraction peaks derived from the (003) plane, the (006) plane, and the (00.15) plane are observed in X-ray diffraction.
6. Solid transition by hydroxylating the transition metal while increasing the pH of the solution while coordinating a substance having a functional group that coordinates with the transition metal, which is different from the hydroxy group, with the transition metal in the solution A method for producing a solid transition metal hydroxide, comprising forming a metal hydroxide.
7. 7. The method for producing a solid transition metal hydroxide according to claim 6, wherein the transition metal is any one of Zn, Cu, Ni, Mn, and Co.
8. 7. The method for producing a solid transition metal hydroxide according to claim 6, wherein the substance having a functional group coordinated with the transition metal is a volatile base.
9. 7. The method for producing a solid transition metal hydroxide according to claim 6, wherein the substance having a functional group coordinated with the transition metal is ammonia.
10. 7. The transition metal solution according to claim 6, wherein a molecule that intercalates between layers of a solid transition metal hydroxide is added, and the molecules are intercalated between layers of a solid transition metal hydroxide. Solid transition metal hydroxide production method.
11. A method for producing α-type cobalt hydroxide, comprising forming α-type cobalt hydroxide while increasing pH by dissolving a volatile base gas in a cobalt ion solution.
12. 12. The method for producing α-type cobalt hydroxide according to claim 11, wherein a molecule having a functional group coordinated with cobalt ions is added to the cobalt ion solution.
13. 12. The method for producing α-type cobalt hydroxide according to claim 11, wherein the substrate is immersed in the cobalt ion solution to form α-type cobalt hydroxide on the substrate.
14. 12. The method for producing α-type cobalt hydroxide according to claim 11, wherein a functional group that coordinates with cobalt ions is present on the surface of the substrate.
15. 12. The α type according to claim 11, wherein a molecule that intercalates between layers of α-type cobalt hydroxide is added to the cobalt ion solution, and the molecules are intercalated between layers of α-type cobalt hydroxide. Cobalt hydroxide manufacturing method.
16. A solid transition metal hydroxide production method comprising forming a solid transition metal hydroxide by gradually dissolving a volatile base gas into a transition metal solution.
17. Storing the first container containing the transition metal solution and the second container containing the volatile base solution together in the third container;
    Solid transition having a step of increasing the pH of the solution in the first container by diffusing the volatile base gas volatilized from the second container into the third container and dissolving in the solution in the first container Metal hydroxide manufacturing method.
18. Storing both the first container containing the cobalt ion solution and the second container containing the ammonia solution in the third container;
    A step of increasing the pH of the solution in the first container by diffusing ammonia gas volatilized from the second container into the third container and dissolving in the solution in the first container. Cobalt oxide production method.
19. A gas container containing polyacrylic acid and cobalt ion solution to be intercalated, and the first container in which the substrate is immersed and the second container in which the ammonia solution is contained are housed in a sealed container, and the ammonia gas volatilized from the ammonia solution. Diffusing in a sealed container;
    And increasing the pH of the cobalt ion solution by dissolving the ammonia gas in the cobalt ion solution,
    A method for producing α-type cobalt hydroxide, characterized in that α-type cobalt hydroxide in which the molecules intercalate between layers of α-type cobalt hydroxide is formed on a substrate.
20. Means for holding a transition metal solution;
    Means for dissolving volatile base gas in the transition metal solution,
    An apparatus for producing a solid transition metal hydroxide, wherein the volatile base gas dissolves in the transition metal solution to form a solid transition metal hydroxide while increasing the pH.
21. Having a step of reacting a transition metal hydroxide with hypochlorite ion,
    The method for producing a transition metal oxide, wherein the transition metal is any one of Ni and Co.
22. 22. The method for producing a transition metal oxide according to claim 21, wherein the transition metal hydroxide is reacted with hypochlorite ions in the presence of an alkali ion source.
23. 22. The method for producing a transition metal oxide according to claim 21, wherein the transition metal is Co.
24. 24. The method for producing a transition metal oxide according to claim 23, wherein the transition metal hydroxide is α-type cobalt hydroxide.
25. 24. The method for producing a transition metal oxide according to claim 23, wherein the transition metal hydroxide is α-type cobalt hydroxide crystal.
26. A step of reacting a transition metal hydroxide film formed on a substrate and having a crystallographic axis of the transition metal hydroxide film oriented with respect to the surface of the substrate with hypochlorite ions;
    The method for producing a transition metal oxide film, wherein the transition metal is any one of Ni and Co.
27. Forming a transition metal hydroxide by dissolving volatile base gas in the transition metal solution;
    Reacting the transition metal hydroxide with hypochlorite ions,
    The method for producing a transition metal oxide, wherein the transition metal is any one of Ni and Co.
28. The first container containing the polyacrylic acid and cobalt ion solution and the substrate immersed therein and the second container containing the ammonia solution are both housed in a sealed container, and the ammonia gas volatilized from the ammonia solution is diffused into the sealed container. A process of
    Increasing the pH of the cobalt ion solution by dissolving the ammonia gas in the cobalt ion solution, and forming α-type cobalt hydroxide on the substrate;
    Immersing the α-type cobalt hydroxide in a solution in which lithium ions and hypochlorite ions are dissolved.
29. A transition metal oxide film formed on a substrate,
    A transition metal oxide film, wherein the crystal axis of the transition metal hydroxide film is oriented with respect to the surface of the substrate.
30. 30. The transition metal oxide film according to claim 29, wherein the transition metal is one of Ni and Co.
31. A cobalt oxide film formed on a substrate,
    A cobalt oxide film, wherein the c-axis of the cobalt oxide film is oriented with respect to the surface of the substrate.
32. 32. The cobalt oxide film according to claim 31, wherein an alkali metal is introduced between the cobalt oxide layers.
33. The solid transition metal hydroxide production method or α-type cobalt hydroxide production method according to any one of claims 6 to 19, or the transition metal oxidation according to any one of claims 21 to 28. An electronic material manufactured by a method for manufacturing a product or a method for manufacturing a hydrated lithium cobalt oxide.

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