JPH02221106A - Production of metal oxide based ionic conductor - Google Patents

Abstract

PURPOSE:To synthesize a good quality metal oxide by a liq. phase reaction, to dope the oxide with a guest material in the reaction process and to obtain the metal oxide based ionic conductor having a uniform composition and a large diffusion coefficient of the guest ion by hydrolyzing a metal alkoxide, etc., in the soln. in the presence of a metallic salt. CONSTITUTION:(A) At least one kind among a metal alkoxide (e.g. titanium tetraisopropoxide), a metal beta-diketon type org. material (e.g. acetylacetonatotitanium-oxide (II)) or a mixture of a metal alkoxide and a metal beta-diketone (e.g. titanium bis-acetylacetonate bis-isopropoxide) and (B) at least one kind among alkali metallic salts (e.g. lithium iodide) and metal halides (e.g. titanium tetrachloride) are made coexistent in a solvent (one atom of the A metal is mixed with 1.6-2.0 atoms of the B metal, and the concn. of A is controlled to 0.5-2.0mol/dm<3>). The soln. is hydrolyzed at 30-70 deg.C, and the formed ionic conductor is washed with water, dried and then calcined at 380-490 deg.C for 7-9hr.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for producing a metal oxide-based ionic conductor for use in electrochemical devices such as batteries, sensors, electrochromic devices, and potential storage devices.

[Prior Art] Conventionally, metal oxide-based ionic conductors are generally obtained by using a metal oxide as a host material and doping it with a guest material such as an alkali metal ion chemically or electrochemically. .

The general method for synthesizing metal oxides, which are host substances, is to sinter and thermally decompose metal nitrates, carbonates, or metal elemental oxide powders in the atmosphere to produce sintered oxides. It has been adopted.

On the other hand, as a method of electrochemically doping a host material with a guest material, a method of electrochemically oxidizing or reducing the host material in a solvent in which the guest material is dissolved is very commonly adopted. In addition, as a method of chemically doping a host material with an alkali cation as a guest material, M. Niss Whitingham (
Journal of the Electrochemical ψ Society (J, EI
eCtrOCheIlsoc, Vol. 124, No. 9, pp. 1387-1988 (1977)], a method of impregnating a guest substance using a hexane solution of n-butyllithium,
[InorgChew, D.W. Hurphy et al.
), Vol. 18, No. 10, p. 2800 (1979), in which a solution of lithium iodide in acetonitrile is used to directly react with a host material, etc., have been adopted.

[Problems to be Solved by the Invention] However, the conventional method for producing the metal oxide host material has the following problems:
Since it is essentially a solid-solid phase reaction, it is difficult to obtain a homogeneous material, which has the drawback of easily causing poor ionic conductivity. Therefore, a method for producing a highly homogeneous metal oxide host material is awaited. Furthermore, the electrochemical doping method for guest substances has the problem that operations such as setting the current density to control ion migration are too complicated and are not suitable for industrialization. Although this is a conventional doping method, it is difficult to obtain an ionic conductor with a uniform composition, and therefore the apparent diffusion coefficient of the guest substance in the produced ionic conductor becomes small, that is, the ionic conductivity is not good.

The present invention was made to solve the above-mentioned problems, and it synthesizes high-quality metal oxides by liquid phase reaction, and at the same time, dopes a guest substance during the reaction process to achieve a uniform composition. The purpose is to scale metal oxide-based ionic conductors that have a large diffusion coefficient for guest ions.

[Means for Solving the Problems] The present invention provides at least one of a metal alkoxide, a metal β-diketone type organic substance, and a mixture of a metal alkoxide and a metal β-diketone type organic substance, an alkali metal salt, and a metal halide. After making at least one of the metal alkoxide and metal β-
Diketone type organic substances, metal alkoxides and metal β −
The present invention relates to a method for producing a metal oxide-based ionic conductor, which comprises a step of hydrolyzing at least one of the mixtures with a diketone-type organic substance.

[Example] The metal alkoxide, the metal β-diketone type organic substance, and the mixture of the metal alkoxide and the metal β-diketone type organic substance used in the present invention are the starting materials of the host material.

There is no limitation to the metal alkoxide, but the host material gold W! ! In order for the b oxide to have a layered structure or a tunnel-like structure, it must be in group ■a, group Va, or ■a in the periodic table of elements.
At least one alkoxide of a transition metal such as a transition metal belonging to the group A, a transition metal such as Hn, or a metal such as M or Zn is preferable. The alkoxyl group forming this metal alkoxide may have any number of carbon atoms, and may be an alkoxyl group derived from a polyhydric alcohol.

Preferred specific examples of such alkoxyl groups include:
For example, methoxyl group, ethoxyl group, n-propoxyl group, i-propoxyl group, n-butoxyl group, 5ec
-butoxyl group, °C-butoxyl group, etc.

If multiple alkoxyl groups are bonded to the metal,
The plurality of alfxyl groups do not need to be of the same type. Further, it may be a metal alkoxide having a plurality of metal atoms, and in that case, the plurality of metal atoms need not be of the same type.

For example, the structure of metal alkoxide is - general formula (■
): (In the formula, Hl is a metal atom, and RI R2R3R4 are all alkyl groups.)
It may also be a compound with a dinuclear structure as shown by °l (l l (2R3R4 is the same as above, R2 is a metal atom, and R5R8 is an alkyl group).Of course, the metal alkoxide used in the present invention can be a metal alkoxide. The coordination number is the general formula (1
) and (not limited to 4 as represented by t).

Preferred specific examples of such metal alkoxides include titanium tetraisopropoxide, titanium tetraethoxide, titanium tetrabutoxide, zirconium tetraethoxide, zirconium tetrapropoxide,
Examples include aluminum triethoxide and aluminum triisobutoxide.

The metal β-diketone type organic substance is a compound having a structure in which a β-diketone type ligand is coordinated to a central metal, and is not particularly limited.

Typical examples thereof include compounds represented by the general 2G[l:Ha (in the formula, H3 is a metal atom, R7RI R9R10 is an alkyl group or an aryl group); for example, (CHsC0CHCO
It may also be a compound in which a portion is an oxide, such as CHs )28OOa. As the metal atom, at least one of the transition metals is used, as in the case of metal alkoxides.
Seeds are preferred. Further, the plurality of alkyl groups and aryl groups contained in the metal β-diketone type organic substance do not need to be of the same type. Preferred specific examples of such alkyl groups and aryl groups include methyl group, ethyl group, rhopropyl group, i-propyl group, n-butyl group, 5ec-butyl group, t-butyl group, amyl group, and phenyl group. group, tolyl group, xylyl group, etc. Of course, the metal β-diketone type organic substance used in the present invention is not limited to those having a metal coordination number of 4 as represented by the general formula circle.

Specific examples of metal β-diketone type organic substances include titanium oxide (1) acetylacetonate, aluminum acetylacetonate, manganese [1) acetylacetonate, anganese acetylacetonate, zirconium acetylacetonate, etc. .

The mixture of metal alkoxide and metal β-diketone is, for example, represented by the general formula: RI3\R' (wherein H4 is a metal atom, RnB12 is an alkyl group, and 1'3BH is an alkyl group or an aryl group). Structure as a metal alkoxide and metal β as shown in
-It is a compound that has the structure of a diketone type organic substance.

Specific examples of the mixture include titanium bisacetylacetonate bisisopropoxide.

Further, as the acid used in this synthesis method, any mineral acid (inorganic acid) or organic acid can be used.

The alkali metal salt and metal halide are substances for supplying alkali metal ions and halogen anions as guest ions.

Examples of the alkali metal salt include Ll and Ha.

Examples include alkali metal halides, carbonates, hydroxides, 111-acid salts, perchlorates, sulfates, iodates, organic acid salts, etc.

Specific examples of these alkali metal salts include lithium chloride, lithium iodide, lithium carbonate, lithium bromide, lithium hydroxide, lithium nitrate, lithium perchlorate, sodium fluoride, sodium chloride, sodium bromide, and iodine. sodium chloride, sodium carbonate, sodium hydrogen carbonate, sodium hydroxide, sodium nitrate, sodium perchlorate, potassium fluoride, potassium chloride, potassium bromide, potassium iodide, potassium carbonate, potassium hydrogen carbonate, potassium hydroxide, potassium nitrate, Examples include potassium perchlorate.

The metal halide is preferably a transition metal halide (F, CI, Br, etc.).

Specific examples of metal halides include titanium tetrachloride, zirconium tetrachloride, manganese bromide, manganese chloride, aluminum fluoride, aluminum chloride, aluminum bromide, aluminum iodide, zinc fluoride, zinc chloride, and zinc bromide. , zinc iodide, etc.

In the method of the present invention, first, at least one of a metal alkoxide, a metal β-diketone type organic substance, and a mixture of a metal alkoxide and a metal β-diketone type organic substance (hereinafter also referred to as a metal alkoxide, etc.), and an alkali metal salt. and at least one metal halide (hereinafter also referred to as alkali metal salt or the like) are allowed to coexist in the solvent.

The solvent is not particularly limited, and examples include inorganic solvents such as carbon tetrachloride and carbon disulfide, and organic solvents such as ethanol, isopropanol, benzene, thiophene, pyridine, diethyl ether, acetonitrile, and dimethyl sulfoxide. It will be done. These solvents are
They may be used alone or in combination of two or more.

In the layer using an alkali metal salt, etc., the metal atom contained in the alkali metal salt etc. is preferably 0.1 to 2.8 atoms per 1 metal atom contained in the metal alkoxide etc., and 1.6
~2.0 atoms are particularly preferred. If the amount used is less than 0.1 atom, the ionic conductivity tends to be impaired because a sufficient amount of tunnels for alkali ions to move cannot be created in the crystal structure of the ionic conductor.
If the number exceeds 8 atoms, the crystal structure of the ionic conductor is disturbed, and the ionic conductivity tends to be impaired.

There is no particular limitation on the amount of solvent used, but the concentration of metal flukoxide etc. is usually 0.5 to 2. Oa+.

The yield is highest when di'.

When the metal alkoxide, etc. and the alkali metal salt, etc. are made to coexist in the solvent, there is no particular limitation on the order of addition and mixing; for example, the alkali metal salt, etc. may be added after mixing the metal alkoxide, etc. with the solvent. Often, an alkali metal salt or the like may be added to the solvent and then a metal alkoxide or the like may be mixed therein. Note that the metal alkoxide, etc., alkali metal salt, etc. may be dissolved, dispersed, suspended, etc. in the solvent, or may be partially precipitated, and then the metal alkoxide, etc. in the solvent is hydrolyzed.

There are no particular limitations on the method of adding water during hydrolysis, the conditions during hydrolysis, etc., but the amount of water added during hydrolysis is preferably in large excess relative to the metal alkoxide, etc. Preferably, the temperature is 30-70°C. As the water to be added, ion-exchanged water, distilled water, etc. that do not contain metal ions are used.

Through such hydrolysis, metal alkoxides and the like are hydrolyzed while incorporating at least one of alkali cations and halogen anions, and the host material has good ionic conductivity and the metal oxide ions are uniformly doped with guest ions. Electrical conductors are produced in a single reaction.

The obtained ionic conductor is dried, washed with water, etc., then molded and used in electrochemical devices.

The hydrolyzed product is preferably used after being fired, since it becomes an oxide that provides a stable path for ions, which are conductive species, and increases the ion diffusion coefficient.

The above-mentioned calcination is usually performed after drying the hydrolyzed product, washing with water, etc., and the calcination temperature is preferably 300°C or higher to completely remove water contained in the unfired product, and the crystal structure In order to avoid transformation, the temperature is preferably 500°C or lower, and more preferably 380 to 490°C. In addition, the firing time was set at 3.
~10 hours is preferred, and 7 to 9 hours is more preferred.

The resulting fired product is dried, washed with water, and then shaped.
Used in electrochemical devices.

As explained above, the synthesis reaction in the production method of the present invention is essentially different from conventional synthesis and ion-doping processes, and includes: - Since it is based on a gel method and uses metal alkoxides as starting materials, the product metal oxide-based ionic conductor can be obtained as fine particles with uniform particle sizes, which allows it to move back and forth between the ionic conductor and the solvent. The area of the interface, which is the site of the reaction, increases dramatically compared to conventional ones, increasing the apparent diffusion coefficient of ions. Because of doping, it is estimated that the composition is uniformly doped with ions at the molecular level (which cannot be obtained by any conventional synthesis method), and by increasing the ion diffusion coefficient,
It is thought that a metal oxide-based ionic conductor having a larger apparent diffusion coefficient can be obtained compared to metal oxide-based ionic conductors obtained by conventional methods.

The metal oxide-based ionic conductor produced by the method of the present invention can be used, for example, in electrochemical devices such as batteries, sensors, electrochromic devices, and potential storage devices.

Next, the method of the present invention will be explained in more detail using Examples, but the present invention is not limited thereto.

Example 1 Titanium tetraisopropoxide 15.76Q was used as a metal alkoxide, and isopropyl alcohol 1 was used as a solvent.
It was dissolved in 00α3. In this solution, 7.421 g of lithium iodide was dissolved as an alkali metal halide, and then 5 m of water was added at 25° C. for hydrolysis to obtain a sol-like reaction product. The obtained reaction product was filtered and then dried under reduced pressure. After washing this with warm water at 60℃,
It was dried again under reduced pressure to obtain a metal oxide-based ionic conductor according to the present invention. The obtained ion conductor was amorphous, and its composition was examined by ICP (plasma emission spectrometry) and found to be Li, 8Tith. When the obtained ionic conductor was observed under an electron microscope, it was found to be fine particles with uniform particle sizes.

Furthermore, in order to clarify the effect of firing, this was fired at 450 to 500°C for 8 hours in the open atmosphere, and the composition was
An ionic conductor of i0.8T+02 (confirmed by compositional analysis) was obtained.

The resulting unfired and fired products each cost 260k.
The working electrode was formed into a pellet at a pressure of g/cd-G, and lithium foil was used as the counter electrode and reference electrode, Li CJ.
A measurement cell was assembled using a 1H propylene carbonate solution of No. 04 as an electrolyte. Using this cell, the apparent diffusion coefficient of lithium ions was measured by the current pulse method. The results are shown in Table 1.

Example 2 Titanium oxide [111
Acetylacetonate 13.110 was mixed with absolute ethanol 100α3 as a solvent. In this solution, 2.129 g of lithium chloride was dissolved as an alkali metal halide, and then 10 Id of water was added at 25° C. for hydrolysis to obtain a sol-like reaction product. The obtained reaction product was filtered, washed with ethanol, and then dried under reduced pressure to obtain a metal oxide-based ionic conductor according to the present invention. The selected ionic conductor is amorphous, and its composition is Lio.
, 7Ti02. The obtained ionic conductor is SEN
@As it turned out, they were fine particles with uniform particle sizes.

Furthermore, in order to clarify the effect of firing, this was fired at 450 to 500°C for 8 hours in the open atmosphere, and the composition was
i, TiO2 (confirmed by compositional analysis) ionic conductor was obtained.

Then, the apparent diffusion coefficient of lithium ions was measured in the same manner as in Example 1. The results are shown in Table 1.

Comparative Example 1 A hexane solution of n-butyllithium (n-butyllithium concentration: 15% by weight) (Merck Company 11) was added to the reagent Ti (h (anatase type) (manufactured by Wako Pure Chemical Industries, Ltd.) 12.011). 91Q was added, and the mixture was left to stand at room temperature in an argon stream for 24 hours, washed with ethanol, and dried to obtain a metal oxide ion conductor. The composition of the obtained conductor was Li, 7Tio2. Then, the apparent diffusion coefficient of lithium ions was measured in the same manner as in Example 1. The results are shown in Table 1.

Table 1 shows that the unfired metal oxide ionic conductor synthesized by the production method of the present invention has an apparent diffusion coefficient of lithium ions nearly an order of magnitude higher than that of the conventional material, and the It turned out to be nearly double digits higher.

[Effects of the Invention] According to the method of the present invention, at the same time as the metal oxide that is the host material is synthesized, at least one of the alkali ions and halogen anions that are the guest ions can be uniformly doped into the oxide. Since fine particles of a metal oxide-based ionic conductor having a uniform particle size can be obtained by a single reaction, the metal oxide-based ionic conductor having a high ion diffusion coefficient can be easily dispersed.

Claims (1)

[Claims] (1) At least one of metal alkoxides, metal β-diketone type organic substances, and mixtures of metal alkoxides and metal β-diketone type organic substances, and at least one type of alkali metal salts and metal halides in a solvent. A metal oxidation method comprising the step of hydrolyzing at least one of a metal alkoxide, a metal β-diketone type organic substance, and a mixture of a metal alkoxide and a metal β-diketone type organic substance after coexisting therein. Manufacturing method for physical ionic conductors.