JP2001114521A - Manganese oxide and its production method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manganese tetroxide belonging to a tetragonal system, having a high purity and a high tapping density, and a method for producing the same. SOLUTION: The trimanganese tetroxide according to the present invention is formed by reacting a manganese ion with a complexing agent in an aqueous solution to form a manganese complex salt, and reacting the manganese complex salt with an alkali metal hydroxide to form manganese hydroxide. Which is produced by reacting the manganese hydroxide with an oxidizing agent, belongs to a tetragonal system, has high purity and high tapping density.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a tetragonal system,
The present invention relates to a high purity and high tapping density manganese tetroxide and a method for producing the same.

[0002]

2. Description of the Related Art A high-purity manganese oxide having a high density and a low impurity content is required as a raw material for an active material for a high-performance battery. Although high-density electrolytic manganese dioxide is known as such manganese oxide, there is a problem that the cost is high due to many and complicated manufacturing steps. In addition, although trimanganese tetroxide is partially produced and used, a conventionally known production method obtains manganese tetroxide with high purity and high tapping density required as a raw material for an active material for a high-performance battery. Was not enough. That is, conventionally, manganese tetroxide has a hydroxide, sulfate, carbonate or the like of manganese of about 1000 in air or oxygen atmosphere.
Heating at a high temperature of 10 ° C.
Although it is produced by heating at a high temperature of 50 ° C., it is difficult to obtain a high-purity product because manganese trioxide as a by-product is mixed.

[0003]

SUMMARY OF THE INVENTION The present invention relates to a high-purity (that is, low-manganese sesquioxide as an impurity) which can not be produced by the conventional method and can be used as a raw material for a high-performance battery. ) And high density (that is, high tapping density) and a method for producing the same.

[0004]

Means for Solving the Problems The present inventors have formed manganese hydroxide from a manganese complex formed in an aqueous solution, and oxidized the obtained manganese hydroxide in an aqueous solution with an appropriate oxidizing agent to produce manganese hydroxide as an impurity. It has been found that a tetragonal trimanganese tetraoxide having a low amount of manganese trioxide and a high tapping density can be obtained.

That is, the present invention provides a tetragonal manganese oxide of high purity and high tapping density which belongs to the tetragonal system.

Further, the trimanganese tetroxide according to the present invention is characterized in that the tapping density is 1.6 g / cc or more.

Further, the trimanganese tetroxide according to the present invention contains (22)
2) The peak intensity of the plane is (10
3) The peak intensity of the surface is 1% or less.

The method for producing tetragonal manganese oxide of high purity and high tapping density according to the present invention comprises reacting a manganese ion with a complexing agent in an aqueous solution to form a manganese complex salt. Reacting the manganese complex with an alkali metal hydroxide to form manganese hydroxide, and reacting the manganese hydroxide with an oxidizing agent to obtain trimanganese tetroxide.

Further, in the method for producing trimanganese tetroxide according to the present invention, the complexing agent may be at least one selected from the group consisting of ammonia, hydrazine, ethylenediaminetetraacetic acid, nitrilotriacetic acid, uracil diacetate, and glycine. It is characterized by one.

The method for producing trimanganese tetroxide according to the present invention is characterized in that the oxidizing agent is at least one selected from the group consisting of oxygen, perchlorate and chlorate. It is.

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

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Manganese tetroxide The manganese tetroxide of the present invention belongs to a tetragonal system by X-ray diffraction and has a spherical shape with an average particle size of 10 to 15 μm.
Further, it is crystalline showing a relatively regular arrangement and has a tetragonal spinel structure. The pores are mesopores (me
sopore) structure, which is an intermediate crystal structure between a tunnel structure and a layered structure. Such a property is suitable as a positive electrode material for a lithium ion secondary battery.

Further, the content of the impurity, manganese trioxide, is determined by X-ray diffraction such that the peak intensity of the (222) plane belonging to trimanganese dioxide is one of the peak intensity of the (103) plane belonging to trimanganese tetraoxide. % Or less. In the case of trimanganese tetroxide obtained by the conventional manganese dioxide firing method, the peak intensity of the (222) plane of the manganese trioxide is extremely low as compared with about 5%, and as an active material for a high-performance battery. It is of sufficient purity.

The manganese tetroxide of the present invention further exhibits a high tapping density, and has at least 2.2 g / g.
More than cc. About 1.4 g / cc of manganese tetroxide produced by the conventional manganese dioxide firing method
Compared to the following, the density is sufficient as an active material for a high-performance battery. Thus, when used as a positive electrode material for a lithium secondary battery, the obtained positive electrode active material has a higher density, the packing density in the battery has been improved, and the unit volume due to the increased amount of the positive electrode active material in the battery has been increased. Per discharge capacity is improved. Production Method A method for producing tetragonal trimanganese oxide of high purity and high tapping density, which belongs to the tetragonal system according to the present invention, comprises first reacting a manganese ion with a complexing agent in an aqueous solution to form a manganese complex salt. Is reacted with an alkali metal hydroxide to form manganese hydroxide particles, and is further reacted with an oxidizing agent in an aqueous solution during or after the production of the manganese hydroxide to obtain trimanganese oxide particles. It is assumed that. (1) The raw material of manganese ions that can be used is not particularly limited as long as manganese ions generated in an aqueous solution can form a complex with a complexing agent. Manganese ion raw materials that can be preferably used include manganese sulfate, manganese nitrate, and manganese chloride. The concentration of the aqueous solution used for the reaction is 10 to 80%, more preferably 20 to 80%.

In the present invention, examples of the complexing agent which forms a complex with manganese ions in an aqueous solution include ammonia, an ammonium ion supply, hydrazine, ethylenediaminetetraacetic acid, nitritoacetic acid, uracil diacetate, and glycine. Examples of the ammonium ion supply include ammonium sulfate, ammonium chloride, and ammonium acetate, which need to be neutralized using a suitable alkali.
The concentration of the complexing agent is such that the complex is sufficiently formed and the p
The amount is preferably 1 to 6 mol with respect to the manganese ion so that H is not greatly changed.

The conditions for the complex formation reaction are not particularly limited, but the manganese salt aqueous solution and the complexing agent aqueous solution are continuously added to a reaction vessel having a sufficient volume with stirring, and the mixture is reacted. The reaction temperature is not particularly limited, but the temperature in the aqueous solution is 10 to 90 ° C, preferably 30 to 60 ° C.
Is preferably maintained. When neutralization is required, an alkali can be added in advance or simultaneously.
The reaction is almost completed in the same manner as the mixing, but it is also preferable to stir for several hours to complete the complex formation reaction. The reaction can be easily monitored, for example, by measuring the characteristic UV / VIS absorption spectrum of the resulting complex.

(2) In the present invention, the pH of the complex in the solution produced in the above (1) is adjusted to 8 to 12, preferably 9 to 12 with a metal hydroxide, so that manganese hydroxide ( Particles). Examples of such a metal hydroxide include sodium hydroxide and potassium hydroxide. In the manganese hydroxide (particle) forming step, it is preferable to stir the solution and maintain the reaction temperature at 10 ° C to 90 ° C, preferably 30 ° C to 60 ° C. The process of particle formation and particle size include the shape of the reaction vessel, stirring method, concentration of reactants in the reaction solution, reaction time, reaction temperature,
Depending on the pH of the solution during the reaction, etc., it is easy for those skilled in the art to appropriately select and optimize these reaction conditions. For example, when the temperature is low, the reaction does not proceed sufficiently, resulting in incomplete crystals. On the other hand, when the temperature is too high, the reaction speed increases, and the particles do not grow sufficiently, resulting in low density particles. The reaction time is preferably from 10 hours to 50 hours. The pH at the time of the reaction can be 8 or more, but it is particularly preferably 9 to 12. (3) The present invention is characterized in that the manganese hydroxide particles in the solution produced in the above (2) are further oxidized with an oxidizing agent in an aqueous solution at a relatively low temperature to obtain trimanganese oxide. Things. As the oxidation treatment using the oxidizing agent, a method of blowing ozone gas, oxygen gas, or a mixed gas containing oxygen (including air) into a solution is possible. Further, a method of adding an aqueous solution of an oxidizing agent such as perchlorate or chlorate is possible.

After the obtained trimanganese tetroxide is separated, it can be dried by heating, for example, with a cylindrical rotary drier.
The purity of manganese tetroxide (contained manganese trioxide) obtained by the production method according to the present invention can be analyzed by X-ray diffraction. Here, it is particularly preferable to quantify the peak intensity of the (222) plane belonging to manganese trioxide and the peak intensity of the (103) plane belonging to trimanganese tetroxide. Further, the tapping density is not limited to a usual measuring method. For example, a commercially available tapping density measuring instrument can be preferably used.

Lithium manganese composite oxide and spinel lithium manganese oxide LiMn ₂ O as a positive electrode active material for a lithium ion secondary battery, obtained by mixing and firing a lithium salt using the trimanganese tetroxide of the present invention. ₄ , orthorhombic LiMnO ₂ and voltage 3V Li ₂ Mn ₄ O ₉ ,
It can be used as a raw material such as Li ₄ Mn ₅ O ₁₂ .

Hereinafter, the present invention will be described in more detail with reference to Examples, but it should not be construed that the invention is limited thereto.

[0021]

EXAMPLES Example 1 10 L of water was charged into a 15 L cylindrical reaction tank equipped with a stirrer, and the temperature was maintained at 60 ° C. There, 1L of 20% manganese sulfate aqueous solution and 0.1L of 5%
% Aqueous ammonia solution was added and mixed with stirring. Further, the pH of the reaction solution was adjusted to 9.0 by adding 0.5 L of a 20% sodium hydroxide solution to form manganese hydroxide particles. After the manganese hydroxide particles were generated, the mixture was stirred for 5 hours while bubbling oxygen gas at 0.2 L / min. The obtained trimanganese tetroxide particles were collected by filtration. Further, it was dried in a hot air atmosphere at 100 ° C. for 10 hours.

The obtained manganese tetroxide (sample 1) was analyzed by X-ray diffraction as follows. Preparation of sample: The trimanganese tetroxide particles obtained above were used as they were. Measuring device and condition: RINT2000, manufactured by Rigaku Corporation
(Cu-Kα) Measurement result: Almost no peak was observed on the manganese trioxide (222) plane.

The tapping density of the obtained trimanganese tetroxide was measured as follows. Sample preparation: The trimanganese tetroxide particles obtained above were used as follows.
The mass of the 20 mL cell [C] was measured [A], and the crystal was naturally dropped into the cell with a 48 mesh screen and filled. "TAPE" manufactured by Seishin Enterprise Co., Ltd. with 4cm spacer
After tapping 200 times using "NSER KYT3000", the mass [B] and the filling volume [D] of the cell were measured. It was calculated by the following equation. Tap density = (BA) / D g / ml Bulk density = (BA) / C g / ml Measurement result: 1.65 g / cc The average particle size of the obtained manganese tetroxide is as follows. It was measured. Preparation of sample: The trimanganese tetroxide particles obtained above were used as they were. Measurement device and conditions: Using LA-910 manufactured by Horiba,
The operating procedure was followed. Measurement result: 12.0 μm (Examples 2 and 3) Manganese manganese oxide was produced under the same conditions as in Example 1 except that the pH of the reaction solution for forming manganese hydroxide particles was 10.0 and 11.0. Then, X-ray diffraction analysis and tapping density measurement were performed. Sample 2,
3 is assumed.

As a result, no peak on the manganese trioxide (222) plane was observed from the X-ray diffraction results. The tapping densities are 1.70 g / cc and 1.68 g / cc, respectively.
cc. Comparative Example 1 A commercially available heavy manganese carbonate having a tapping density of 2.0 g / cc was heated at 1000 ° C. in air for 5 hours. Physical properties were measured in the same manner as in Example 1. The obtained manganese tetroxide is a spinel-based body-centered square lattice with a distorted crystal form, and a tapping density of 1.42 g / cc.
(Referred to as sample 4). (Comparative Example 2) A mixed crystal having a tunnel structure of 1 × 1 (Pyrolusite or β-MnO ₂ ) and 2 × 1 (Ramsdelite) and a tapping density of 2.0 g / c
c) electrolytic manganese dioxide in air at 1050 ° C.
Heated for hours. Physical properties were measured in the same manner as in Example 1. The obtained manganese tetroxide is a spinel body-centered square lattice with a distorted crystal form, and a tapping density of 1.
It was 80 g / cc (sample 5). (Example 4) Samples 1, 2, 3, 4, and 5 obtained in Examples 1, 2, and 3 and Comparative Examples 1 and 2 were each prepared by adding lithium hydroxide having a molar ratio of manganese to lithium of 2.0: 1. And mixed well. The obtained mixture is placed in a firing furnace for 75 hours.
The resultant was calcined and oxidized at 0 ° C. for 12 hours in an air stream to obtain spinel lithium manganate (LiMn ₂ O ₄ ).

The powder of the obtained sample, the conductive agent carbon black and the binder fluorocarbon resin were mixed in a weight ratio of 85:
The mixture was mixed at a ratio of 7.5: 7.5, and compressed at a pressure of 2 ton / cm 2 to form a pellet having a diameter of 15 mm. The negative electrode was made of a Li-Al alloy under an argon atmosphere and had a thickness of 0.3 mm.
, And punched out into a disk having a diameter of 15 mm to obtain a negative electrode.

As the electrolyte, a non-aqueous electrolyte prepared by adding LiPF6 to a solution of ethylene carbonate: propylene carbonate = 1: 1 was used.

The charge / discharge cycle test, the initial discharge capacity test, and the like were performed at a constant current of 20 ° C. and 1 mA, and the upper limit of charge was 4.3.
V and discharge lower limit voltage of 2.8 V, respectively, and charging and discharging were repeated. The initial discharge capacity of each sample was compared when the initial discharge capacity was set to 100 using a spinel-based lithium manganate sample synthesized from the following electrolytic manganese dioxide as a positive electrode (Comparative Example 3). As a result, Sample 1,
120, 118, 115, 9 at 2, 3, 4, 5 respectively
4,97. (Comparative Example 3) Lithium hydroxide monohydrate was added to electrolytic manganese dioxide so that the molar ratio of manganese to lithium was 2: 1.1 and mixed well. The obtained mixture is heated in a firing furnace for 7 hours.
The resultant was calcined and oxidized at 50 ° C. for 12 hours in an air stream to obtain spinel lithium manganate (LiMn ₂ O ₄ ). A positive electrode for a lithium battery was prepared in the same manner as in Example 4.

[0028]

The manganese tetroxide according to the present invention is prepared by reacting a manganese ion with a complexing agent in an aqueous solution to form a manganese complex, and reacting the manganese complex with an alkali metal hydroxide to form a hydroxide. It is produced by producing manganese and reacting the manganese hydroxide with an oxidizing agent, belongs to a tetragonal system, has a low content of manganese trioxide and is at least 1.6 g / cc or more. High tapping density.

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Claims (6)

[Claims] 1. A manganese tetraoxide having a high purity and a high tapping density, which belongs to a tetragonal system. 2. The manganese tetroxide according to claim 1, wherein the tapping density is 1.6 g / cc or more. 3. The peak intensity of the (222) plane of manganese trioxide contained as an impurity is 1% or less of the peak intensity of the (103) plane of trimanganese tetroxide. 3. Manganese tetroxide according to any one of 2. 4. A manganese ion is reacted with a complexing agent in an aqueous solution to form a manganese complex, and the manganese complex is reacted with an alkali metal hydroxide to produce manganese hydroxide. A process for producing tetramanganese manganese oxide having a high purity and a high tapping density, which belongs to a tetragonal system, wherein manganese tetraoxide is obtained by reacting an oxidizing agent. 5. The complexing agent according to claim 4, wherein the complexing agent is at least one selected from the group consisting of ammonia, hydrazine, ethylenediaminetetraacetic acid, nitrilotriacetic acid, uracildiacetate, and glycine. the method of. 6. The method according to claim 4, wherein the oxidizing agent is at least one selected from the group consisting of oxygen, perchlorate and chlorate.