JP2003020298A - Method for manufacturing metal oxide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for preparing single crystals of metal oxides by using vaporizable metal salts. SOLUTION: In the method for manufacturing the metal oxides, smoke produced in the vaporizing process of metal salts which vaporize at high temperature is introduced into a reaction field with a controlled atmosphere so as to allow an oxidation reaction to proceed to produce crystal grains of oxides. The metal salt which vaporizes at high temperature is lithium chloride, manganese chloride or cobalt chloride. The oxidation reaction is controlled by the pressure of oxygen to produce the crystal grains of oxides of required oxidation numbers. Compound oxides can be produced by introducing two or more kinds of smoke into the reaction field.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for preparing a manganese oxide single crystal which can be used as a material useful in battery engineering.

[0002]

2. Description of the Related Art High energy density and high power density are desired for small portable electronic devices, power sources for electric vehicles and the like. At present, a new type of energy device called an electrochemical capacitor using a metal oxide as an electrode material is drawing attention. A series of oxides of noble metals, valve metals, transition metals, and lithium transition metals are used as energy storage materials for metal oxide materials. Among these, valve metals are used as electrolytic capacitor materials, and other metals are used as electrode materials for electrochemical capacitors and various batteries.

The growth of a single crystal of a metal oxide is generally carried out by dissolving the oxide at a high temperature and then gradually cooling it. However, transition metal oxides such as LiMO ₂ (M = Mn, Co,
V, Ni) and LiMn ₂ O ₄ have a very low solubility in the valence state of transition metal ions, and their solubility is extremely low.
It is difficult to grow a single crystal by an ordinary cooling method. Up to now, an attempt to grow a single crystal of Li ₂ MnO ₃ by the molten salt method has been reported, but no single crystal growth example regarding other transition metal oxides is found. The present inventors have made use of manganese oxides (LiMn ₂ O ₄ , Li ₂ MnO _3, etc.) that can be used as materials useful for battery engineering such as secondary battery materials.
For the purpose of providing a single crystal, a patent has already been filed for a method for producing a manganese oxide single crystal by growing a manganese oxide single crystal by a high temperature molten salt method (Japanese Patent Application No. 2000-13460).
2).

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for preparing a metal oxide single crystal using an evaporative metal salt.

[0005]

[MEANS FOR SOLVING THE PROBLEMS] The present invention is a metal for introducing smoke generated in the evaporation process of a metal salt that evaporates at a high temperature into a reaction field whose atmosphere is controlled to promote an oxidation reaction to generate oxide crystal particles. It is a method for producing an oxide.

The high temperature evaporating metal salt is lithium chloride, manganese chloride or cobalt chloride, in which case the present invention occurs in the evaporation process of the high temperature evaporating metal salt consisting of lithium chloride, manganese chloride or cobalt chloride. This is a method for producing a metal oxide in which smoke is introduced into a reaction field whose atmosphere is controlled to promote an oxidation reaction to generate oxide crystal particles.

Oxidation pressure is controlled by oxygen pressure to generate oxide crystal particles having a required oxidation number. In that case,
The present invention, a metal salt that evaporates at a high temperature, more specifically, lithium chloride, manganese chloride or cobalt chloride is introduced into the reaction field controlled atmosphere atmosphere smoke to proceed the oxidation reaction, at that time, This is a method for producing a metal oxide in which an oxidation reaction is controlled by oxygen pressure to generate oxide crystal particles having a required oxidation number.

A complex oxide is produced by introducing two or more kinds of smoke into the reaction field. In that case,
The present invention introduces a metal salt that evaporates at a high temperature, more specifically, two or more kinds of smoke generated in the evaporation process of lithium chloride, manganese chloride or cobalt chloride into an atmosphere-controlled reaction field to promote an oxidation reaction. This is a method for producing a metal oxide in which a composite oxide is produced and, when necessary, an oxidation reaction is controlled by oxygen pressure to produce oxide crystal particles having a required oxidation number.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION [Raw Material Compound] As the metal compound as a raw material compound, known compounds can be used.
It must be a salt that evaporates at high temperatures. For example, chloride salts and fluoride salts of lithium, manganese, cobalt and the like can be mentioned.

[Composition of Product and Morphology Control] The composition of the product can be controlled by selecting the kind of the raw material compound, as well as by controlling the heating temperature and atmosphere. For example, when MnO ₂ is prepared using MnCl ₂ , a relatively low temperature of 650 ° C. or lower is preferable in a strong oxidizing atmosphere, whereas when adjusting Mn ₂ O ₃ , a high temperature is preferable. The reaction field allows the preparation of fine nano-sized particles to milli-sized single crystals. In this case, the design of the reaction field is important. From the viewpoint of the formation and growth of crystal nuclei, the growth of single crystal particles is preferably a system capable of continuously supplying smoke to a fixed reaction field. On the other hand, in order to prepare fine nano-sized particles, it is desirable that the smoke reacts while flowing in the reaction field from the viewpoint of suppressing particle growth.

[Heating Temperature] To obtain an oxide, a metal salt or a sufficiently mixed mixture thereof may be heated. The heating temperature may be higher than the melting point of the metal salt used, but in the case of transition metal oxides such as manganese and iron, the temperature is important because the valence of the metal is greatly influenced by the temperature.

[Atmosphere] In order to obtain an oxide, a reaction in air is possible, but in order to obtain a specific oxide, it is important to control the oxygen partial pressure. The atmosphere can be controlled by introducing oxygen gas, nitrogen gas, or a mixed gas thereof, but it can also be controlled by adding an oxidizing-reducing reagent to the molten salt.

[0013]

[Function] The oxide single crystal particles are generally grown by dissolving the oxide at a high temperature and then gradually cooling. However, transition metal oxides such as LiMO2 (M = Mn, Co, V, N
In the case of i) and LiMn ₂ O ₄ , the valence state of the transition metal ion depends on the temperature and the solubility thereof is extremely low, so that it is difficult to form a single crystal by a usual cooling method. The present invention utilizes evaporative metal salts to prepare metal oxide single crystals.

It is known that metal salts such as lithium chloride, manganese chloride and cobalt chloride evaporate at high temperatures.
When the smoke generated in the evaporation process is introduced into a reaction field where the atmosphere is controlled and reacted, oxide crystal particles can be generated. For example, when manganese chloride is heated at a melting point of 650 ° C. or higher, it vaporizes and produces MnCl ₂ smoke. When the smoke is introduced into the reaction field to promote the oxidation reaction, Mn ₂ O ₃ , Mn ₃ O ₄ and MnO ₂ are obtained by the oxygen pressure. Also,
A complex oxide can be produced by introducing two or more kinds of smoke into the reaction field. For example, LiCl and MnCl
Evaporation of the ₂ mixed molten salt, LiMn ₂ O ₄ is obtained.

[0015]

The details of the present invention will be described with reference to Examples. The present invention is not limited to these examples.

Example 1 MnCl2.4H2O was dissolved in 5 ml of distilled water,
50 g of LiCl was added. After mixing well, 180
It dried at 5 degreeC for 5 hours. After that, the mixture was finely crushed in a mortar and transferred to an alumina crucible. The mixture was further covered with 20 g LiCl in order to prevent rapid evaporation and oxidation reaction of the LiCl-MnCl2 molten salt, and the mixture was set in an electric furnace.
Heat at 750 for 5 days. After completion of heating, the single crystal of interest is obtained by dissolution and washing. The obtained single crystal is M in the mixture.
When the content of n is 4 mmol, it is a single crystal particle of about 0.1 mm (FIG. 1), but when it is 18 mmol,
It is a large crystal body of about 1 mm (FIG. 2).

Example 2 20 g of MnCl2.4H2O was placed in an alumina crucible,
Heat at 650 ° C. for 12 hours. Needle-shaped Mn _{2 on the} crucible wall
O ₃ crystals (FIG. 3) formed. When this needle-like crystal was enlarged, it was found that the single crystal particles were connected and formed (FIG. 4).

Example 3 2 g of CoCl 2 was dissolved in 5 ml of distilled water,
g of LiCl was added. After mixing well, it was dried at 180 ° C. for 5 hours. Then crush the mixture in a mortar,
It was transferred to an alumina crucible. 20 g LiCl on top of the mixture
It was covered with and set in an electric furnace. Heat at 650 for 5 days. After completion of heating, the single crystal of interest is obtained by dissolution and washing.
The obtained crystal was Co ₂ O ₃ and had a size of about 0.1 mm (FIG. 5).

[0019]

EFFECT OF THE INVENTION It can be used as a useful material in battery engineering.
Manganese oxide (LiMn₂O_Four, Li ₂MnO₃Etc.)
Crystals can be provided.

[Brief description of drawings]

FIG. 1 is an Mn oxide produced in Example 1 (Mn content: 4
2 is an electron micrograph replacing a drawing of a single crystal particle (in the case of mmol).

2 is an Mn oxide produced in Example 1 (Mn content: 1
It is an electron microscope photograph replacing a drawing of a single crystal particle (in the case of 8 mmol).

FIG. 3 is an electron micrograph as a drawing substitute for a needle-like Mn ₂ O ₃ crystal produced in Example 2.

FIG. 4 is an electron micrograph taken in lieu of the enlarged view of FIG. 3 showing that single crystal particles are formed to be connected.

FIG. 5 is an electron micrograph replacing a drawing of a Co ₂ O ₃ single crystal.

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[Procedure amendment]

[Submission date] July 4, 2001 (2001.7.4)

[Procedure Amendment 1]

[Document name to be corrected] Drawing

[Correction target item name] All drawings

[Correction method] Change

[Correction content]

[Figure 1]

[Fig. 2]

[Figure 3]

[Figure 4]

[Figure 5]

─────────────────────────────────────────────────── ─── Continued Front Page (51) Int.Cl. ⁷ Identification Code FI Theme Coat (Reference) H01M 4/50 H01M 4/50 4/52 4/52 4/58 4/58 (72) Inventor Kenta Oi 2217-14 Hayashi-cho, Takamatsu-shi, Kagawa F-term in Shikoku Center, National Institute of Advanced Industrial Science and Technology (reference) 4G077 AA01 AA04 BB10 BC60 DA17 EA07 SA02 SA08 5H050 CA05 CA09 FA19 GA02 GA15 GA27

Claims (4)

[Claims] 1. A method for producing a metal oxide, wherein smoke produced in the evaporation process of a metal salt that evaporates at a high temperature is introduced into a reaction field whose atmosphere is controlled to promote an oxidation reaction to generate oxide crystal particles. 2. The metal salt which evaporates at high temperature is lithium chloride,
The method for producing a metal oxide according to claim 1, which is manganese chloride or cobalt chloride. 3. The method for producing a metal oxide according to claim 1, wherein the oxidation reaction is controlled by oxygen pressure to generate oxide crystal particles having a required oxidation number. 4. The method for producing a metal oxide according to claim 1, 2 or 3, wherein a complex oxide is produced by introducing two or more kinds of smoke into the reaction field.