WO2018180208A1

WO2018180208A1 - Electrolytic manganese dioxide, method for manufacturing same, and application for same

Info

Publication number: WO2018180208A1
Application number: PCT/JP2018/008106
Authority: WO
Inventors: 鈴木直人; 井手望水; 末次和正
Original assignee: 東ソー株式会社
Priority date: 2017-03-27
Filing date: 2018-03-02
Publication date: 2018-10-04
Also published as: JP7063007B2; JP2019081686A

Abstract

Provided is electrolytic manganese dioxide with high-rate discharge characteristics when used as a positive electrode in an alkaline manganese dry cell. The electrolytic manganese dioxide has a micro hole surface area of 45 – 90 m²/g and a twin crystal proportion of 40 – 80% in the crystal structure. Also provided are a method for manufacturing the electrolytic manganese dioxide and an application thereof.

Description

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

The present invention relates to electrolytic manganese dioxide, a method for producing the same, and uses thereof. More specifically, the present invention relates to electrolytic manganese dioxide used as a positive electrode active material in, for example, a manganese dry battery, particularly an alkaline manganese dry battery, and a method for producing the same.

Manganese dioxide is known, for example, as a positive electrode active material for manganese dry batteries, particularly alkaline manganese dry batteries, and has the advantage of being excellent in storage stability and being inexpensive. In particular, alkaline manganese batteries using manganese dioxide as the positive electrode active material have excellent characteristics in a wide range of discharge rates from low-rate discharge to high-rate discharge, so they are widely used in electronic cameras, portable information devices, game machines and toys. in use.

However, the alkaline manganese battery has a problem that the practical discharge capacity is greatly impaired because the utilization rate of manganese dioxide, which is a positive electrode active material, decreases as the discharge current increases and cannot be used in a state where the discharge voltage is reduced. was there. In other words, when an alkaline manganese battery is used in a device that uses a large current (high rate discharge), the charged positive electrode active material manganese dioxide is not fully utilized, and the usable time is short. It was.

Up to now, in order to improve the high-rate discharge characteristics, the half width of the (110) plane in the XRD measurement using CuKα rays as the light source is 2.2 ° to 2.9 °, and the X-ray diffraction peak (110) / (021) Manganese dioxide characterized in that the peak intensity ratio is 0.50 or more and 0.80 or less has been proposed (Patent Document 1).

Also proposed is an electrolytic manganese dioxide characterized in that the peak intensity ratio is 0.50 <I (110) / I (021) <0.70 and I (221) / I (021) <0.70. (Patent Document 2).

Furthermore, the use of manganese dioxide having a half width of the (110) plane measured by powder X-ray diffraction measurement in the range of 2.00 ° to 2.40 ° has been proposed (Patent Document 3).

However, even manganese dioxide having the above characteristics is not sufficient to solve the problems in high-rate discharge, and excellent manganese dioxide that can exhibit high capacity and long life under high-rate discharge conditions in which a large current is taken out in a short time, so-called high-rate Manganese dioxide having better discharge characteristics has been desired.

Japanese Unexamined Patent Publication No. 2009-135067 Japanese Laid-Open Patent Publication No. 2007-141643 International Publication 2013/157181

An object of the present invention is an electrolytic manganese dioxide used as a positive electrode active material of a manganese dry battery, particularly an alkaline manganese dry battery excellent in high-rate discharge characteristics, which has a different micropore surface area from the conventional one and has a crystal of electrolytic manganese dioxide. The present invention provides electrolytic manganese dioxide having a small twin rate in the structure, a method for producing the same, and use thereof.

As a result of intensive studies on electrolytic manganese dioxide used as a positive electrode active material for manganese dry batteries, particularly alkaline manganese dry batteries, the present inventors have a micropore area of 45 m ² / g or more and 90 m ² / g or less, and In order to complete the present invention, it has been found that the twin rate in the crystal structure is 40% or more and 80% or less, so that the cathode material has excellent high rate discharge characteristics and high filling properties. It came.

That is, the present invention resides in the following [1] to [10].

[1] An electrolytic manganese dioxide having a micropore area of 45 m ² / g or more and 90 m ² / g or less and a twin rate in a crystal structure of 40% or more and 80% or less.

[2] The electrolytic manganese dioxide as described in [1] above, wherein the alkali potential is 250 mV or more and 310 mV or less.

[3] The electrolytic manganese dioxide as described in [1] or [2] above, wherein the content of sulfate radical (SO ₄ ) is 1.5% by weight or less.

[4] The electrolytic manganese dioxide as described in any one of [1] to [3] above, wherein the sodium content is 10 ppm by weight or more and 5,000 ppm by weight or less.

[5] The value of (B) / (A) is 0.90 for the mode particle size (A) in the volume frequency distribution and the particle size width (B) that is 1/2 the mode particle size (A). The electrolytic manganese dioxide according to any one of [1] to [4] above, which is 2.0 or more and 2.0 or less.

[6] The electrolytic manganese dioxide as described in any one of [1] to [5] above, wherein the average particle size is 20 μm or more and 50 μm or less.

[7] with manganese ion concentration in the replenishment manganese liquid supplied to the electrolytic cell is 40 g / L or more, the electrolytic current density is 0.1 A / dm ² or more 1.0A / dm ² or less, the electrolytic solution at the time of initiation of the electrolysis The method for producing electrolytic manganese dioxide according to any one of the above [1] to [6], wherein the sulfuric acid concentration in the solution is 44 g / L or more and 50 g / L or less and the number of days of electrolysis is 15 days or less .

[8] Use a sulfuric acid-manganese sulfate mixed solution whose sulfuric acid concentration in the electrolytic solution at the end of electrolysis is higher than the sulfuric acid concentration in the electrolytic solution at the start of electrolysis, and sulfuric acid concentration in the electrolytic solution at the end of electrolysis Is 32 g / L or more and 80 g / L or less, The manufacturing method of the electrolytic manganese dioxide as described in said [7] characterized by the above-mentioned.

[9] A positive electrode active material for a battery comprising the electrolytic manganese dioxide according to any one of [1] to [6] above.

[10] A battery comprising the battery positive electrode active material according to [9].

The electrolytic manganese dioxide of the present invention is excellent in high-rate discharge characteristics and filling properties when used as a positive electrode material for alkaline dry batteries, and the electrolytic manganese dioxide of the present invention can be obtained by the production method of the present invention.

Hereinafter, the present invention will be described in more detail.

The electrolytic manganese dioxide of the present invention has a micropore area of 45 m ² / g or more and 90 m ² / g or less. When the micropore area is smaller than 45 m ² / g, the voltage drop when the electrolytic manganese dioxide is discharged becomes large, and as a result, the high rate characteristic tends to be lowered, which is not preferable. When the micropore area is larger than 90 m ² / g, the powder density of the electrolytic manganese dioxide is lowered, and the filling property to the dry battery is lowered, which is not preferable. The micropore area is preferably 45 m ² / g or more and 70 m ² / g or less.

Usually, a voltage drop occurs when an alkaline manganese battery is pulse-discharged at a high rate. There are two types of voltage drops, one with a response speed as fast as several tens of milliseconds (hereinafter referred to as voltage drop 1) and one with a response speed slower than several tens of milliseconds (hereinafter referred to as voltage drop 2). . When the voltage drop is large, the utilization factor of the active material is lowered. Therefore, in order to increase the utilization factor, it is desirable that the voltage drop (the sum of the voltage drop 1 and the voltage drop 2) is small. By reducing the voltage drop, the utilization factor of the active material can be increased, and as a result, the high rate discharge performance of the alkaline manganese battery can be improved.

On the other hand, the discharge formula of electrolytic manganese dioxide is usually represented by the following formula.

MnO ₂ + H ₂ O + e ⁻ → MnOOH + OH ⁻
At this time, first, a charge transfer reaction for taking in [H ⁺ ] from H ₂ O in the electrolytic solution occurs on the surface of the electrolytic manganese dioxide. The resistance to the charge transfer reaction (charge transfer resistance) is closely related to the magnitude of the voltage drop (voltage drop 1) having a fast response speed, and it is estimated that the voltage drop 1 becomes small when the charge transfer resistance is small.

On the other hand, since the charge transfer reaction occurs on the surface of the electrolytic manganese dioxide, if the surface area of the electrolytic manganese dioxide is large, the reaction is likely to proceed and the charge transfer resistance is reduced. Electrolytic manganese dioxide has pores of 2 nm or less (hereinafter referred to as micropores) and pores of 2 to 50 nm (hereinafter referred to as mesopores), but the surface area of the micropores is 3 to 5 in comparison with mesopores. Since it is about twice as large, the charge transfer reaction is presumed to occur mainly on the surface of the micropores.

Therefore, if the micropore area of electrolytic manganese dioxide is large, the charge transfer resistance is small, so the voltage drop 1 is also small. As a result, it is presumed that the high-rate characteristics of the alkaline manganese battery are likely to be improved.

The electrolytic manganese dioxide of the present invention has a twin rate in the crystal structure of 40% or more and 80% or less. If the twin rate is less than 40%, the voltage when the alkaline manganese battery is made is low, which is not preferable. If the twin rate is greater than 80%, the voltage drop 2 becomes large, and the high rate characteristics of the alkaline manganese dry battery are likely to deteriorate, which is not preferable. The twin rate in the crystal structure is preferably 40% or more and 70% or less, and more preferably 50% or more and 70% or less.

At the time of discharge of electrolytic manganese dioxide, after a charge transfer reaction that takes in [H ⁺ ] from H ₂ O in the electrolytic solution on the surface of electrolytic manganese dioxide, [H ⁺ ] diffuses in the crystal structure of electrolytic manganese dioxide. MnO ₂ reacts with [H ⁺ ] to produce MnOOH. The diffusion rate of [H ⁺ ] in the crystal structure is closely related to the voltage drop 2 observed during the discharge of electrolytic manganese dioxide, and it is estimated that the voltage drop 2 becomes small when the diffusion rate is high.

On the other hand, electrolytic manganese dioxide is γ-type MnO ₂ , and it is known that twins exist in the crystal structure. When [H ⁺ ] diffuses in the crystal structure of electrolytic manganese dioxide, if there are few twins, the diffusion becomes smooth because the diffusion becomes smooth, and as a result, the voltage drop 2 is estimated to be small.

Therefore, when the twin rate in the crystal structure of electrolytic manganese dioxide is small, the voltage drop 2 is small, and as a result, it is presumed that the high rate characteristics of the alkaline manganese dry battery are likely to be improved.

The electrolytic manganese dioxide of the present invention maintains high voltage and storage characteristics when it is used as an alkaline manganese battery, and can increase the discharge time until the lower limit of usable discharge voltage. Therefore, the alkaline potential may be 250 mV or more and 310 mV or less. preferable. The alkali potential is more preferably 280 mV to 310 mV, and still more preferably 290 mV to 310 mV. The alkali potential is measured in a 40 wt% KOH aqueous solution with a mercury / mercury oxide reference electrode as a standard.

In the electrolytic manganese dioxide of the present invention, the voltage drop 1 becomes small, and when the alkaline manganese battery is made, the high-rate characteristic is more excellent, and the storage characteristic of the dry battery is kept high, so that the content of sulfate radical (SO ₄ ) is 1. It is preferably 5% by weight or less, and more preferably 1.3% by weight or less.

The electrolytic manganese dioxide of the present invention has a low corrosiveness to a metal material such as a can when it is an alkaline manganese dry battery, and the voltage drop 1 is small, so that the high rate characteristics when the alkaline manganese dry battery is made can be maintained. It is preferable that sodium content is 10 weight ppm or more and 5,000 weight ppm or less, More preferably, it is 10 weight ppm or more and 3,000 weight ppm or less. Since sodium contained in electrolytic manganese dioxide is mainly derived from sodium hydroxide used as a neutralizing agent, most of it is adsorbed on the particle surface.

The electrolytic manganese dioxide of the present invention has a mode particle size (A) in the volume frequency distribution and a particle size width (B) that is 1/2 height of the mode particle size (A). The value is preferably 0.90 or more and 2.0 or less. The mode particle size (A) in the volume frequency distribution refers to the particle size having the largest volume frequency in the distribution, and the particle size width (B) that is ½ the mode particle size (A) is the maximum. The spread of the particle diameter from the minimum value to the maximum value of the particle diameter at half the height of the frequent particle diameter (A). It is preferably 0.90 or more and 1.7 or less, more preferably 1.1 or more and 1.6 or less.

¡Pressure density of electrolytic manganese dioxide increases when the particle size composition satisfies the above characteristics. When electrolytic manganese dioxide is used as the positive electrode of a dry battery, it is mixed with a conductive agent such as graphite and used as a molded body. However, the contact density between electrolytic manganese dioxide and conductive agent is improved by increasing the press density of electrolytic manganese dioxide. In addition, the powder resistance of the positive electrode is reduced, and as a result, the high rate characteristics of the dry battery are improved.

The particle size composition of the electrolytic manganese dioxide of the present invention is represented by a volume frequency distribution. The mode particle size (A) is not particularly limited as long as the value of (B) / (A) is 0.90 or more and 2.0 or less, but is preferably 20 μm or more from the pulverization efficiency. 75 μm or less is preferable from the viewpoint of reactivity. Further, the particle size width (B) that is 1/2 height of the mode particle size (A) is particularly limited as long as the value of (B) / (A) is 0.90 or more and 2.0 or less. However, it is preferably 15 μm or more and 80 μm or less from the viewpoint of productivity.

The electrolytic manganese dioxide of the present invention has a small voltage drop 2 when an alkaline manganese battery is formed, and it is easy to improve the high-rate characteristics. Therefore, the half width of the (110) plane by the XRD measurement using CuKα rays as the light source is 1. The angle is preferably from 8 ° to 2.2 °, more preferably from 1.8 ° to 2.1 °.

The electrolytic manganese dioxide of the present invention has a BET specific surface area of preferably 10 m ² / g or more and 40 m ² / g or less because the voltage drop 1 when an alkaline manganese dry battery is formed becomes small and the high rate characteristics are easily improved. 25 m ² / g or more and 35 m ² / g or less is more preferable.

The electrolytic manganese dioxide of the present invention makes it easy to achieve both battery performance and filling density when an alkaline dry battery is used, so that the average particle diameter is preferably 20 μm or more and 50 μm or less, and more preferably 20 μm or more and 40 μm or less. .

Next, the method for producing electrolytic manganese dioxide of the present invention will be described.

In the method for producing electrolytic manganese dioxide of the present invention, the manganese ion concentration in the supplemental manganese solution supplied to the electrolytic cell is 40 g / L or more. By setting the manganese ion concentration in the supplemental manganese solution to 40 g / L or more, the micropore area is 45 m ² / g to 90 m ² / g and the twin rate in the crystal structure is 40% to 80%. The following electrolytic manganese dioxide can be produced.

Method for producing electrolytic manganese dioxide of the present invention, the electrolysis current density is 0.1 A / dm ² or more 1.0A / dm ² or less. When the electrolytic current density is less than 0.1 A / dm ² , the micropore area is decreased and the productivity is extremely decreased, which is not preferable. On the other hand, if it is 1.0 dm ² or more, the twin rate increases, which is not preferable. Productivity and micropore area, from the viewpoint of SoAkiraritsu, preferably the electrolysis current density is 0.2 A / dm ² or more 0.8 A / dm ² or less, 0.25A / dm ² or more 0.6 A / dm More preferably, it is ² or less.

In the method for producing electrolytic manganese dioxide of the present invention, the number of electrolysis days is 15 days or less. Productivity improves by making electrolysis days into 15 days or less. For example, 1 to 5 days, 7 to 15 days, and the like can be given.

The electrolysis temperature is preferably 90 ° C. or higher and 99 ° C. or lower in order to maintain manufacturing efficiency by maintaining current efficiency, suppress evaporation of the electrolytic solution, and prevent an increase in heating cost. The electrolysis temperature is more preferably 93 ° C. or more and 97 ° C. or less, and further preferably 95 ° C. or more and 97 ° C. or less from the viewpoint of current efficiency and heating cost.

Use a sulfuric acid-manganese sulfate mixed solution as the electrolyte in the electrolytic cell. In addition, the sulfuric acid concentration here is a value excluding sulfate ions of manganese sulfate. The sulfuric acid in the electrolytic solution is controlled as the sulfuric acid concentration, and the sulfuric acid concentration during the electrolysis period can be made constant, or the sulfuric acid concentration can be arbitrarily changed during the electrolysis period.

The sulfuric acid concentration in the electrolytic solution at the start of electrolysis is 44 g / L or more and 50 g / L or less. When the sulfuric acid concentration in the electrolytic solution at the start of electrolysis is less than 44 g / L, the micropore area of the obtained electrolytic manganese dioxide tends to be small, and as a result, the high-rate characteristics are likely to deteriorate. On the other hand, when it exceeds 50 g / L, a passive film is likely to be formed on the surface of the titanium electrode during electrolysis, and as a result, peeling of manganese dioxide deposited on the titanium electrode is likely to occur, resulting in poor electrodeposition.

In particular, the sulfuric acid concentration at the end of electrolysis can be controlled to be higher than the sulfuric acid concentration at the start of electrolysis. In this case, the sulfuric acid concentration during the electrolysis period or at the start of electrolysis is 44 g / L or more and 50 g / L or less, and the reason is as described above. Further, the sulfuric acid concentration at the end of electrolysis is preferably 45 g / L or more and 80 g / L or less. By arbitrarily changing the sulfuric acid concentration in this way, electrolysis with a relatively low sulfuric acid concentration in the first half reduces corrosion damage to the electrode substrate, making it easy to obtain highly filled manganese dioxide with high crystallinity. Electrolysis with a relatively high concentration of sulfuric acid in the second half makes the electrode base material less susceptible to corrosion damage because it is already covered with the electrolytic manganese dioxide deposition layer, and further increases the alkaline potential in addition to the features of the first half. Thus, it becomes easy to obtain electrolytic manganese dioxide excellent in high rate characteristics. In addition, the sulfuric acid concentration during electrolysis is not gradually changed from the start of electrolysis to the end of electrolysis, but the sulfuric acid concentration can be switched between the first half and the second half of electrolysis. There is no restriction on the ratio of electrolysis in the first half and electrolysis in the second half. For example, the ratio of electrolysis time at low sulfuric acid concentration and high sulfuric acid concentration is in the range of 1: 9 to 9: 1, particularly 3: 7 to 7: 3. preferable.

The method for producing electrolytic manganese dioxide of the present invention can also be performed by a so-called suspension electrolysis method in which particles of manganese oxide or the like are continuously mixed in a sulfuric acid-manganese sulfate mixed solution.

The method for producing electrolytic manganese dioxide of the present invention is to grind electrolytic manganese dioxide obtained by electrolysis. For crushing, for example, a jaw crusher, a roller mill, a ball mill, a jet mill or the like can be used. Examples of the roller mill include a centrifugal roller mill and a saddle type Roche mill. Among roller mills, it has excellent cost and durability and is suitable for industrial use, so it can grind raw materials with micro Vickers hardness of 400HV (JIS Z 2244) or higher, and mill motor of 20kW or more and 150kW or less A roller mill having is preferred.

In addition, electrolytic manganese dioxide pulverized by a roller mill can be mixed with electrolytic manganese dioxide having a mode diameter smaller than 1 μm or less. The mixing amount of manganese dioxide with a smaller mode particle size and fine particles of 1 μm or less is mixed in an amount not exceeding the weight of electrolytic manganese dioxide pulverized by a roller mill, and the total weight% is 10 wt% or more and 40 wt% or less. preferable. As a mixing method, dry mixing is preferable in terms of cost. In wet mixing, fine particles of 1 μm or less generated by pulverization with a roller mill or the like can be obtained by adjusting the pH of the mixed slurry to 2.5 to 6.5. It is more preferable because it is aggregated on the surface of larger particles, and the deterioration of workability due to the fine particles is improved. The particle size distribution may be adjusted by classification after pulverization, or may be adjusted by dry air classification or wet dispersion classification.

The method of using the electrolytic manganese dioxide of the present invention as a positive electrode active material of an alkaline manganese dry battery is not particularly limited, and can be used as a positive electrode mixture by mixing with additives by a known method. For example, a mixed powder obtained by adding carbon for imparting conductivity to electrolytic manganese dioxide, an electrolytic solution, and the like, and forming a powder molded body that is pressure-molded into a disk shape or a ring shape can be used as a battery positive electrode.

It is a schematic diagram of the cell for electrochemical measurements. 2 is a pore distribution of electrolytic manganese dioxide obtained in Example 1. 2 is a discharge curve of electrolytic manganese dioxide obtained in Example 1. 2 is an enlarged view (0 to 0.2 seconds) of a discharge curve of electrolytic manganese dioxide obtained in Example 1. FIG. 2 is a particle size distribution of electrolytic manganese dioxide obtained in Example 1. FIG. 2 is a particle size distribution of electrolytic manganese dioxide obtained in Example 2. FIG. 3 is a particle size distribution of electrolytic manganese dioxide obtained in Example 3. 4 is a particle size distribution of electrolytic manganese dioxide obtained in Example 4. 4 is a particle size distribution of electrolytic manganese dioxide obtained in Example 5. 4 is a particle size distribution of electrolytic manganese dioxide obtained in Example 6. 3 is a particle size distribution of electrolytic manganese dioxide obtained in Example 7. FIG. 4 is a particle size distribution of electrolytic manganese dioxide obtained in Example 8. 4 is a particle size distribution of electrolytic manganese dioxide obtained in Example 9. 4 is a particle size distribution of electrolytic manganese dioxide obtained in Example 10. 4 is a particle size distribution of electrolytic manganese dioxide obtained in Example 11. 2 is a particle size distribution of electrolytic manganese dioxide obtained in Comparative Example 1. FIG. 3 is a particle size distribution of electrolytic manganese dioxide obtained in Comparative Example 2. 4 is a particle size distribution of electrolytic manganese dioxide obtained in Comparative Example 3.

Hereinafter, the present invention will be described in detail with reference to examples and comparative examples, but the present invention is not limited to these examples.

<Measurement of micropore area>
The micropore area of electrolytic manganese dioxide was measured using a high-precision, multi-analyte gas adsorption amount measuring device (trade name: Autosorb-iQ, manufactured by Cantachrome Instruments Japan GK). After dehydration at 150 ° C. for 4 hours while evacuating, the amount of adsorbed argon was measured in the pressure range of 87 K and 0.0001 to 760 Torr using argon as an adsorbent. A pore distribution is calculated by applying the NLDFT method to the obtained adsorption isotherm, and the pore area in the range of 0.46 to 1.95 nm is the micropore area, and the range of 1.95 to 49.0 nm. The pore area of each pore was defined as the mesopore area. In the NLDFT method, fitting was performed using a cylindrical pore model of zeolite / silica.

<Measurement of twin rate and half width (full width at half maximum: FWHM) by XRD measurement>
The twin rate and half width (FWHM) of electrolytic manganese dioxide were measured and calculated using an X-ray diffractometer (trade name: MXP-3, manufactured by Mac Science). 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 10 ° to 80 ° as 2θ. Measured with

The twin rate is obtained from the XRD measurement result after obtaining the plane distance between the (061) plane and the (021) plane, and then the reference (Reference 1: Progress in Solid State Chemistry, Vol. 23, pp. 1-130, 1995, (Reference Document 2: Tosoh Research Report, Vol. 49, p. 21-27, 2005) was calculated from the b-axis and c-axis lengths of the crystal lattice by the following formula.

The full width at half maximum (FWHM) was obtained by calculating the full width at half maximum of the (110) plane from diffraction lines with 2θ of around 22 ± 1 °.

<Measurement of alkali potential>
The alkaline potential of electrolytic manganese dioxide was measured in a 40 wt% KOH aqueous solution as follows.

0.9 g of carbon as a conductive agent was added to 3 g of electrolytic manganese dioxide to obtain a mixed powder, and 4 ml of 40% KOH aqueous solution was added to this mixed powder to obtain a mixture slurry of electrolytic manganese dioxide, carbon and KOH aqueous solution. The alkaline potential of the electrolytic manganese dioxide was measured with respect to the potential of the mixture slurry with reference to a mercury / mercury oxide reference electrode.

<Measurement of sulfate radical and sodium content>
The sulfate radical and sodium content of electrolytic manganese dioxide were quantified by dissolving electrolytic manganese dioxide in nitric acid and hydrogen peroxide solution, and measuring this solution with ICP.

<Measuring method of particle size composition of electrolytic manganese dioxide>
The particle size composition of electrolytic manganese dioxide was measured according to the following method. 0.03 g of electrolytic manganese dioxide is added to 20 ml of pure water, pH is adjusted to 8 by adding ammonia water, and then a dispersion slurry is prepared by ultrasonic irradiation. Microtrac MT3300EXII (manufactured by Microtrac Bell) and SDC circulation The particle size distribution was measured in the HRA mode using a container (manufactured by Microtrack Bell). At this time, in order to disperse fine particles having a size of 1 μm or less in an aggregated state and measure an accurate amount, it is necessary to perform a dispersion treatment such as ultrasonic irradiation. If the dispersion treatment is not performed, the amount of fine particles cannot be measured accurately because measurement is performed in a state where the fine particles are aggregated. Further, when calculating the volume frequency distribution, 101 sections (704.00, 645.60, 592.00, 542...) That match the 101 channels for measurement set in the particle size distribution measuring apparatus by non-spherical approximation. 90, 497.80, 456.50, 418.60, 383.90, 352.00, 322.80, 296.00, 271.40, 248.90, 228.20, 209.30, 191.90, 176.00, 161.40, 148.00, 135.70, 124.50, 114.10, 104.70, 95.96, 88.00, 80.70, 74.00, 67.86, 62. 23, 57.06, 52.33, 47.98, 44.00, 40.35, 37.00, 33.93, 31.11, 28.53, 26.16, 23.99, 22.00, 2 .17, 18.50, 16.96, 15.56, 14.27, 13.08, 12.00, 11.00, 10.09, 9.25, 8.48, 7.78, 7.13 6.54, 6.00, 5.50, 5.04, 4.63, 4.24, 3.89, 3.57, 3.27, 3.00, 2.75, 2.52, 2 .31, 2.12, 1.95, 1.78, 1.64, 1.50, 1.38, 1.26, 1.16, 1.06, 0.97, 0.89, 0.82 0.75, 0.69, 0.63, 0.58, 0.53, 0.49, 0.45, 0.41, 0.38, 0.34, 0.32, 0.29, 0 27, 0.24, 0.22, 0.20, 0.19, 0.17, 0.16, 0.15, 0.13, 0.12 / μm).

<Measurement of BET specific surface area>
The BET specific surface area of electrolytic manganese dioxide was measured by nitrogen adsorption according to the BET one-point method. A gas adsorption specific surface area measuring device (Flowsorb III, manufactured by Shimadzu Corporation) was used as the measuring device. Prior to measurement, the electrolytic manganese dioxide was dehydrated by heating at 150 ° C. for 1 hour.

<Measurement of press density>
The press density of electrolytic manganese dioxide is obtained by pressing 0.5 g of electrolytic manganese dioxide at 2 t / cm ² using a 13 mmφ mold and holding it for 60 seconds to produce a molded body. The press density is determined from the weight and volume of the molded body. Asked.

<Measurement of average particle diameter>
The average particle diameter of electrolytic manganese dioxide was measured in HRA mode using Microtrac MT3300EXII (manufactured by Microtrac Bell).

<Measurement of voltage drop 1 and voltage drop 2>
A mixture was prepared by mixing 90% by weight of electrolytic manganese dioxide, 7% by weight of graphite (trade name: KS-44, manufactured by Lonza) and 3% by weight of polytetrafluoroethylene (manufactured by Aldrich). A positive electrode is formed by pressure bonding to a mesh made at 2 t / cm ² , and a positive electrode, a separator, a 40 wt% KOH aqueous solution, and a negative electrode (zinc wire) are placed in a polyvinyl chloride container, and an electrochemical measurement cell (FIG. 1) is installed. Produced. After measuring the open circuit voltage (open circuit voltage 1), a constant current (100 mA for 1 g of electrolytic manganese dioxide) was passed between the positive electrode and the negative electrode for 60 seconds, and the voltage of the single electrode of the positive electrode was mercury / oxidized. Measurements were made based on a mercury reference electrode. After passing the current for 60 seconds, the current was interrupted, and after 6 hours, the open circuit voltage (open circuit voltage 2) was measured, and the open circuit voltage drop was calculated by subtracting the open circuit voltage 2 from the open circuit voltage 1. A voltage drop from 50 ms after starting to flow current was defined as a voltage drop 1, and a value obtained by subtracting an open circuit voltage drop from a voltage drop from 50 ms to 60 seconds was defined as a voltage drop 2. The voltage drop was measured when the electrolytic manganese dioxide was in an undischarged state, 25% discharge, and 50% discharge. Electrolytic manganese dioxide in a 25% discharge state and a 50% discharge state was produced by discharging the electrolytic manganese dioxide at a capacity restriction of 308 mAh / g. The 25% discharge state simulates a state where the lower limit voltage (1.05V) is reached by 1.5W discharge (ANSI standard discharge), which is an evaluation of high rate discharge characteristics of an alkaline manganese dry battery, and a 50% discharge state. Is a simulation of a state in which the discharge lower limit voltage (0.9 V) has been reached in 1 A discharge (ANSI standard discharge), which is also a high-rate discharge characteristic evaluation.

<Measurement of charge transfer resistance>
The charge transfer resistance of the positive electrode single electrode was measured by the alternating current impedance method using the electrochemical measurement cell (FIG. 1) produced by the above method. For the evaluation, an AC impedance measuring device (ECI1287A, FRA1255A, manufactured by Toyo Technica Co., Ltd.) was used, and measurement was performed at a measurement frequency of 120,000 Hz to 0.1 Hz and an AC voltage of ± 5 mV. The measurement data was analyzed by Nyquist plot, and the diameter of the semicircular arc component was taken as the charge transfer resistance. The charge transfer resistance was measured when the electrolytic manganese dioxide was in an undischarged state, 25% discharge, and 50% discharge.

Example 1
Electrolysis was carried out using an electrolytic cell that had a heating device and suspended a titanium plate as an anode and a graphite plate as a cathode so as to face each other.

Supplying a manganese sulfate solution with a manganese ion concentration of 65 g / L to the electrolytic cell, maintaining an electrolytic current density of 0.34 A / dm ² and a temperature of the electrolytic cell at 97 ° C. L was adjusted to 77 g / L, and electrolysis was carried out for 15 days in total, 10 days with the sulfuric acid concentration in the first half and 5 days with the sulfuric acid concentration in the second half.

After electrolysis, the electrodeposited plate-like electrolytic manganese dioxide was washed with pure water, pulverized with a jaw crusher, and then pulverized with a ball mill to obtain an electrolytic manganese dioxide pulverized product. Next, this electrolytic manganese dioxide pulverized product is put into a water tank, and an aqueous sodium hydroxide solution is added while stirring, and the slurry is neutralized so as to have a pH of 2.8. Water washing, filtration separation, and drying were performed. Next, an electrolytic manganese dioxide powder was obtained through a sieve having an aperture of 63 μm.

The pore distribution of the obtained electrolytic manganese dioxide is shown in FIG. 2, the discharge curve is shown in FIG. 3, the enlarged view of the discharge curve (0 to 0.2 seconds) is shown in FIG. 4, and the particle size distribution is shown in FIG. Table 1 shows evaluation results such as area and twin rate.

The voltage drop 1, voltage drop 2 and charge transfer resistance of the obtained electrolytic manganese dioxide are shown in Table 2.

Example 2
Electrolysis was carried out in the same manner as in Example 1 except that a replenished manganese sulfate solution having a manganese ion concentration of 55 g / L was supplied and that the sulfuric acid concentrations in the initial electrolysis and the latter electrolysis were 46 g / L and 65 g / L. . The particle size distribution of the obtained electrolytic manganese dioxide is shown in FIG. 6, and the evaluation results such as the micropore area and the twin rate are shown in Table 1. Further, Table 2 shows voltage drop 1, voltage drop 2 and charge transfer resistance of the obtained electrolytic manganese dioxide.

Example 3
Supplying manganese sulfate solution with a manganese ion concentration of 45 g / L, maintaining the temperature of the electrolytic cell at 96 ° C., conducting electrolysis for 7 days while maintaining the sulfuric acid concentration at 45 g / L, and neutralizing Electrolysis was carried out in the same manner as in Example 1 except that the pH at that time was 5. The particle size distribution of the obtained electrolytic manganese dioxide is shown in FIG. 7, and the evaluation results such as the micropore area and twin rate are shown in Table 1. Further, Table 2 shows voltage drop 1, voltage drop 2 and charge transfer resistance of the obtained electrolytic manganese dioxide.

Example 4
Example except that a replenished manganese sulfate solution having a manganese ion concentration of 100 g / L was supplied, that the temperature of the electrolytic cell was maintained at 96 ° C., and electrolysis was performed for one day while maintaining the sulfuric acid concentration at 44 g / L. Electrolysis was performed in the same manner as in 1. The particle size distribution of the obtained electrolytic manganese dioxide is shown in FIG. 8, and the evaluation results such as the micropore area and the twin rate are shown in Table 1. Further, Table 2 shows voltage drop 1, voltage drop 2 and charge transfer resistance of the obtained electrolytic manganese dioxide.

Example 5
Grinding was performed in the same manner as in Example 1 to obtain a ground product of electrolytic manganese dioxide. Pure water was added to the obtained electrolytic manganese dioxide powder to prepare a slurry, which was subjected to dispersion treatment by ultrasonic irradiation and then allowed to stand for 20 minutes. Then, it decanted and isolate | separated into the residue and the supernatant slurry. The residue was dried at 60 ° C. to obtain an electrolytic manganese dioxide powder having a relatively large particle size of 10 μm or more. The supernatant slurry was filtered and dried at 60 ° C. to obtain a relatively small electrolytic manganese dioxide powder of 10 μm or less. Thereafter, electrolytic manganese dioxide of 10 μm or more and electrolytic manganese dioxide of 10 μm or less were mixed at a weight ratio of 2: 1. The particle size distribution of the obtained electrolytic manganese dioxide is shown in FIG. 9, and the evaluation results such as the micropore area and twin rate are shown in Table 1. Further, Table 2 shows voltage drop 1, voltage drop 2 and charge transfer resistance of the obtained electrolytic manganese dioxide.

Example 6
Electrolytic manganese dioxide was obtained in the same manner as in Example 5 except that 10 μm or more of electrolytic manganese dioxide and 10 μm or less of electrolytic manganese dioxide were mixed at a weight ratio of 5: 4. The particle size distribution of the obtained electrolytic manganese dioxide is shown in FIG. 10, and the evaluation results such as the micropore area and the twin rate are shown in Table 1. Further, Table 2 shows voltage drop 1, voltage drop 2 and charge transfer resistance of the obtained electrolytic manganese dioxide.

Example 7
Electrolysis was carried out in the same manner as in Example 1 except that a replenished manganese sulfate solution having a manganese ion concentration of 74 g / L was supplied and that the sulfuric acid concentrations in the initial electrolysis and the latter electrolysis were 45 g / L and 75 g / L. . The particle size distribution of the obtained electrolytic manganese dioxide is shown in FIG. 11, and the evaluation results such as the micropore area and twin rate are shown in Table 1. Further, Table 2 shows voltage drop 1, voltage drop 2 and charge transfer resistance of the obtained electrolytic manganese dioxide.

Example 8
Electrolysis was carried out in the same manner as in Example 1 except that a replenished manganese sulfate solution having a manganese ion concentration of 55 g / L was supplied and that electrolysis was performed for 15 days while maintaining the sulfuric acid concentration at 55 g during electrolysis. The particle size distribution of the obtained electrolytic manganese dioxide is shown in FIG. 12, and the evaluation results such as the micropore area and twin rate are shown in Table 1. Further, Table 2 shows voltage drop 1, voltage drop 2 and charge transfer resistance of the obtained electrolytic manganese dioxide.

Example 9
Supplying a replenished manganese sulfate solution with a manganese ion concentration of 84 g / L, an electrolysis current density of 0.55 A / dm ^2, and sulfuric acid concentrations of 45 g / L and 65 g / L in the initial electrolysis and the latter electrolysis Except for this, electrolysis was performed in the same manner as in Example 1. The particle size distribution of the obtained electrolytic manganese dioxide is shown in FIG. 13, and the evaluation results such as the micropore area and the twin rate are shown in Table 1. Further, Table 2 shows voltage drop 1, voltage drop 2 and charge transfer resistance of the obtained electrolytic manganese dioxide.

Example 10
Supplying a replenished manganese sulfate solution with a manganese ion concentration of 74 g / L, an electrolysis current density of 0.55 A / dm ^2, and sulfuric acid concentrations of 45 g / L and 65 g / L in the initial and second half of electrolysis Except for this, electrolysis was performed in the same manner as in Example 1. The particle size distribution of the obtained electrolytic manganese dioxide is shown in FIG. 14, and the evaluation results such as the micropore area and the twin rate are shown in Table 1. Further, Table 2 shows voltage drop 1, voltage drop 2 and charge transfer resistance of the obtained electrolytic manganese dioxide.

Example 11
Supplying a replenished manganese sulfate solution having a manganese ion concentration of 55 g / L, an electrolysis current density of 0.40 A / dm ^2, and sulfuric acid concentrations of 46 g / L and 65 g / L in the initial and second half of electrolysis Except for this, electrolysis was performed in the same manner as in Example 1. The particle size distribution of the obtained electrolytic manganese dioxide is shown in FIG. 15, and the evaluation results such as the micropore area and twin rate are shown in Table 1. Further, Table 2 shows voltage drop 1, voltage drop 2 and charge transfer resistance of the obtained electrolytic manganese dioxide.

Comparative Example 1
Supplying manganese sulfate solution with a manganese ion concentration of 19 g / L, maintaining the temperature of the electrolytic cell at 96 ° C., performing electrolysis for 10 days while maintaining the sulfuric acid concentration at 19 g / L, and neutralizing Electrolysis was carried out in the same manner as in Example 1 except that the pH at that time was 5. The particle size distribution of the obtained electrolytic manganese dioxide is shown in FIG. 16, and the evaluation results such as the micropore area and the twin rate are shown in Table 1. Further, Table 2 shows voltage drop 1, voltage drop 2 and charge transfer resistance of the obtained electrolytic manganese dioxide.

Comparative Example 2
Supplying a replenished manganese sulfate solution with a manganese ion concentration of 30 g / L, maintaining the electrolytic bath temperature at 96 ° C., conducting electrolysis for 1 day while maintaining the sulfuric acid concentration at 28 g / L, and neutralization Electrolysis was carried out in the same manner as in Example 1 except that the pH at that time was 5. The particle size distribution of the obtained electrolytic manganese dioxide is shown in FIG. 17, and the evaluation results such as the micropore area and twin rate are shown in Table 1. Further, Table 2 shows voltage drop 1, voltage drop 2 and charge transfer resistance of the obtained electrolytic manganese dioxide.

Comparative Example 3
A method similar to that of Example 1 except that a replenished manganese sulfate solution having a manganese ion concentration of 55 g / L was supplied and that the sulfuric acid concentrations in the initial electrolysis and the latter electrolysis were adjusted to 38 g / L and 65 g / L. Electrolysis was performed. The particle size distribution of the obtained electrolytic manganese dioxide is shown in FIG. 18, and the evaluation results such as the micropore area and twin rate are shown in Table 1. Further, Table 2 shows voltage drop 1, voltage drop 2 and charge transfer resistance of the obtained electrolytic manganese dioxide.

From Tables 1 and 2, by producing electrolytic manganese dioxide at the manganese ion concentration of Examples 1 to 11, electrolytic manganese dioxide having a larger micropore area and a lower twin rate than Comparative Examples 1 and 2. In addition, by producing electrolytic manganese dioxide at a sulfuric acid concentration in the electrolytic solution at the start of electrolysis in Examples 1 to 11, electrolytic manganese dioxide having a smaller twin rate than that in Comparative Example 3 can be obtained. Obtainable. Furthermore, the electrolytic manganese dioxides of Examples 1 to 11 have a smaller voltage drop 1 + voltage drop 2 than those of Comparative Examples 1 to 3, and excellent high-rate discharge characteristics can be expected.

The specification, claims, drawings and abstract of Japanese Patent Application No. 2017-61561 filed on March 27, 2017 and Japanese Patent Application No. 2017-222472 filed on November 22, 2017. Is hereby incorporated by reference as a disclosure of the specification of the present invention.

Since the electrolytic manganese dioxide of the present invention has a specific micropore area and twin rate in the crystal structure, it should be used as a positive electrode active material for manganese batteries, particularly alkaline manganese batteries, having excellent discharge characteristics, particularly high-rate discharge characteristics. Can do.

Claims

An electrolytic manganese dioxide having a micropore area of 45 m 2 / g or more and 90 m 2 / g or less, and a twin rate in a crystal structure of 40% or more and 80% or less.
2. The electrolytic manganese dioxide according to claim 1, wherein the alkaline potential is 250 mV or more and 310 mV or less.
The electrolytic manganese dioxide according to claim 1 or 2, wherein the content of sulfate radical (SO 4 ) is 1.5% by weight or less.
The electrolytic manganese dioxide according to any one of claims 1 to 3, wherein the sodium content is 10 ppm by weight or more and 5,000 ppm by weight or less.
1. The value of (B) / (A) is 0.90 or more for the mode particle size (A) in the volume frequency distribution and the particle size width (B) that is 1/2 the mode particle size (A). The electrolytic manganese dioxide according to any one of claims 1 to 4, wherein the electrolytic manganese dioxide is 0 or less.
6. The electrolytic manganese dioxide according to claim 1, wherein the average particle size is 20 μm or more and 50 μm or less.
Manganese ion concentration in the replenishment manganese liquid supplied to the electrolytic cell is 40 g / L or more, the electrolytic current density is 0.1 A / dm 2 or more 1.0A / dm 2 or less, sulfuric acid in the electrolytic solution at the initiation of the electrolysis The method for producing electrolytic manganese dioxide according to any one of claims 1 to 6, wherein the concentration is 44 g / L or more and 50 g / L or less, and the number of days of electrolysis is 15 days or less.
A sulfuric acid-manganese sulfate mixed solution whose sulfuric acid concentration in the electrolytic solution at the end of electrolysis is higher than the sulfuric acid concentration in the electrolytic solution at the start of electrolysis is used, and the sulfuric acid concentration in the electrolytic solution at the end of electrolysis is 32 g / L is 80 g / L or less, The manufacturing method of the electrolytic manganese dioxide of Claim 7 characterized by the above-mentioned.
A positive electrode active material for a battery, comprising the electrolytic manganese dioxide according to any one of claims 1 to 6.
A battery comprising the battery positive electrode active material according to claim 9.