JP7127291B2 - Electrolytic manganese dioxide, method for producing the same, and use thereof - Google Patents

Description

TECHNICAL FIELD The present invention relates to electrolytic manganese dioxide used as a positive electrode active material in batteries such as manganese dry batteries, particularly alkaline manganese dry batteries and lithium ion primary batteries, a method for producing the same, and uses thereof.

Manganese dioxide is known, for example, as a positive electrode active material for manganese dry batteries or alkaline manganese dry batteries, and has the advantages of excellent storage stability and low cost. In particular, alkaline manganese dry batteries that use manganese dioxide as a positive electrode active material are widely used in electronic cameras, portable tape recorders, portable information devices, game machines and toys because of their excellent discharge characteristics under heavy loads. , the demand for which has grown rapidly in recent years.

However, in alkaline manganese dry batteries, as the discharge current increases, the utilization rate of manganese dioxide, which is the positive electrode active material, decreases, and since it cannot be used in a state where the discharge voltage is lowered, the actual discharge capacity is greatly impaired. was there. In other words, when alkaline manganese dry batteries are used in devices that use large currents (high-rate discharge), manganese dioxide, which is the positive electrode active material, is not fully utilized, resulting in a short operating time. rice field.

Therefore, manganese dioxide that can exhibit high capacity and long life even under high-rate intermittent discharge conditions in which a large current is drawn out in a short time, that is, manganese dioxide that is excellent in so-called high-rate discharge characteristics has been desired.

So far, in order to improve high-rate discharge characteristics, it has been studied to produce electrolytic manganese dioxide with a small half-value width of the (110) plane (Patent Documents 1 and 2).

However, in order to reduce the half-value width of the (110) plane of electrolytic manganese dioxide, it is necessary to reduce the current density during electrolysis, resulting in a problem of low productivity.

Although it is also being considered to produce electrolytic manganese dioxide by mixing a cationic surfactant in the electrolyte (Non-Patent Document 1), the temperature during electrolysis is as high as 100 ° C. or higher, so the half-value width is No effect of reducing .

JP 2009-135067 A JP 2017-179583 A

Journal of Power Sources, 141 (2005), p. 340-350

The object of the present invention is to provide a (110) plane with a small half-value width, a small amount of structural water, a large content of manganese dioxide with respect to the whole, a crystal structure maintained by the carbon content of the contained surfactant, and excellent high-rate discharge characteristics. An object of the present invention is to provide electrolytic manganese dioxide, a method for producing the same with high productivity, and uses thereof.

In particular, the present inventors have extensively studied a method for producing manganese dioxide, which is used as a positive electrode active material for alkaline manganese dry batteries. It is possible to obtain electrolytic manganese dioxide in which the half-value width of the (110) plane is small, the amount of structural water is small, the content of manganese dioxide with respect to the whole is large, and the crystal structure is maintained by the carbon content of the contained surfactant. Furthermore, the inventors have found that it can be produced at a high current density with high productivity, and have completed the present invention. That is, in the present invention, the half width of the (110) plane in XRD measurement using a CuKα ray as a light source is 1.4 ° or more and 2.5 ° or less, and the structural water content calculated from the weight loss at 240 ° C. is 1.4 wt. % or more and 2.1 wt% or less and a carbon weight fraction of 0.02 wt% or more and 1.0 wt% or less, and an electrolytic manganese dioxide and a cationic surfactant are mixed in the electrolytic solution and electrodeposited at 98 ° C. or less. A method for producing electrolytic manganese dioxide.

The present invention will be described in detail below.

The electrolytic manganese dioxide of the present invention has a half width of the (110) plane of 1.4° or more and 2.5° or less in XRD measurement using a CuKα ray as a light source. If the half width of the (110) plane in XRD measurement using a CuKα ray as a light source exceeds 2.5°, the crystallinity is not sufficient, and if it is less than 1.4°, the crystallinity becomes too high, [H + ] It is presumed that the discharge performance is lowered because the number of hydroxyl groups such as structural defects effective for diffusion is reduced. The half width is preferably 1.5° or more and 2.5° or less.

The electrolytic manganese dioxide of the present invention has a structural water content of 1.4 wt % or more and 2.1 wt % or less calculated from the weight loss at 240°C. If the amount of structural water calculated from the weight loss at 240° C. is less than 1.4 wt %, hydroxyl groups such as structural defects effective for [H+] diffusion are reduced, and discharge performance is presumed to be lowered. If it exceeds 2.1 wt%, it is presumed that the content of manganese dioxide with respect to the whole decreases and the discharge performance deteriorates. The amount of structural water is preferably 1.45 wt % or more and 2.05 wt % or less.

The electrolytic manganese dioxide of the present invention has a carbon weight fraction of 0.02 wt % or more and 1.0 wt % or less. If the carbon weight fraction is less than 0.02 wt%, the crystallinity of the manganese dioxide maintained by the carbon content of the cationic surfactant or the like is not sufficient, resulting in a decrease in discharge performance. If it exceeds 1.0 wt%, the content of manganese dioxide with respect to the whole decreases, and the discharge performance deteriorates. The carbon weight fraction is preferably 0.3 wt % or more and 0.9 wt % or less.

In the method for producing electrolytic manganese dioxide of the present invention, a cationic surfactant is added to the electrolytic solution in the electrolysis step.

Although the cationic surfactant in the present invention is not particularly limited, examples thereof include at least one of alkylamines, alkylamine salts and quaternary ammonium salts. Examples of alkylamines include octylamine, decylamine, tetradecylamine, hexadecylamine, octadecylamine, methyloctylamine, methyldecylamine, methyltetradecylamine, methylhexadecylamine, methyloctadecylamine, dimethyloctylamine, dimethyl Examples include decylamine, dimethyltetradecylamine, dimethylhexadecylamine, dimethyloctadecylamine, etc. Examples of alkylamine salts include octylamine hydrochloride, decylamine hydrochloride, tetradecylamine hydrochloride, hexadecylamine hydrochloride, Examples include octadecylamine hydrochloride, and quaternary ammonium salts include, for example, octyltrimethylammonium chloride, dodecyltrimethylammonium chloride, hexadecyltrimethylammonium chloride, octadecyltrimethylammonium chloride, docosyltrimethylammonium chloride, and octyltrimethylammonium bromide. , dodecyltrimethylammonium bromide, hexadecyltrimethylammonium bromide, octadecyltrimethylammonium bromide, docosyltrimethylammonium bromide, octyltrimethylammonium hydroxide, dodecyltrimethylammonium hydroxide, hexadecyltrimethylammonium hydroxide, octadecyltrimethylammonium hydroxide, docosyl Trimethylammonium hydroxide, tetramethylammonium hydroxide, tetrabutylammonium hydroxide, tetrabutylammonium hydroxide, tetrahexylammonium hydroxide, tetraoctylammonium hydroxide, benzyldimethylstearylammonium chloride, benzyldimethylstearylammonium bromide, benzyldimethylstearyl Ammonium hydroxide etc. can be illustrated.

The total number of carbon atoms in the cationic surfactant in this case is preferably 20 or more. Examples of those having a total number of carbon atoms of 20 or more include dimethyloctadecylamine, octadecyltrimethylammonium chloride, docosyltrimethylammonium chloride, octadecyltrimethylammonium bromide, docosyltrimethylammonium bromide, octadecyltrimethylammonium hydroxide, doco siltrimethylammonium hydroxide, tetrahexylammonium hydroxide, tetraoctylammonium hydroxide, benzyldimethylstearylammonium chloride, benzyldimethylstearylammonium bromide, benzyldimethylstearylammonium hydroxide and the like. Also, it preferably contains one or more alkyl groups having 17 or more carbon atoms. Examples of compounds containing one or more alkyl groups having 17 or more carbon atoms include dimethyloctadecylamine, octadecyltrimethylammonium chloride, docosyltrimethylammonium chloride, octadecyltrimethylammonium bromide, docosyltrimethylammonium bromide, and octadecyltrimethylammonium. hydroxide, docosyltrimethylammonium hydroxide, benzyldimethylstearylammonium chloride, benzyldimethylstearylammonium bromide, benzyldimethylstearylammonium hydroxide and the like.

In the method for producing electrolytic manganese dioxide of the present invention, the temperature during electrodeposition is 98° C. or less. Electrolytic manganese dioxide having a small half width of the (110) plane can be obtained by electrodepositing at a temperature of 98° C. or lower and adding a cationic surfactant. The electrolysis temperature maintains the production efficiency by maintaining the current efficiency, suppresses the evaporation of the electrolyte, prevents the increase in heating cost, and reduces the half-value width of the cationic surfactant. It is preferable to carry out at 90° C. or higher and 98° C. or lower. From the viewpoint of current efficiency and heating cost, the electrolysis temperature is more preferably 93°C or higher and 97°C or lower, and even more preferably 95°C or higher and lower than 97°C.

In the method for producing electrolytic manganese dioxide of the present invention, the electrolytic current density is not particularly limited, but in order to improve productivity and further prevent corrosion damage to the electrode substrate, it should be 0.2 A/dm ² or more. It is preferably less than 5 A/ ^dm2 . From the viewpoint of productivity and stable production, the electrolytic current density is more preferably 0.29 A/dm ² or more and 1.4 A/dm ² or less, and 0.29 A/dm ² or more and 1.35 A/dm ² or less. is more preferred.

An aqueous manganese salt solution can be used as the electrolytic solution in the electrolytic cell. Manganese salts are not particularly limited, but examples include manganese nitrate, manganese chloride, and manganese sulfate. The electrolytic solution can be mixed with an acid such as nitric acid, hydrochloric acid, sulfuric acid, and the like. Hereinafter, a sulfuric acid-manganese sulfate mixed solution will be described as an example, but the present invention is not particularly limited to this. The sulfuric acid concentration referred to herein is a value excluding the sulfate ion of manganese sulfate. Sulfuric acid in the electrolytic solution is controlled as sulfuric acid concentration and is not particularly limited, but for example, 10 to 75 g/L can be exemplified. The sulfuric acid concentration can be kept constant during the electrolysis period, and the sulfuric acid concentration can be arbitrarily changed during the electrolysis period. In particular, the sulfuric acid concentration at the end of the electrolysis can be controlled to be higher than the sulfuric acid concentration at the start of the electrolysis. can also

In this case, the sulfuric acid concentration during the electrolysis period or at the start of electrolysis is preferably 10 g/L or more and 65 g/L or less, more preferably 13 g/L or more and 60 g/L or less. The concentration of sulfuric acid at the end of electrolysis is preferably 15 g/L or more and 75 g/L or less, more preferably 18 g/L or more and 70 g/L or less. By changing the sulfuric acid concentration arbitrarily in this way, electrolysis is performed with a relatively low concentration of sulfuric acid in the first half, which reduces corrosion damage to the electrode substrate and obtains manganese dioxide with high crystallinity and high filling. In the second half, electrolysis is performed with a relatively high concentration of sulfuric acid, so that the electrode base material is already covered with the deposited layer of electrolytic manganese dioxide, so it is less susceptible to corrosion damage. , it becomes easy to obtain electrolytic manganese dioxide excellent in high rate characteristics. Moreover, instead of gradually changing the sulfuric acid concentration during electrolysis from the start of electrolysis to the end of electrolysis, it is preferable to switch the sulfuric acid concentration between the first half and the second half of electrolysis. The ratio of electrolysis in the first half and electrolysis in the second half is not limited, but for example, the ratio of electrolysis time at low sulfuric acid concentration and high sulfuric acid concentration is 1:9 to 9:1, especially 3:7 to 7:3. preferable.

The concentration of manganese ions in the replenishing manganese sulfate solution supplied to the electrolytic cell is not limited, but can be, for example, 10 to 75 g/L.

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

By using a single-stage pulverization, the particle size structure of the present invention can be obtained at low cost.

Further, by mixing electrolytic manganese dioxide having a smaller mode particle size with pulverized electrolytic manganese dioxide, the mode particle size and particle size distribution width can be controlled to obtain a desired particle size structure. The amount of manganese dioxide having a smaller mode particle size to be mixed is not more than the weight of the pulverized electrolytic manganese dioxide, and the total weight % is preferably 10% by weight or more and 40% by weight or less. As for the mixing method, dry mixing is preferable in terms of cost, and wet mixing is performed by setting the pH of the mixed slurry to 2.5 or more and 6.5 or less, so that fine particles of 1 μm or less are aggregated on the surface of larger particles. easier and more preferable. In addition, the particle size structure may be controlled by classification after pulverization, and the particle size structure, the amount of fine particles of 1 μm or less, and the aggregation state may be adjusted by dry air classification or wet dispersion classification. can also

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

The electrolytic manganese dioxide of the present invention can be suitably used as a positive electrode material for batteries, particularly alkaline manganese dry batteries and lithium ion primary batteries, as a positive electrode material with high performance and good storage characteristics due to its high crystallinity and low structural water content. can be done.

There is no particular limitation on the method of using it as a positive electrode active material for alkaline manganese dry batteries, and it can be used by mixing with additives by a known method. For example, a mixed powder is prepared by adding carbon or the like to impart electrical conductivity to the electrolytic manganese dioxide, and the mixture is pressure-molded into a disc or ring to obtain a battery positive electrode.

When used as a positive electrode active material for a lithium ion primary battery, it is not particularly limited and can be used by mixing with an additive by a known method. For example, baking is performed as a pretreatment, a mixed powder is prepared by adding carbon or the like as a conductive aid and polytetrafluoroethylene or the like as a binder, and the mixed powder is bound to a current collector, or the mixed powder is used as a solvent. A battery positive electrode can be obtained by dispersing to form a slurry, coating, drying, and then press molding.

The electrolytic manganese dioxide of the present invention has a small full width at half maximum (FWHM) of the diffraction line near 22±1° 2θ, a small amount of structural water calculated from the weight loss at 240° C., and a content of manganese dioxide with respect to the whole. In many cases, the crystal structure is maintained by the carbon content of the contained surfactant, and the electrolyte is expected to have excellent high-rate discharge characteristics when used as a positive electrode active material for alkaline manganese dry batteries and lithium-ion primary batteries, and as a positive electrode material for alkaline batteries. It is manganese dioxide, and in the method for producing electrolytic manganese dioxide of the present invention, the electrolytic manganese dioxide can be produced at a high current density with high productivity.

1 is an SEM image (×1,000) of Example 1. FIG.

EXAMPLES 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 Full Width at Half Maximum (FWHM) of (110) Plane in XRD Measurement>
The full width at half maximum (FWHM) of the diffraction line near 22±1° in 2θ of electrolytic manganese dioxide was measured using an X-ray diffractometer (Ultima IV, manufactured by Rigaku). CuKα rays (λ=1.5418 Å) were used as the radiation source, and the measurement mode was a scan speed of 4.00 deg. /min, step width 0.040 deg. , and the measurement range was from 10° to 90° as 2θ.

<Measurement of structural water content>
The amount of structural water calculated from the weight loss of electrolytic manganese dioxide at 240 ° C. is 110 ° C. from the weight loss when held at 240 ° C. for 12 hours using a thermogravimetric analyzer (TG / DTA6300, manufactured by Seiko Instruments). , the amount of weight loss during 16-hour holding was subtracted, divided by the weight during 1-hour holding at 600°C, and expressed as a percentage.

<Measurement of carbon weight fraction>
The carbon weight fraction of electrolytic manganese dioxide was measured by a combustion-infrared absorption method using a carbon/sulfur analyzer (LECO CS844, manufactured by LECO).

<Measurement of BET specific surface area>
The BET specific surface area of electrolytic manganese dioxide was measured by nitrogen adsorption by the BET single-point method. A gas adsorption type specific surface area measuring device (Flowsorb III, manufactured by Shimadzu Corporation) was used as the measuring device. Prior to measurement, the measurement sample was degassed by heating at 150° C. for 40 minutes.

Example 1
A current density of 1.0 A/dm ² , an electrolysis temperature of 97° C., a manganese sulfate solution with a manganese concentration of 39.0 g/l as an electrolysis replenisher, a sulfuric acid concentration of 20.0 g/l, and trimethylstearylammonium chloride of 100 mg/l. L, and electrolyzed for 17 days. After electrolysis, the electrolytic manganese dioxide was pulverized, washed, and then neutralized so that the pH of the slurry was 5.3 to 5.7. Table 1 shows the production conditions, and Table 2 shows the results. Moreover, the SEM image (1,000 times) of Example 1 is shown in FIG. At 100° C. or higher, it clearly differs from the case where a cationic surfactant is added, and exhibits a dense particle shape.

Example 2
Electrolysis and post-treatment were carried out in the same manner as in Example 1, except that trimethylstearylammonium chloride was added so as to be 200 mg/L. Table 1 shows the production conditions, and Table 2 shows the results.

Example 3
Electrolysis and post-treatment were carried out in the same manner as in Example 1, except that trimethylstearylammonium chloride was added so as to be 50 mg/L. Table 1 shows the production conditions, and Table 2 shows the results.

Example 4
Example 1 except that the current density was 0.55 A/dm ² , the electrolysis temperature was 96° C., the electrolytic replenisher was a manganese sulfate solution with a manganese concentration of 48.0 g/L, and the sulfuric acid concentration was 35.3 g/L. Electrolysis and post-treatment were carried out in the same manner. Table 1 shows the production conditions, and Table 2 shows the results.

Example 5
Electrolysis and post-treatment were carried out in the same manner as in Example 4, except that trimethylstearylammonium chloride was added so as to be 200 mg/L. Table 1 shows the production conditions, and Table 2 shows the results.

Example 6
Electrolysis and post-treatment were carried out in the same manner as in Example 4, except that trimethylstearylammonium chloride was added so as to be 50 mg/L. Table 1 shows the production conditions, and Table 2 shows the results.

Example 7
Electrolysis and post-treatment were carried out in the same manner as in Example 4, except that the concentration of sulfuric acid was 45.3 g/L. Table 1 shows the production conditions, and Table 2 shows the results.

Example 8
Electrolysis and post-treatment were carried out in the same manner as in Example 4, except that hexadecyltrimethylammonium hydroxide was added so as to be 100 mg/L. Table 1 shows the production conditions, and Table 2 shows the results.

Example 9
Electrolysis and post-treatment were carried out in the same manner as in Example 8, except that hexadecyltrimethylammonium hydroxide was added so as to be 400 mg/L. Table 1 shows the production conditions, and Table 2 shows the results.

Example 10
Electrolysis and post-treatment were carried out in the same manner as in Example 4, except that docosyltrimethylammonium sulfate was added so as to be 100 mg/L. Table 1 shows the production conditions, and Table 2 shows the results.

Example 11
Electrolysis and post-treatment were carried out in the same manner as in Example 4, except that benzyldimethylstearylammonium chloride was added so as to be 100 mg/L. Table 1 shows the production conditions, and Table 2 shows the results.

Comparative example 1
Electrolysis and post-treatment were carried out in the same manner as in Example 1, except that no surfactant was added. Table 1 shows the production conditions, and Table 2 shows the results.

Comparative example 2
Electrolysis and post-treatment were carried out in the same manner as in Example 4, except that no surfactant was added. Table 1 shows the production conditions, and Table 2 shows the results.

Comparative example 3
Electrolysis and post-treatment were carried out in the same manner as in Example 4, except that sodium dodecyl sulfate, which is an anionic surfactant, was added so as to be 100 mg/L. Table 1 shows the production conditions, and Table 2 shows the results.

Comparative example 4
Electrolysis and post-treatment were carried out in the same manner as in Example 4, except that N-dodecylbetaine, an amphoteric surfactant, was added to 100 mg/L. Table 1 shows the production conditions, and Table 2 shows the results.

Comparative example 5
Electrolysis and post-treatment were carried out in the same manner as in Example 4 except that nonionic polyethylene glycol monostearate (n=25) was added to 100 mg/L. Table 1 shows the production conditions, and Table 2 shows the results.

Comparative example 6
Electrolysis and post-treatment were carried out in the same manner as in Example 7 except that no surfactant was added, the current density was 0.34 A/dm ² and the electrolysis temperature was 97°C. Table 1 shows the production conditions, and Table 2 shows the results.

From the comparison of Examples 1 to 3 and Comparative Example 1 in Tables 1 and 2, and the comparison of Examples 4 to 11 and Comparative Example 2, a cationic surfactant was mixed in the electrolytic solution and electrodeposited at 98 ° C. or less. It was found that, by adding a surfactant, an electrolytic manganese dioxide having a smaller half-value width of the (110) plane can be obtained than when the surfactant is not mixed. Further, from a comparison between Example 7 and Comparative Example 6, it was found that electrolytic manganese dioxide with a high current density, that is, high productivity and a small half-value width of the (110) plane was obtained by electrodeposition by mixing a cationic surfactant. found to be obtainable.

Since the electrolytic manganese dioxide of the present invention has high crystallinity and low structural water content, it is suitably used as a positive electrode material with high performance and good storage characteristics as a positive electrode active material for batteries, particularly alkaline manganese dry batteries and lithium ion primary batteries. The method for producing electrolytic manganese dioxide of the present invention is a positive electrode active material for alkaline manganese dry batteries and lithium ion primary batteries, which are expected to be excellent in high discharge characteristics, especially high rate discharge characteristics. Density can be manufactured.

Claims (7)

The half width of the (110) plane in XRD measurement using a CuKα ray as a light source is 1.4 ° or more and 2.5 ° or less, and the structural water content calculated from the weight loss at 240 ° C. is 1.4 wt% or more and 2.1 wt%. Electrolytic manganese dioxide characterized by having a carbon weight fraction of 0.02 wt % or more and 1.0 wt % or less. A method of producing manganese dioxide by electrolysis in an aqueous manganese salt solution, in which a cationic surfactant is mixed in the electrolytic solution (excluding those in which a carbon material (acetylene black, ketchin black) is mixed in the electrolytic solution) 2. The method for producing electrolytic manganese dioxide according to claim 1, wherein the electrolytic deposition is performed at 98° C. or lower. 3. The method for producing electrolytic manganese dioxide according to claim 2, wherein the cationic surfactant is at least one of an alkylamine, an alkylamine salt and a quaternary ammonium salt. 4. The method for producing electrolytic manganese dioxide according to claim 2, wherein the cationic surfactant has 20 or more carbon atoms in total. The method for producing electrolytic manganese dioxide according to any one of claims 2 to 4, wherein the cationic surfactant contains one or more alkyl groups having 17 or more carbon atoms. A positive electrode active material for a battery, comprising the electrolytic manganese dioxide according to claim 1 . A battery comprising the positive electrode active material for a battery according to claim 6 .

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