WO2013115335A1 - Electrolytic manganese dioxide, method for producing same, and use of same - Google Patents

Abstract

Provided are an electrolytic manganese dioxide with which contamination by metal impurities during industrial production steps can be prevented, that is, an electrolytic manganese dioxide having excellent pulverization properties, and a method for producing the same. The electrolytic manganese dioxide has an apparent particle density of 3.0 g/cm³ or greater, a particle density of 4.25 g/cm³ or greater, and preferably a porosity of 0.01 mL/g or greater. The electrolytic manganese dioxide is produced by mixing an amorphous manganese oxide in an electrolyte solution.

Description

Electrolytic manganese dioxide, method for producing the same, and use thereof

The present invention relates to electrolytic manganese dioxide that is used as a raw material for, for example, a positive electrode active material for a lithium secondary battery, and a method for producing the same.

Electrolytic manganese dioxide is widely used as a positive electrode active material for primary batteries such as alkaline batteries or as a raw material for lithium manganese composite oxides that are positive electrode active materials for lithium ion secondary batteries. Compared to electrolytic manganese dioxide used as a positive electrode active material for primary batteries, electrolytic manganese dioxide used as a positive electrode material for lithium secondary batteries is required to further reduce metal impurities.

In order to reduce metal impurities in electrolytic manganese dioxide, it is considered effective to improve the grinding characteristics. That is, agglomerated electrolytic manganese dioxide is deposited on the electrolytic electrode by electrolysis (electrolysis) of an electrolytic solution containing manganese ions, and this is pulverized to form a powder. (For example, Patent Documents 1 to 3). Metal impurities are mixed when the agglomerated electrolytic manganese dioxide is pulverized. Accordingly, by improving the pulverization characteristics of electrolytic manganese dioxide, that is, by making electrolytic manganese dioxide easily pulverizable, mixing of metal impurities due to pulverization can be suppressed.

So far, regarding the grinding characteristics of electrolytic manganese dioxide, it has been reported that the grinding characteristics are improved by increasing the BET specific surface area, and that other physical properties of electrolytic manganese dioxide do not affect the grinding characteristics. (Non-Patent Document 1).

Japanese Unexamined Patent Publication No. 11-126607 Japanese Patent Publication No.57-42711 Japanese Unexamined Patent Publication No. 51-104499

The conventional easily pulverized electrolytic manganese dioxide has a high BET specific surface area. However, such electrolytic manganese dioxide has a low filling property. On the other hand, electrolytic manganese dioxide having a high filling property is a strong electrolytic manganese dioxide, and thus has poor grinding characteristics and is difficult to grind. Thus, conventional electrolytic manganese dioxide has either excellent grinding characteristics or excellent filling properties, and electrolytic manganese dioxide satisfying both of these has not been obtained.

An object of the present invention is to solve these problems and to provide an electrolytic manganese dioxide excellent in pulverization characteristics and excellent in filling properties and a method for producing the same.

The inventors of the present invention have made extensive studies on electrolytic manganese dioxide having excellent grinding characteristics. As a result, it has been found that electrolytic manganese dioxide having an apparent particle density and particle density different from the conventional ones has high filling properties and is easily pulverized. Furthermore, the present inventors have found that such electrolytic manganese dioxide can be produced by an electrolysis method different from the conventional one, and have completed the present invention.

That is, the gist of the present invention is as follows.
(1) An electrolytic manganese dioxide having an apparent particle density of 3.0 g / cm ³ or more and a particle density of 4.25 g / cm ³ or more.
(2) The electrolytic manganese dioxide as described in (1) above, wherein the open pores are 0.01 mL (liter) / g or more.
(3) The electrolytic manganese dioxide as described in (1) or (2) above, wherein the BET specific surface area is 10 m ² / g or more and 45 m ² / g or less.
(4) The method for producing electrolytic manganese dioxide as described in any one of (1) to (3) above, wherein amorphous manganese oxide is mixed in an electrolytic solution.
(5) The method for producing electrolytic manganese dioxide as described in (4) above, wherein amorphous manganese oxide is produced in the electrolytic solution, and the amorphous manganese oxide is mixed in the electrolytic solution.

(6) The method for producing electrolytic manganese dioxide as described in (4) or (5) above, wherein amorphous manganese oxide is mixed in the electrolytic solution by dissolution and reprecipitation of the manganese compound in the electrolytic solution. .
(7) The method for producing electrolytic manganese dioxide as described in (6) above, wherein the manganese compound is a crystalline manganese oxide.
(8) The method for producing electrolytic manganese dioxide as described in (6) or (7) above, wherein the manganese compound is a crystalline manganese oxide having a manganese oxidation degree of 1 or more and 1.6 or less.
(9) The method for producing electrolytic manganese dioxide as described in any one of (6) to (8) above, wherein the manganese compound is a chemical manganese oxide.
(10) The method for producing electrolytic manganese dioxide as described in any one of (6) to (9) above, wherein the manganese compound is trimanganese tetraoxide or manganese trioxide or both.

(11) The electrolytic manganese dioxide production according to any one of (4) to (10) above, wherein the concentration of amorphous manganese oxide in the electrolytic solution is 0.5 mg / L or more and 20 mg / L or less Method.
(12) The method for producing electrolytic manganese dioxide as described in any one of (4) to (11) above, wherein the amorphous manganese oxide has a BET specific surface area of 80 m ² / g or more.
(13) The method for producing electrolytic manganese dioxide as described in any one of (4) to (12) above, wherein the electrolytic solution is a mixed solution of sulfuric acid and manganese sulfate.
(14) The electrolytic manganese dioxide production method as described in any one of (4) to (13) above, wherein the electrolytic current density is 0.5 A / dm ² or more and 1.5 A / dm ² or less.
(15) A lithium manganese composite oxide obtained by using the electrolytic manganese dioxide according to any one of (1) to (3).

The electrolytic manganese dioxide of the present invention has not only high filling properties but also easy grindability. Therefore, pulverization with less pulverization energy becomes possible. Furthermore, the pulverization time can be shortened. Thereby, it can be expected that metal impurities are prevented from being mixed from equipment in the manufacturing process. Thereby, the electrolytic manganese dioxide suitable for the positive electrode material for alkaline batteries, the manganese raw material for secondary battery materials, etc. with high filling property and few metal impurities can be provided industrially stably. Furthermore, such easily pulverizable electrolytic manganese dioxide can be easily industrially produced by the production method of the present invention.

X-ray powder diffraction (XRD) diagram of trimanganese tetraoxide obtained in Example 1 Powder X-ray diffraction pattern of amorphous manganese oxide obtained in Example 1 Pore size distribution diagram of electrolytic manganese dioxide obtained in Example 2 and Comparative Example 3 (in the figure, solid line is Example 2 and broken line is Comparative Example 3) SEM observation result of electrolytic manganese dioxide obtained in Example 2 (scale in the figure is 10 μm)

SEM observation result of electrolytic manganese dioxide obtained in Comparative Example 2 (scale in the figure is 10 μm) SEM observation result of electrolytic manganese dioxide obtained in Comparative Example 3 (scale in the figure is 10 μm) Powder X-ray diffraction pattern of manganese oxide in manganese oxide slurry of Comparative Example 5 Powder X-ray diffraction pattern of manganese oxide in the electrolyte solution of Comparative Example 5

Hereinafter, the electrolytic manganese dioxide of the present invention will be described.
The electrolytic manganese dioxide of the present invention has a particle density of 4.25 g / cm ³ or more and an apparent particle density of 3.0 g / cm ³ or more. When either one of the particle density and the apparent particle density satisfies the above range, the filling properties of electrolytic manganese dioxide are enhanced. Furthermore, the electrolytic manganese dioxide of the present invention satisfies both the particle density and the apparent particle density in the above range. As a result, the electrolytic manganese dioxide of the present invention becomes electrolytic manganese dioxide having high grinding characteristics, that is, easily grindable electrolytic manganese dioxide.

In addition, the apparent particle density in this invention is a density calculated | required on the basis of the volume of electrolytic manganese dioxide particles. That is, the apparent particle density is the density of particles when it is considered that closed pores and open pores do not exist in the electrolytic manganese dioxide particles.
On the other hand, the particle density is a density obtained by excluding open pores from the volume of electrolytic manganese dioxide particles. That is, the density of the particles when the open pores are present in the electrolytic manganese dioxide particles but the closed pores are not present is the particle density.
The apparent particle density and the particle density can be determined by a mercury intrusion method, for example, a method described in Examples described later.

Apparent particle density of electrolytic manganese dioxide of the present invention is 3.0 g / cm ³ or more, preferably 3.5 g / cm ³ or more, more preferably 3.8 g / cm ³ or more, 4 More preferably, it is 0.0 g / cm ³ or more. When the apparent particle density is less than 3.0 g / cm ³ , the electrolytic manganese dioxide becomes porous particles. On the other hand, when the apparent particle density is 4.5 g / cm ³ or less, the electrolytic manganese dioxide has a sufficiently high filling property.

Particle density of electrolytic manganese dioxide of the present invention is 4.25 g / cm ³ or more, preferably 4.3 g / cm ³ or more, and more preferably 4.4 g / cm ³ or more. When the particle density is less than 4.25 g / cm ³ , electrolytic manganese dioxide becomes particles containing many closed pores. On the other hand, the theoretical density of electrolytic manganese dioxide is 4.8 g / cm ³ . Therefore, the particle density of the electrolytic manganese dioxide of the present invention is at most 4.8 g / cm ³ or less.

Thus, both the particle density and the apparent particle density indicate the filling properties of electrolytic manganese dioxide. When any of these satisfies the scope of the present invention, the electrolytic manganese dioxide of the present invention has a high filling property. In addition, when both the particle density and the apparent particle density satisfy the scope of the present invention, the electrolytic manganese dioxide of the present invention becomes an easily pulverizable electrolytic manganese dioxide having excellent grinding characteristics.

Furthermore, the electrolytic manganese dioxide of the present invention preferably has an open pore of 0.01 mL / g or more, more preferably 0.015 mL / g or more, and further preferably 0.02 mL / g or more. 0.026 g / mL / g or more is even more preferable, and 0.03 mL / g or more is particularly preferable. When the open pores are 0.01 mL / g or more, the electrolytic manganese dioxide is more easily pulverized. On the other hand, when the number of pores in the electrolytic manganese dioxide increases, the particle density tends to decrease. Examples of the open pores for having an appropriate particle density include at most 0.07 mL / g or less, and further 0.06 mL / g or less. The amount of open pores is determined by the difference between the apparent particle density and the inverse of the particle density.

It can be confirmed from the fine structure that the electrolytic manganese dioxide of the present invention is easily pulverizable. That is, most of the pores present in the electrolytic manganese dioxide of the present invention are open pores. Further, these open pores are formed by irregularly connecting individual pores, and the open pores having an irregular shape with a pore diameter (approximate diameter) of 0.2 μm or more when approximated by a cylinder are used. It has become. One of the causes that the electrolytic manganese dioxide of the present invention becomes easily pulverizable is that it has such a fine structure having many open pores having an irregular shape.

Furthermore, the electrolytic manganese dioxide of the present invention has not only fine open pores but also a fine structure with few closed pores, particularly fine particles having almost no coarse closed pores with a pore diameter exceeding 0.2 μm. Structure. Such a small number of coarse closed pores is considered as one of the causes that the electrolytic manganese dioxide of the present invention is not only excellent in pulverization characteristics but also excellent in filling properties. On the other hand, the conventional electrolytic manganese dioxide has a fine structure having almost no open pores having an indefinite shape, and has a fine structure different from the electrolytic manganese dioxide of the present invention.

The difference in microstructure between the conventional electrolytic manganese dioxide and the electrolytic manganese dioxide of the present invention can be observed as a difference in the morphology of electrolytic manganese dioxide using a scanning electron microscope (hereinafter also referred to as SEM). There are cases where it is possible. In particular, the form of the electrolytic manganese dioxide of the present invention has a fine structure having irregularly shaped open pores. This fine structure is confirmed as an aggregate of electrolytic manganese dioxide having a substantially network-like primary structure. Such a substantially network-like primary structure can also be confirmed as finely pulverized electrolytic manganese dioxide powder. In addition to this, in the electrolytic manganese dioxide peeled from the electrode, that is, the so-called chip-like electrolytic manganese dioxide, this substantially network-like primary structure can be observed particularly clearly.

Furthermore, since the electrolytic manganese dioxide of the present invention is easily pulverized, the hardness, which is an indicator of pulverization, is lower than that of conventional electrolytic manganese dioxide. Therefore, the electrolytic manganese dioxide of the present invention preferably has a micro Vickers hardness of Hv = 400 or less, more preferably Hv = 350 or less, and even more preferably Hv = 300 or less.

The electrolytic manganese dioxide of the present invention preferably has a BET specific surface area of 10 m ² / g or more, more preferably 15 m ² / g or more, and further preferably 20 m ² / g or more. When the BET specific surface area is 10 m ² / g or more, the reactivity of electrolytic manganese dioxide tends to be high. On the other hand, when the BET specific surface area becomes higher than necessary, the filling properties of electrolytic manganese dioxide tend to be lowered. Therefore, the BET specific surface area is preferably 45 m ² / g or less, more preferably 40 m ² / g or less, and further preferably 35 m ² / g or less.

Note that conventional electrolytic manganese dioxide with a high BET specific surface area and excellent grinding characteristics has almost no open pores of irregular shape. Therefore, the grinding characteristics of such electrolytic manganese dioxide tend to depend on the BET specific surface area. That is, when the BET specific surface area is increased, the crushing characteristics are increased, while when the BET specific surface area is decreased, the crushing characteristics are decreased. On the other hand, the electrolytic manganese dioxide of the present invention is mainly affected by the hardness of the electrolytic manganese dioxide itself and the irregularly shaped open pores in the grinding characteristics. Therefore, the grinding characteristics of the electrolytic manganese dioxide of the present invention are not easily affected by the BET specific surface area.

The electrolytic manganese dioxide of the present invention has a full width at half maximum (hereinafter simply referred to as “FWHM”) of diffraction lines on the (110) plane in X-ray diffraction measurement of 1.7 ° or more and 4.0 ° or less. Preferably, it is 1.85 ° or more and 3.7 ° or less, and more preferably 2.0 ° or more and 3.5 ° or less. If FWHM is in this range, the reactivity between electrolytic manganese dioxide and lithium compounds tends to be high. In addition, the diffraction line on the (110) plane in the X-ray diffraction measurement can be observed at 2θ around 22 ± 1 ° in the XRD measurement pattern using CuKα rays as a light source.

Next, the manufacturing method of the electrolytic manganese dioxide of this invention is demonstrated.
The present invention is a method for producing electrolytic manganese dioxide, characterized in that amorphous manganese oxide is mixed in an electrolytic solution. That is, the production method of the present invention is a method for producing electrolytic manganese dioxide characterized by electrolyzing an electrolytic solution containing amorphous manganese oxide.

As a method for producing electrolytic manganese dioxide, an electrolytic method in which an electrolytic solution is electrolyzed without using suspended particles (hereinafter referred to as “clarified electrolytic method”), or manganese compound particles are mixed with an electrolytic solution to make the electrolytic solution electrically There is an electrolysis method that decomposes (hereinafter, “suspension electrolysis”). Conventionally, crystalline manganese oxide has been used as manganese compound particles (hereinafter referred to as “suspended particles”) mixed in an electrolytic solution by a suspension electrolysis method. In contrast, the production method of the present invention is a suspension electrolysis method that uses amorphous (non-crystalline) manganese oxide as suspended particles, and substantially uses crystalline manganese oxide as suspended particles. This is a suspension electrolysis method.

Therefore, the production method of the present invention is a method for producing manganese dioxide for electrolyzing an electrolytic solution containing amorphous manganese oxide. By employing a suspension electrolysis method using amorphous manganese oxide as suspension particles, the precipitation state of electrolytic manganese dioxide in the production method of the present invention is the same as the conventional clarification electrolysis method and crystalline manganese oxidation as suspension particles. This is different from the precipitation state of electrolytic manganese dioxide in a suspension electrolytic method using a product, that is, a production method in which an electrolytic solution containing crystalline manganese oxide is electrolyzed. Thereby, easily pulverizable electrolytic manganese dioxide is obtained.

In the production method of the present invention, amorphous manganese oxide is mixed in the electrolytic solution. Thereby, electrolytic manganese dioxide is electrolytically deposited from the electrolytic solution containing amorphous manganese oxide.

The amorphous manganese oxide may be an amorphous manganese oxide. The term “amorphous” means that the full width at half maximum of the diffraction peak having the highest intensity (for example, 2θ = 37 ± 1 ° diffraction peak when CuKα is used as a radiation source) is 1 in powder X-ray diffraction measurement. 0.0 ° or more, and further 1.5 ° or more. Thus, amorphous manganese oxide does not show a clear diffraction peak in powder X-ray diffraction measurement.

The amorphous manganese oxide preferably has a BET specific surface area of 80 m ² / g or more, and more preferably 85 m ² / g or more. It becomes easy to disperse | distribute uniformly in electrolyte solution because the BET specific surface area of an amorphous manganese oxide is 80 m < ² > / g or more.
The degree of manganese oxidation of amorphous manganese oxide (x when manganese oxide is expressed as MnOx) has little influence on the grinding characteristics of the obtained electrolytic manganese dioxide. Therefore, the manganese oxidation degree of amorphous manganese oxide is not particularly limited. As the manganese oxidation degree of the manganese oxide, x can be 1.65 or more.

In the method for producing electrolytic manganese dioxide of the present invention, the amorphous manganese oxide is in the form of particles. The amorphous manganese oxide preferably has an average particle size of 5 μm or less, more preferably 3 μm or less, still more preferably 1 μm or less, and even more preferably 0.9 μm or less. When the average particle diameter exceeds 5 μm, an operation for preventing amorphous manganese oxide from precipitating during electrolysis, for example, vigorous stirring of the electrolytic solution may be required. When the average particle size is 5 μm or less, amorphous manganese oxide is less likely to settle in the electrolytic solution, and this is easily dispersed uniformly in the electrolytic solution. In order to suppress aggregation of amorphous manganese oxides, the average particle size is preferably 0.5 μm or more.
The amorphous manganese oxide having the above physical properties is obtained, for example, by dissolving a manganese compound in an acidic state and reprecipitating the amorphous manganese oxide, and further dissolving the manganese compound in an acidic solution such as an electrolytic solution, Mention may be made of amorphous manganese oxides obtained by reprecipitation.

In the production method of the present invention, the amorphous manganese oxide concentration in the electrolytic solution is preferably 0.5 mg / L or more, more preferably 0.9 mg / L, and more preferably 4 mg / L or more. More preferably, it is still more preferably 7 mg / L or more. When the concentration of amorphous manganese oxide in the electrolytic solution is 0.5 mg / L or more, the effect of mixing amorphous manganese oxide can be obtained more easily, and more easily pulverized electrolytic manganese dioxide can be obtained. It becomes easy. The concentration of the amorphous manganese oxide in the electrolytic solution does not need to be higher than necessary, and may be 20 mg / L or less, and further 15 mg / L or less.

In the production method of the present invention, it is preferable to mix this in the electrolytic solution so that the amorphous manganese oxide concentration in the electrolytic solution becomes constant. As a result, the physical properties, particularly the pulverization characteristics, of the electrolytic manganese dioxide obtained throughout the electrolysis tend to be uniform.
As a method of mixing amorphous manganese oxide in the electrolytic solution (hereinafter also simply referred to as “mixing method”), that is, as a method of adding amorphous manganese oxide to the electrolytic solution, amorphous manganese oxide is used as the electrolytic solution. A method of directly adding to and mixing with a slurry, a method of adding and mixing a slurry containing amorphous manganese oxide to an electrolytic solution, or a method of mixing an amorphous manganese oxide by generating amorphous manganese oxide in the electrolytic solution Etc. can be illustrated.

As a preferred mixing method, an amorphous manganese oxide can be generated in the electrolytic solution to mix it, and further, amorphous manganese can be obtained by dissolving and re-depositing the manganese compound in the electrolytic solution. The method of mixing this by producing | generating an oxide can be mentioned. Thereby, an electrolytic solution containing amorphous manganese oxide can be obtained. In these cases, the amorphous manganese oxide re-deposited from the manganese compound dissolved in the electrolytic solution becomes suspended particles, which are mixed in the electrolytic solution, and the electrolytic solution becomes an electrolytic solution containing amorphous manganese oxide. .

Examples of preferable manganese compounds to be dissolved in the electrolytic solution include crystalline manganese oxides and manganese oxides obtained by chemical reaction (hereinafter referred to as “chemical manganese oxides”). Compared with electrolytic manganese oxide obtained by an electrochemical reaction such as electrolysis and naturally produced manganese oxide, chemical manganese oxide can efficiently obtain a homogeneous amorphous manganese oxide in an electrolytic solution.

As such a chemical manganese oxide, for example, a crystalline manganese oxide having a manganese oxidation degree of 1 or more and 1.6 or less (x is 1 or more and 1.6 or less when the manganese oxide is represented by MnOx) Furthermore, trimanganese tetroxide (Mn ₃ O ₄ ), manganese trioxide (Mn ₂ O ₃ ), or both can be mentioned. Further, crystalline manganese oxide deposited by oxidizing divalent manganese (Mn ²⁺ ), crystalline trimanganese tetraoxide (Mn ₃ O ₄ ) or three deposited by oxidizing divalent manganese and further precipitated. Manganese dioxide (Mn ₂ O ₃ ) or both can be mentioned. More specifically, manganese oxidation such as trimanganese tetraoxide or manganese trioxide or a mixture thereof obtained by mixing a solution containing divalent manganese and an alkaline solution to oxidize and precipitate divalent manganese. You can list things. The oxidation of divalent manganese may be performed using an oxidizing agent such as air or oxygen.

These chemical manganese oxides are preferably mixed with the electrolytic solution without being subjected to a drying step after the deposition, and the mixed solution containing the chemical manganese oxide after the deposition is more directly mixed into the electrolytic solution as a slurry. preferable. The chemical manganese oxide that has undergone the drying step becomes difficult to dissolve even when mixed in the electrolytic solution. Therefore, even if the chemical manganese oxide obtained through the drying process is mixed with the electrolytic solution, the amorphous manganese oxide does not substantially reprecipitate. Therefore, when the chemical manganese oxide that has been subjected to a drying treatment after precipitation, for example, a treatment for drying the water content to 20% by weight or less, is directly mixed with the electrolyte as a dry powder, or is dispersed in a solvent again to form a slurry. When mixed with an electrolytic solution, amorphous manganese oxide is not substantially formed, and the mixed chemical manganese oxide becomes suspension particles as it is.

In the production method of the present invention, the conditions other than the suspension electrolysis method using amorphous manganese oxide, that is, the production method of electrolyzing an electrolytic solution containing amorphous manganese oxide, are as follows. be able to.

Examples of the electrolytic solution include one or more of a manganese chloride solution, a manganese sulfate solution, and a sulfuric acid-manganese sulfate mixed solution. Among these, the electrolytic solution is preferably a sulfuric acid-manganese sulfate mixed solution. By using the sulfuric acid-manganese sulfate mixed solution as the electrolytic solution, the sulfuric acid concentration becomes constant during the electrolysis period, and the sulfuric acid concentration becomes constant even when electrolysis is performed for a long time. Thereby, it becomes easy to obtain electrolytic manganese dioxide having uniform physical properties.
The electrolytic solution in the present invention is preferably an aqueous solution. Of these, a sulfuric acid-manganese sulfate mixed aqueous solution is particularly preferably used as the electrolytic solution.

In the electrolysis step, it is preferable to perform electrolysis while supplying a replenisher of manganese ions (hereinafter referred to as “supplemental manganese solution”) to the electrolyte. Electrolytic deposition of electrolytic manganese dioxide reduces manganese ions in the electrolyte. In order to make the manganese ion concentration of the electrolytic solution constant during the electrolysis period, the supplemental manganese solution is replenished. In order to efficiently supply manganese ions, the manganese ion concentration of the supplemental manganese solution is preferably 30 g / L or more and 110 g / L or less, and more preferably 30 g / L or more and 60 g / L or less. When a manganese sulfate solution or a sulfuric acid-manganese sulfate mixed solution is used as the electrolytic solution, a manganese sulfate solution is preferably used as the supplemental manganese solution. When a manganese chloride solution is used as the electrolytic solution, a supplemental manganese aqueous solution is used. It is preferable to use a manganese chloride solution as

The electrolyte solution preferably has an acid concentration of 15 g / L or more and 50 g / L or less, more preferably 20 g / L or more and 40 g / L or less, and 20 g / L or more and 30 g / L or less. More preferably. When the acid is sulfuric acid, the acid concentration is the concentration of sulfuric acid (H ₂ SO ₄ ).
The electrolysis step in the production process of the present invention, the electrolysis current density is 0.5A / dm ² or more, further 0.6 A / dm ² or more, and further preferably not 0.8 A / dm ² or more. On the other hand, when the electrolysis current density is 1.8 A / dm ² or less, further 1.5 A / dm ² or less, and further 1.3 A / dm ² or less, an increase in electrolysis voltage during electrosynthesis is suppressed. There is a tendency. Thereby, it becomes easy to produce the electrolytic manganese dioxide of the present invention efficiently and stably.

In order to obtain the electrolytic manganese dioxide of the present invention more stably, the electrolysis current density is preferably 0.6 A / dm ² or more and 1.5 A / dm ² or less, 0.8 A / dm ² or more, and 1. More preferably, it is 5 A / dm ² or less. The electrolysis temperature is preferably 90 ° C. or higher and 98 ° C. or lower, more preferably 95 ° C. or higher and 98 ° C. or lower. The higher the electrolysis temperature, the higher the production efficiency of electrolytic manganese dioxide.

In the production method of the present invention, the step of obtaining electrolytic manganese dioxide by electrolysis may be an electrolysis step, and thereafter, any one or more of a washing step, a pulverization step, and a neutralization step may be included.
In the washing step, the electrolytic manganese dioxide obtained by electrolysis is washed, and the attached electrolytic solution and the like are removed. The washing method includes immersing electrolytic manganese dioxide in a water bath or a warm water bath.
In the neutralization step, the pH of the electrolytic manganese dioxide can be adjusted by immersing the electrolytic manganese dioxide in an aqueous alkali metal solution such as an aqueous sodium hydroxide solution or an aqueous ammonia solution.
In the pulverization step, electrolytic manganese dioxide has an arbitrary particle size. As the pulverization method, any method such as wet pulverization or dry pulverization can be used.

The electrolytic manganese dioxide of the present invention can be used as a raw material for a lithium manganese composite oxide. Thereby, it can be expected to obtain a lithium-manganese composite oxide with few impurities such as iron.

When the electrolytic manganese dioxide of the present invention is a lithium manganese complex oxide, the lithium manganese complex oxide can be obtained by mixing and baking the electrolytic manganese dioxide of the present invention and lithium or a lithium compound.
Any lithium compound may be used, and examples include lithium hydroxide, lithium oxide, lithium carbonate, lithium iodide, lithium nitrate, lithium oxalate, and alkyl lithium. Examples of preferable lithium compounds include lithium hydroxide, lithium oxide, and lithium carbonate.

EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention in detail, this invention is not limited to these Examples.
(Measurement of apparent particle density, particle density and pore distribution)
The apparent particle density, particle density, and pore distribution of the obtained electrolytic manganese dioxide were measured as follows. That is, the agglomerated electrolytic manganese dioxide obtained by electrolysis was coarsely pulverized in an agate mortar to obtain electrolytic manganese dioxide coarse particles having a particle diameter of 1.2 to 2.8 mm. Electrolytic manganese dioxide coarse particles were set in a mercury porosimeter (device name: Pore Sizer 9510, manufactured by Micromeritics), and the pore pressure distribution was measured by gradually changing the mercury pressure range from atmospheric pressure to 414 MPa.
The apparent particle density was obtained from the following equation. That is, the volume obtained by removing the mercury volume (V _Hg ) introduced into the sample at atmospheric pressure from the volume (V _c ) of the measurement container was regarded as the sample volume (V _Mn ). The mass (W _Mn ) of the sample with respect to the sample volume was determined and used as the apparent particle density (ρ _A ).
V _Mn = V _c -V _Hg
ρ _A = W _Mn / V _Mn
Furthermore, the particle density was determined from the following equation. That is, the volume obtained by removing the mercury volume (V _Hg ′) introduced into the sample at a pressure of 414 MPa from the volume (V _c ) of the measurement container was regarded as the sample volume (V _Mn ′). The mass (W _Mn ) of the sample with respect to the sample volume was determined and used as the particle density (ρ _P ).
V _Mn '= V _c -V _Hg '
ρ _P = W _Mn / V _Mn '
Note that the mercury volume introduced into the sample at atmospheric pressure corresponds to the volume formed between the particles. On the other hand, the volume of mercury introduced into the sample at a pressure of 414 MPa corresponds to the total volume between the particles and the pore volume with a pore diameter of 200 nm.

(Calculation of open pores)
Using the apparent particle density (g / mL) and particle density (g / mL) values measured by the mercury porosimeter method, open pores (mL / g) were calculated from the following formula.
Open pores = (1 / apparent particle density-1 / particle density)

(Measurement of BET specific surface area)
The BET specific surface area of the sample was measured by nitrogen adsorption by the BET single point method. As the measuring device, a gas adsorption specific surface area measuring device (device name: Flowsorb III, manufactured by Shimadzu Corporation) was used. Prior to the measurement, the measurement sample was deaerated by heating at 150 ° C. for 60 minutes.

(Measurement of full width at half maximum (FWHM))
The FWHM of electrolytic manganese dioxide was measured using a general X-ray diffractometer (device name: MXP-3, manufactured by Mac Science). A CuKα ray (λ = 1.5405 mm) is used as the radiation source, the measurement mode is step scan, the scan condition is 0.04 ° per second, the measurement time is 3 seconds, and the measurement range is 2 ° to 5 ° to 80 °. Measured with From the result of the obtained powder X-ray diffraction pattern, the full width at half maximum of the diffraction line having 2θ of around 22 ± 1 ° was determined and was defined as FWHM.

(Measurement of crystallinity)
The crystal phase and crystallinity of the manganese oxide in the manganese replenisher and electrolyte were confirmed by powder X-ray diffraction (XRD) measurement of the solid phase obtained by filtering and drying them. The conditions for the XRD measurement were the same as those for the FWHM measurement, and the full width at half maximum of the diffraction peak having the highest diffraction intensity was determined as FWHM.

(Measurement of average particle size)
0.5 g of sample is put into 50 mL of pure water, ultrasonic dispersion is performed for 10 seconds, and a predetermined amount of the dispersed slurry prepared is put into a measuring device (device name: Microtrac HRA, manufactured by HONEWELL), and the particle size distribution by laser diffraction method Was measured. From the obtained particle size distribution data, the particle size distribution, average particle size and maximum particle size were determined. Moreover, the most frequent particle diameter was calculated | required and this was made into the mode particle diameter. In the measurement, the refractive index of pure water was 1.33, and the refractive index of manganese oxide was 2.20. In addition, about the solution samples, such as a manganese oxide slurry, this was directly subjected to ultrasonic irradiation and measurement under the same conditions.

(Measurement of grinding characteristics)
The grinding characteristics of the obtained electrolytic manganese dioxide were measured as follows.
That is, the agglomerated electrolytic manganese dioxide obtained by electrolysis was coarsely pulverized in an agate mortar to obtain electrolytic manganese dioxide coarse particles having a particle diameter of 1.2 to 2.8 mm. 3 g of electrolytic manganese dioxide coarse particles were weighed and pulverized for 15 minutes using an automatic mortar (device name: ANM1000 type, manufactured by Nissho Science). The pulverized electrolytic manganese dioxide powder is sieved with a sieve having an opening of 90 μm, and the weight of electrolytic manganese dioxide particles (electrolytic manganese dioxide particles having a particle diameter of 90 μm or less) that has passed through the sieve with respect to the total weight of the used electrolytic manganese dioxide coarse particles The ratio was calculated.

(Measurement of micro Vickers hardness)
The micro Vickers hardness of electrolytic manganese dioxide was measured as follows. For the measurement, a micro Vickers hardness meter (device name: MVK-E3, manufactured by Akashi Co., Ltd.) was used. As the measurement sample, an electrolytic manganese dioxide block of about 1 cm × 1 cm peeled off from the electrode after electrolytic deposition was used. As a pretreatment, the electrolytic manganese dioxide block was embedded in a resin and cut in a direction parallel to the electrodeposition thickness direction. Then, it was set as the measurement sample by grind | polishing the cut surface of an electrolytic manganese dioxide block. The micro Vickers hardness was measured by driving a diamond indenter into a measurement sample after pretreatment with a weight of 50 kgf. In the measurement, nine regions are defined on the cut surface of the measurement sample so that the area of the analysis section is equally divided into nine parts, and a diamond indenter is driven into each region, and the average of the nine points obtained. The value was taken as the micro Vickers hardness (Hv) of the sample.

(Measurement of particle concentration)
The particle concentration of a solution sample such as an electrolytic solution or a manganese replenishing solution was determined as follows. That is, a certain amount of the sample solution was filtered and solid-liquid separated, and the weight of the obtained solid phase was measured. The weight of the solid phase relative to the volume of the collected sample solution was determined, and the particle concentration was calculated.

Example 1
A manganese sulfate aqueous solution having a manganese concentration of 42 g / L is stirred, and a 1 mol / L sodium hydroxide aqueous solution is added thereto while blowing air into the manganese sulfate aqueous solution containing manganese oxide (hereinafter referred to as “manganese oxide slurry”). .) In addition, these processes were performed at 80 degreeC. The manganese oxide in the obtained manganese oxide slurry was a single phase of trimanganese tetroxide (Mn ₃ O ₄ ). An XRD diagram of the obtained manganese trioxide is shown in FIG. Further, trimanganese tetroxide in the manganese oxide slurry had a particle size distribution that was close to a nodal shape, with a mode particle size of 1.3 μm and a maximum particle size of 26.1 μm.

The obtained manganese oxide slurry was mixed with a separately prepared manganese sulfate aqueous solution to obtain a manganese sulfate aqueous solution containing 25 mg / L of Mn ₃ O _{4 and} having a manganese concentration of 42 g / L, and this was supplied as a manganese replenisher solution. It was.
Further, a sulfuric acid-manganese sulfate aqueous solution having a sulfuric acid concentration of 25 g / L was used as the electrolytic solution.
Electrolytic manganese dioxide was produced by electrolyzing the manganese replenisher while continuously replenishing the electrolyte during the electrolysis period so that the sulfuric acid concentration of the electrolyte during the electrolysis period was constant. The electrolysis current density during electrolysis was 1.5 A / dm ² , and the electrolysis temperature was 96 ° C.

It was confirmed that by adding a manganese replenisher containing Mn ₃ O ₄ to the electrolyte, Mn ₃ O ₄ was dissolved in the electrolyte and amorphous manganese oxide was generated (re-deposited). The amorphous manganese oxide concentration in the electrolytic solution was 6.9 mg / L. The physical property evaluation results of the amorphous manganese oxide in the electrolytic solution are shown in Table 1, and the XRD diagram is shown in FIG.

The obtained electrolytic manganese dioxide has an apparent particle density of 4.0 g / cm ³ (= 4.0 g / mL) and a particle density of 4.3 g / cm ³ (= 4.3 g / mL). Was showing.
The production conditions for electrolytic manganese dioxide are shown in Table 2, and the physical property evaluation results of the produced electrolytic manganese dioxide are shown in Table 3.

Example 2
Electrolytic manganese dioxide was produced in the same manner as in Example 1 except that the Mn ₃ O ₄ concentration in the manganese replenisher was 200 mg / L.
It was confirmed that amorphous manganese oxide was generated in this example, and the concentration of amorphous manganese oxide in the electrolytic solution was 13 mg / L.

The production conditions are shown in Table 2, and the physical property evaluation results of the produced electrolytic manganese dioxide are shown in Table 3. Further, the pore size distribution of the produced electrolytic manganese dioxide is shown in FIG. As is apparent from FIG. 3, the pore volume of the electrolytic manganese dioxide of this example exceeding the pore diameter of 0.2 μm exceeded 0.03 mL / g. Thereby, in the electrolytic manganese dioxide in a present Example, it has confirmed that the pore whose pore diameter exceeds 0.2 micrometer exists as an open pore.
Furthermore, the result of SEM observation of the manufactured electrolytic manganese dioxide is shown in FIG. From FIG. 4, it was confirmed that the electrolytic manganese dioxide had fine crystals having a substantially mesh shape, and thus had open pores having an irregular shape of 0.2 μm or more.

Example 3
Electrolytic manganese dioxide was produced in the same manner as in Example 1 except that the Mn ₃ O ₄ concentration in the manganese replenisher was 100 mg / L.
It was confirmed that amorphous manganese oxide was generated in this example, and the concentration of amorphous manganese oxide in the electrolytic solution was 9.4 mg / L.
The production conditions are shown in Table 2, and the physical property evaluation results of the produced electrolytic manganese dioxide are shown in Table 3. Furthermore, by SEM observation, it was confirmed that the electrolytic manganese dioxide has fine crystals having a substantially mesh shape, and thereby has open pores having an irregular shape with an approximate diameter of the pores of 0.2 μm or more. .

Example 4
Electrolytic manganese dioxide was produced in the same manner as in Example 1 except that the Mn ₃ O ₄ concentration in the manganese replenisher was 50 mg / L.
In this example, it was confirmed that the same amorphous manganese oxide as in Example 1 was formed, and the concentration of amorphous manganese oxide in the electrolytic solution was 7.5 mg / L.
The production conditions are shown in Table 2, and the physical property evaluation results of the produced electrolytic manganese dioxide are shown in Table 3.

Example 5
An aqueous manganese sulfate solution having a manganese concentration of 42 g / L was stirred, and 3 mol / L sodium hydroxide aqueous solution was added thereto while blowing air to obtain a manganese oxide slurry. After adding the aqueous sodium hydroxide solution, this was stirred for 1 hour while blowing air into the obtained manganese oxide slurry. In addition, these processes were performed at the temperature of 60 degreeC. After stirring, the manganese oxide in the obtained manganese oxide slurry was a single phase of trimanganese tetraoxide (Mn ₃ O ₄ ) similar to that in Example 1.

The manganese oxide slurry and a separately prepared manganese sulfate aqueous solution were mixed to obtain a manganese sulfate aqueous solution containing 15 mg / L of Mn ₃ O _{4 and} having a manganese concentration of 42 g / L, which was used as a manganese replenisher. .
Electrolytic manganese dioxide was produced in the same manner as in Example 1 except that the manganese replenisher was used and that the electrolytic current density was 0.88 A / dm ² .
In this example, it was confirmed that the same amorphous manganese oxide as in Example 1 was generated. Moreover, the density | concentration of the amorphous manganese oxide in electrolyte solution was 0.9 mg / L. Table 1 shows the physical property evaluation results of the amorphous manganese oxide.
The production conditions are shown in Table 2, and the physical property evaluation results of the produced electrolytic manganese dioxide are shown in Table 3.

Example 6
An aqueous manganese sulfate solution having a manganese concentration of 42 g / L was stirred, and 3 mol / L sodium hydroxide aqueous solution was added thereto while blowing air to obtain a manganese oxide slurry. After adding the aqueous sodium hydroxide solution, this was stirred for 1 hour while blowing air into the obtained manganese oxide slurry. These treatments were performed at a temperature of 80 ° C. After stirring, the manganese oxide in the obtained manganese oxide slurry was a single phase of trimanganese tetraoxide (Mn ₃ O ₄ ). Further, the trimanganese tetraoxide in the manganese oxide slurry had a particle size distribution close to a nodal shape, the mode particle size was 8.48 μm and the maximum particle size was 62.2 μm.

By mixing the manganese oxide slurry and a separately prepared manganese sulfate aqueous solution, a manganese sulfate aqueous solution containing 50 mg / L of Mn ₃ O _{4 and} having a manganese concentration of 42 g / L was obtained. The obtained manganese sulfate aqueous solution was used as a manganese replenisher.
Electrolytic manganese dioxide was produced in the same manner as in Example 1 except that the manganese replenisher was used.
In this example, an amorphous manganese oxide similar to that in Example 1 was produced, but the average particle size was larger than that in Example 1. Moreover, the density | concentration of the amorphous manganese oxide in electrolyte solution was 7.5 mg / L. Table 1 shows the physical property evaluation results of the amorphous manganese oxide.
The production conditions are shown in Table 2, and the physical property evaluation results of the produced electrolytic manganese dioxide are shown in Table 3.

Example 7
A manganese oxide slurry was obtained in the same manner as in Example 5 except that the manganese oxide slurry after addition of the aqueous sodium hydroxide solution was not stirred. The manganese oxide in the obtained manganese oxide slurry was a single phase of trimanganese tetroxide (Mn ₃ O ₄ ). Further, the trimanganese tetraoxide in the manganese oxide slurry had a shape with a particle size distribution close to nodal, the mode particle size was 1.26 μm, and the maximum particle size was 37.0 μm.

By mixing the manganese oxide slurry and a separately prepared manganese sulfate aqueous solution, a manganese sulfate aqueous solution containing 50 mg / L of Mn ₃ O _{4 and} having a manganese concentration of 42 g / L was obtained. The obtained manganese sulfate aqueous solution was used as a manganese replenisher.
Electrolytic manganese dioxide was produced in the same manner as in Example 1 except that the manganese replenisher was used.

In this example, an amorphous manganese oxide similar to that in Example 1 was produced, but the average particle size was larger than that in Example 1. The concentration of amorphous manganese oxide in the electrolytic solution was 4.4 mg / L. Table 1 shows the physical property evaluation results of the amorphous manganese oxide.
The production conditions are shown in Table 2, and the physical property evaluation results of the produced electrolytic manganese dioxide are shown in Table 3.

Example 8
A manganese oxide slurry was obtained in the same manner as in Example 1 except that an aqueous manganese sulfate solution having a manganese concentration of 40 g / L was used. The obtained manganese oxide was a single phase of trimanganese tetraoxide (Mn ₃ O ₄ ). Further, the trimanganese tetraoxide in the manganese oxide slurry has a shape in which the particle size distribution is distributed over a wide particle size range, and the mode particle size is 23.9 μm, but the frequency of the particle size of 1.26 μm. Was similar to this. The maximum particle size was 104.7 μm.

By mixing the obtained manganese oxide slurry with a separately prepared manganese sulfate aqueous solution, a manganese sulfate aqueous solution containing 60 g / L of Mn ₃ O ₄ and manganese oxide having a manganese concentration of 40 g / L is obtained. This was used as a manganese replenisher.
Further, a manganese sulfate aqueous solution having a manganese concentration of 40 g / L was separately prepared and used as an auxiliary manganese replenisher.
A sulfuric acid-manganese sulfate aqueous solution having a sulfuric acid concentration of 25 g / L was used as the electrolytic solution. Electrolytic manganese dioxide was produced by performing electrolysis while supplying the manganese replenisher and the auxiliary manganese replenisher simultaneously and continuously to the electrolyte so that the sulfuric acid concentration of the electrolyte during the electrolysis was constant.

The flow rate ratio of the manganese replenisher and auxiliary manganese replenisher supplied to the electrolyte was manganese replenisher: auxiliary manganese replenisher = 1: 3. The electrolytic current density was 1.3 A / dm ² and the electrolysis temperature was 96 ° C.
During the electrolysis period, it was confirmed that trimanganese tetraoxide was dissolved in the electrolytic solution and suspended particles were generated, and the concentration of the suspended particles in the electrolytic solution was 3.0 mg / L. The results of the physical property evaluation of the suspended particles are shown in Table 1. The generated suspended particles were amorphous manganese oxide.
The production conditions are shown in Table 4, and the physical property evaluation results of the produced electrolytic manganese dioxide are shown in Table 5.

Example 9
The manganese oxide slurry obtained by the same method as in Example 8 is mixed with a separately prepared aqueous manganese sulfate solution, thereby containing 200 mg / L of Mn ₃ O ₄ and a manganese oxide having a manganese concentration of 40 g / L. An aqueous manganese sulfate solution was obtained, which was used as a manganese replenisher.
Electrolytic manganese dioxide was produced in the same manner as in Example 8 except that the manganese replenisher was used.
During the electrolysis period, it was confirmed that trimanganese tetraoxide was dissolved in the electrolytic solution and suspended particles were generated, and the concentration of the suspended particles in the electrolytic solution was 8.3 mg / L. The produced suspended particles were the same amorphous manganese oxide as in Example 8.
The production conditions are shown in Table 4, and the physical property evaluation results of the produced electrolytic manganese dioxide are shown in Table 5.

Example 10
The manganese oxide slurry obtained by the same method as in Example 8 was mixed with a separately prepared manganese sulfate aqueous solution, so that manganese oxide containing 240 mg / L of Mn ₃ O _{4 and} having a manganese concentration of 40 g / L was used. An aqueous manganese sulfate solution was obtained, which was used as a manganese replenisher.
The manganese replenisher was used, the flow rate ratio of the manganese replenisher and auxiliary manganese replenisher supplied to the electrolyte was set to manganese replenisher: auxiliary manganese replenisher = 1: 4, and the electrolysis current density was set to 0. Electrolytic manganese dioxide was produced in the same manner as in Example 8 except that 88 A / dm ² was used.

During the electrolysis period, it was confirmed that trimanganese tetraoxide was dissolved in the electrolytic solution and suspended particles were generated, and the concentration of the suspended particles in the electrolytic solution was 4.6 mg / L. The produced suspended particles were the same amorphous manganese oxide as in Example 8.
The production conditions are shown in Table 4, and the physical property evaluation results of the produced electrolytic manganese dioxide are shown in Table 5.

Comparative Example 1
A conventional easily pulverized electrolytic manganese dioxide was produced by the following method.
A sulfuric acid-manganese sulfate aqueous solution having a sulfuric acid concentration of 25 g / L was used as the electrolytic solution. Further, an aqueous manganese sulfate solution not containing Mn ₃ O ₄ was used as a manganese replenisher, and electrolysis was performed while continuously replenishing the electrolyte during the electrolysis period to produce manganese dioxide. The electrolysis current density during electrolysis was 0.8 A / dm ² , and the electrolysis temperature was 92 ° C. The production conditions are shown in Table 6, and the physical property evaluation results of the produced electrolytic manganese dioxide are shown in Table 7.

The obtained electrolytic manganese dioxide had a BET specific surface area as high as 50 m ² / g. However, the particle density was 3.9 g / mL. Thus, it has been confirmed that electrolytic manganese dioxide produced by an electrolytic method that does not use manganese oxide, that is, a so-called clarified electrolytic method, has a lower filling property than the electrolytic manganese dioxide of the present invention.

Comparative Example 2
A conventional electrolytic manganese dioxide having a high filling property was produced by the following method.
A sulfuric acid-manganese sulfate aqueous solution having a sulfuric acid concentration of 34 g / L was used as the electrolytic solution. Further, an aqueous manganese sulfate solution containing no Mn ₃ O ₄ was used as a manganese replenisher, and electrolysis was performed while replenishing the electrolyte continuously during the electrolysis period to produce manganese dioxide. The electrolysis current density during electrolysis was 0.6 A / dm ² , and the electrolysis temperature was 96 ° C. The production conditions are shown in Table 6, and the physical property evaluation results of the produced electrolytic manganese dioxide are shown in Table 7.

The electrolytic manganese dioxide of the comparative example had a BET specific surface area as low as 20 m ² / g and an apparent particle density of 3.9 g / mL, indicating a higher packing property than the electrified manganese dioxide of comparative example 1.
Furthermore, the result of the SEM observation of the comparative example is shown in FIG. The microstructure of the electrolytic manganese dioxide was uniform and dense, and a substantially mesh-like microstructure like the electrolytic manganese dioxide of the present invention could not be confirmed.

Comparative Example 3
Electrolytic manganese dioxide was produced by a suspension electrolysis method. A sulfuric acid-manganese sulfate aqueous solution having a sulfuric acid concentration of 25 g / L was used as the electrolytic solution, and an aqueous manganese sulfate solution containing 50 mg / L of electrolytic manganese dioxide particles having an average particle size of 0.63 μm was used as a manganese replenisher for continuous electrolysis during the electrolysis period. The solution was replenished and electrolysis was carried out at a current density of 1.5 A / dm ² and an electrolysis temperature of 96 ° C. to produce electrolytic manganese dioxide. The production conditions are shown in Table 6, and the physical property evaluation results of the produced electrolytic manganese dioxide are shown in Table 7. Moreover, the pore distribution of the produced electrolytic manganese dioxide is shown in FIG.

In the comparative example, amorphous manganese oxide was not generated in the electrolytic solution. Moreover, the result of SEM observation of the produced electrolytic manganese dioxide is shown in FIG. From FIG. 6, it was confirmed that the electrolytic manganese dioxide had a fine structure in which coarse secondary particles of about 100 μm were aggregated. In addition, the electrolytic manganese dioxide had many open pores, and the apparent particle density was lower than that in Examples.

Comparative Example 4
Electrolytic manganese dioxide was produced under the same conditions as in Example 1 except that none of the manganese oxides were used (the manganese oxide particle concentration was adjusted to 0 mg / L).
In the comparative example, the electrolysis voltage increased to 3.20 V during the electrolysis period, and as a result, the electrolytic manganese dioxide electrodeposited on the electrode dropped off from the electrode, and the electrolytic manganese dioxide could not be obtained. The production conditions of Comparative Example 3 are shown in Table 6.

Comparative Example 5
Manganese oxide slurry was obtained in the same manner as in Example 1. Next, the manganese oxide slurry was filtered, and the obtained solid phase was dried at 110 ° C. overnight to obtain manganese oxide. The obtained manganese oxide was a single phase of trimanganese tetraoxide (Mn ₃ O ₄ ) and had a powder X-ray diffraction pattern equivalent to that of trimanganese tetraoxide of Example 1. The water content of the trimanganese tetraoxide was 20% or less.

By dispersing the dried trimanganese tetraoxide in an aqueous manganese sulfate solution having a manganese concentration of 42 g / L, a manganese oxide slurry containing 100 mg / L of the trimanganese tetraoxide and having a manganese concentration of 42 g / L was obtained. A manganese replenisher was used.
Electrolytic manganese dioxide was produced in the same manner as in Example 1 except that the manganese replenisher was used. The suspended particle concentration in the electrolytic solution was 9.4 mg / L.
In this comparative example, trimanganese tetraoxide in the manganese replenisher remained as it was and became suspended particles. In addition, amorphous manganese oxide was not generated in the electrolytic solution. FIG. 7 shows a powder X-ray diffraction pattern of trimanganese tetraoxide in the manganese replenisher in this comparative example, and FIG. 8 shows a powder X-ray diffraction pattern of suspended particles in the electrolyte.
The production conditions are shown in Table 6, and the physical property evaluation results of the produced electrolytic manganese dioxide are shown in Table 7.

Comparative Example 6
An aqueous manganese sulfate solution containing 25 mg / L of electrolytic manganese dioxide particles having an average particle size of 0.63 μm and a manganese concentration of 40 g / L was used as a manganese replenisher, and the electrolytic current density was 0.88 A / dm ² . Except for this, electrolytic manganese dioxide was produced in the same manner as in Example 1. The suspended particles in the electrolyte were the same electrolytic manganese dioxide as the manganese replenisher, and the particle concentration in the electrolyte was 4.6 mg / L.
The production conditions are shown in Table 6, and the physical property evaluation results of the produced electrolytic manganese dioxide are shown in Table 7.

(Evaluation of grinding characteristics)
The grinding characteristics of the electrolytic manganese dioxide produced in Examples and Comparative Examples 1, 2, 5 and 6 were evaluated. The results are shown in Table 8. As a result, the electrolytic manganese dioxide of the example has a particle ratio of 90 μm or less (hereinafter simply referred to as “particle ratio”) after pulverization for 15 minutes and easily pulverizes in a short time. Has been demonstrated. In contrast, the electrolytic manganese dioxide of Comparative Example 2 had a particle ratio of only 39% by weight, and only about half of the electrolytic manganese dioxide of the present invention was pulverized.

Furthermore, the experimental conditions are the same as in Example 3 except that the drying treatment is performed on trimanganese tetraoxide. However, the particle ratio of electrolytic manganese dioxide of Example 3 is 75% by weight, whereas the particle ratio of electrolytic manganese dioxide of Comparative Example 5 is 65% by weight, and Example 3 is 10% more than Comparative Example 5. The percentage of particles was higher than%.
Thereby, it was confirmed that the electrolytic manganese dioxide of the present invention was excellent in grinding characteristics. Moreover, although the electrolytic manganese dioxide of the comparative example 1 had a high grinding | pulverization characteristic, the filling property was low. From these results, it was confirmed that the electrolytic manganese dioxide of the present invention is an electrolytic manganese dioxide excellent not only in filling properties but also in grinding characteristics.

(Evaluation of micro Vickers hardness)
The micro Vickers hardness of the electrolytic manganese dioxide obtained in Examples 8, 9, and 10 and Comparative Examples 1, 2, and 6 was measured. The results are shown in Table 9.

The micro Vickers hardness of any of the examples also had an Hv of 400 or less, whereas all of the comparative examples had an Hv of over 400. From this, it was found that the electrolytic manganese dioxide of the example was easily pulverized and had low hardness.
Further, the electrolytic manganese dioxide of Example 8 and Comparative Example 1 each had a particle ratio of 87% by weight. Nevertheless, the electrolytic manganese dioxide of Example 8 had a lower micro Vickers hardness than the electrolytic manganese dioxide of Comparative Example 1. From this, the grindability of the conventional easily grindable electrolytic manganese dioxide (Comparative Example 1) is derived from its high specific surface area, whereas the grindability of the electrolytic manganese dioxide of the present invention is that of electrolytic manganese dioxide. It was confirmed that it originated from its own hardness.

The electrolytic manganese dioxide of the present invention is suitably used as a positive electrode active material for a primary battery such as an alkaline battery or as a raw material for a lithium manganese composite oxide that is a positive electrode active material for a lithium ion secondary battery.

The entire contents of the specification, claims, drawings, and abstract of Japanese Patent Application No. 2012-022065 filed on February 3, 2012 are cited herein as disclosure of the specification of the present invention. Incorporated.

Claims (15)

1. An electrolytic manganese dioxide having an apparent particle density of 3.0 g / cm ³ or more and a particle density of 4.25 g / cm ³ or more.
2. 2. The electrolytic manganese dioxide according to claim 1, wherein the open pores are 0.01 mL / g or more.
3. BET specific surface area of ^{10 m} 2 / g or more, electrolytic manganese dioxide according to claim 1 or 2, characterized in that at most ^{45 m} 2 / g.
4. The method for producing electrolytic manganese dioxide according to any one of claims 1 to 3, wherein amorphous manganese oxide is mixed in the electrolytic solution.
5. The method for producing electrolytic manganese dioxide according to claim 4, wherein amorphous manganese oxide is produced in the electrolytic solution, and the amorphous manganese oxide is mixed in the electrolytic solution.
6. The method for producing electrolytic manganese dioxide according to claim 4 or 5, wherein amorphous manganese oxide is mixed into the electrolytic solution by dissolution and reprecipitation of the manganese compound in the electrolytic solution.
7. The method for producing electrolytic manganese dioxide according to claim 6, wherein the manganese compound is a crystalline manganese oxide.
8. The method for producing electrolytic manganese dioxide according to claim 6 or 7, wherein the manganese compound is a crystalline manganese oxide having a manganese oxidation degree of 1 or more and 1.6 or less.
9. The method for producing electrolytic manganese dioxide according to any one of claims 6 to 8, wherein the manganese compound is a chemical manganese oxide.
10. The method for producing electrolytic manganese dioxide according to any one of claims 6 to 9, wherein the manganese compound is trimanganese tetraoxide or manganese trioxide or both.
11. The method for producing electrolytic manganese dioxide according to any one of claims 4 to 10, wherein the concentration of amorphous manganese oxide in the electrolytic solution is 0.5 mg / L or more and 20 mg / L or less.
12. The method for producing electrolytic manganese dioxide according to any one of claims 4 to 11, wherein the amorphous manganese oxide has a BET specific surface area of 80 m ² / g or more.
13. The method for producing electrolytic manganese dioxide according to any one of claims 4 to 12, wherein the electrolytic solution is a mixed solution of sulfuric acid and manganese sulfate.
14. The electrolytic manganese dioxide production method according to any one of claims 4 to 13, wherein an electrolytic current density is 0.5 A / dm ² or more and 1.5 A / dm ² or less.
15. A lithium manganese based composite oxide obtained by using the electrolytic manganese dioxide according to any one of claims 1 to 3.

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