ELECTROLYTIC MANGANESE DIOXIDE, METHOD FOR PRODUCING SAME, AND USE OF SAME
20210336256 · 2021-10-28
Assignee
Inventors
Cpc classification
C01P2004/61
CHEMISTRY; METALLURGY
H01M6/06
ELECTRICITY
Y02E60/10
GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
H01M2004/021
ELECTRICITY
C01P2004/51
CHEMISTRY; METALLURGY
International classification
Abstract
To provide electrolytic manganese dioxide excellent in low rate characteristics and middle rate characteristics when used as a cathode material for alkaline manganese dry cells, and a method for its production.
Electrolytic manganese dioxide of which the apparent density is at least 4.0 g/cm.sup.3 and at most 4.3 g/cm.sup.3, and the mode particle size is at least 30 μm and at most 100 μm; a method for its production and its application.
Claims
1. Electrolytic manganese dioxide, characterized in that the apparent density is at least 4.0 g/cm.sup.3 and at most 4.3 g/cm.sup.3, and the mode particle size is at least 30 μm and at most 100 μm.
2. The electrolytic manganese dioxide according to claim 1, characterized in that the micropore volume is at most 0.009 mL/g.
3. The electrolytic manganese dioxide according to claim 1 or 2, characterized in that the maximum particle size is at most 500 μm.
4. The electrolytic manganese dioxide according to claim 1, characterized in that the alkali potential is at least 280 mV and at most 350 mV.
5. The electrolytic manganese dioxide according to claim 1, characterized in that the sulfate group (SO.sub.4) content is at most 1.5 wt %.
6. The electrolytic manganese dioxide according to claim 1, characterized in that the sodium content is at least 10 wt ppm and at most 5,000 wt ppm.
7. A method for producing the electrolytic manganese dioxide as defined in claim 1, characterized in that the sulfuric acid concentration in the electrolyte at the time of electrolysis is at least 42 g/L and at most 50 g/L, the sulfuric acid concentration from the initiation of electrolysis to the completion of electrolysis is constant, the manganese/sulfuric acid concentration ratio in the electrolyte at the time of electrolysis is at least 0.1 and at most 0.6, and the electrolysis current density is at least 0.1 A/dm.sup.2 and at most 0.5 A/dm.sup.2.
8. A cathode active material for a dry cell, characterized by comprising the electrolytic manganese dioxide as defined in claim 1.
9. A dry cell characterized by comprising the cathode active material for a dry cell as defined in claim 8.
Description
BRIEF DESCRIPTION OF DRAWINGS
[0033]
[0034]
[0035]
[0036]
[0037]
EXAMPLES
[0038] Now, the present invention will be described in further detail with reference to Examples and Comparative Examples, but the present invention is by no means limited by these Examples.
[0039] <Measurement of Apparent Density, Particle Density, Open Pore Volume, Micropore Volume and Micropore Area>
[0040] The apparent density of electrolytic manganese dioxide was measured as follows.
[0041] First, the particle density of electrolytic manganese dioxide was measured using a dry automatic densimeter (AccuPyc II 1340, trade name, manufactured by Shimadzu Corporation) with helium. From the inverse of the obtained particle density, the sum of the net volume of electrolytic manganese dioxide solid and the volume of closed pores into which gas cannot infiltrate was obtained.
[0042] Then, the volume of open pores (pore size: 0.4 to 100 nm) which are open to the surface of the electrolytic manganese dioxide particles and into which gas can infiltrate, was measured by high precision multi-sample gas adsorption amount measuring apparatus (Autosorb-iQ, trade name, manufactured by Anton Paar). The electrolytic manganese dioxide particles were dehydrated at 150° C. for 4 hours while being evacuated of air, and then using argon as the adsorbent, the argon adsorption amount was measured at 87 K within a pressure range of from 0.0001 to 760 Torr, and the argon adsorption amount was taken as the volume of open pores. Further, NLDFT was applied to the obtained adsorption isotherm to calculate the pore distribution, and the pore volume and the pore area of pores within a range of from 0.46 to 1.95 nm were respectively taken as the micropore volume and the micropore area. In NLDFT, fitting was conducted using a zeolite/silica cylindrical pore model. When the volume of open pores was measured, in order to exclude the volume of pores among the electrolytic manganese dioxide particles, particles of 5 μm or smaller were removed by wet classification and the particle size was adjusted to be form 5 to 200 μm.
[0043] The apparent density (g/cm.sup.3) of electrolytic manganese dioxide was obtained from the following formula.
1/(the net volume of electrolytic manganese dioxide solid+the volume of closed pores into which gas cannot infiltrate+the volume of open pores into which gas can infiltrate)
[0044] <Measurement of Cathode Mixture Density (Packing Density)>
[0045] The cathode mixture density was measured as follows.
[0046] 65 g of electrolytic manganese dioxide, 2.9 g of graphite and 5.1 g of a 37 wt % aqueous potassium hydroxide solution were mixed by a V mixer (VM-2, trade name, manufactured by TSUTSUI SCIENTIFIC INSTRUMENTS. CO., LTD.) for 20 minutes, calendered by a roller compactor under a pressure of 30 MPa, and further classified by a sieve into 180 μm to 1 mm to obtain cathode mixture granules. 3.5 g of the cathode mixture granules were pressurized by a mold having an outer diameter of 13 mm and an inner diameter of 9 mm under 2.7 t/cm.sup.2 to prepare a ring-shaped molded product, and the density of the molded product was obtained from the weight and the volume. 18 Such ring-shaped molded products were prepared and their densities were measured, and the average was taken as the cathode mixture density.
[0047] <Measurement of Alkali Potential>
[0048] The alkali potential of electrolytic manganese dioxide was measured in a 40 wt % aqueous KOH solution as follows.
[0049] To 3 g of the electrolytic manganese dioxide, 0.9 g of graphite as a conductive agent was added to obtain a mixed powder, and 4 ml of a 40 wt % aqueous KOH solution was added to this mixed powder, to obtain a mixture slurry of the electrolytic manganese dioxide, carbon and the aqueous KOH solution. The potential of the mixture slurry was measured, based on the mercury/mercury oxide reference electrode, and the obtained value was taken as the alkali potential of the electrolytic manganese dioxide.
[0050] <Measurement of Sulfate Group and Sodium Contents>
[0051] The sulfate group and sodium contents in the electrolytic manganese dioxide were quantitatively measured by dissolving the electrolytic manganese dioxide in nitric acid and hydrogen peroxide and measuring the obtained solution by ICP.
[0052] <Measurement of Mode Particle Size, Average Particle Size and Maximum Particle Size>
[0053] The mode particle size, the average particle size (50% size) and the maximum particle size of the electrolytic manganese dioxide were measured by a particle size distribution measuring apparatus (Microtrac MT3300EXII, trade name, manufactured by MicrotracBEL Corp.) at HRA mode. No dispersion treatment such as ultrasonic dispersion was conducted at the time of measurement.
[0054] <Measurement of BET Specific Surface Area>
[0055] The BET specific surface area of the electrolytic manganese dioxide was measured by nitrogen adsorption by a BET one point method. As the measuring apparatus, a gas adsorption specific surface area measuring apparatus (Flow Sorb III, trade name, manufactured by Shimadzu Corporation) was used. Prior to the measurement, the electrolytic manganese dioxide was dehydrated by heating at 150° C. for 1 hour.
Example 1
[0056] Electrolysis was conducted by using an electrolytic cell which has a heating device, and a titanium plate as an anode and a graphite plate as a cathode, which are suspended so as to face each other.
[0057] By supplying a manganese sulfate feed solution with a manganese ion concentration of 35 g/L to the electrolytic cell, maintaining the electrolysis current density to be 0.34 A/dm.sup.2 and the temperature of the electrolytic cell to be 97° C., and adjusting the sulfuric acid concentration to be 43 g/L and the manganese/sulfuric acid concentration ratio to be 0.34, electrolysis was conducted for 15 days.
[0058] After the electrolysis, the electrodeposited plate-shaped electrolytic manganese dioxide was washed with pure water and then milled to obtain a milled product of the electrolytic manganese dioxide. Then, this electrolytic manganese dioxide milled product was put in a water bath and stirred, and an aqueous sodium hydroxide solution was added, to conduct a neutralization treatment so as to bring the pH of the slurry to be 2.8. Then, the electrolytic manganese dioxide was washed with water, filtered for separation and dried, and subjected to a sieve with an opening of 63 μm to obtain an electrolytic manganese dioxide powder. Of the obtained electrolytic manganese dioxide powder, the particle size distribution is shown in
[0059] Further, from the obtained electrolytic manganese dioxide powder, particles of 5 μm or smaller were removed as follows. First, pure water was added to the electrolytic manganese dioxide powder to prepare a slurry, to which aqueous ammonia was added to adjust the pH to be 8.5. Then, the slurry was subjected to ultrasonic dispersion and left at rest for 1 hour, and the supernatant liquid containing particles of 5 μm or smaller in a large amount was removed by decantation. Pure water was added to the obtained residue to prepare a slurry, and the same operation to remove particles of 5 μm or smaller was repeatedly carried out 5 times, and the obtained residue was dried at 60° C. to obtain an electrolytic manganese dioxide powder having particles of 5 μm or smaller removed. Of the obtained electrolytic manganese dioxide powder having particles of 5 μm or smaller removed, the particle size distribution is shown in
TABLE-US-00001 TABLE 1 BET Open Mode Maximum Average Cathode specific Apparent Particle pore Micropore Micropore particle particle particle mixture Alkali surface density density volume volume area size size size density potential area SO.sub.4 Na (g/cm.sup.3) (g/cm.sup.3) (cm.sup.3/g) (mL/g) (m.sup.2/g) (μm) (μm) (μm) (g/cm.sup.3) (mV) (m.sup.2/g) (wt %) (wtppm) Ex. 1 4.11 4.48 0.0198 0.0077 50.6 48.0 148.0 37.6 3.42 312 24.0 1.05 430 Ex. 2 4.08 4.48 0.0216 0.0067 44.0 40.4 209.3 25.5 3.44 286 24.3 1.25 1300 Ex. 3 4.01 4.47 0.0254 0.0088 58.3 44.0 148.0 32.2 3.37 296 29.3 1.13 2280 Ex. 4 4.08 4.48 0.0217 0.0074 49.2 44.0 176.0 31.5 3.43 296 24.3 1.15 2340 Ex. 5 4.05 4.48 0.0239 0.0082 54.2 40.4 148.0 32.6 3.36 312 26.3 1.20 1340 Ex. 6 4.05 4.48 0.0239 0.0082 54.2 48.0 176.0 39.4 3.39 312 26.3 1.20 1200 Ex. 7 4.05 4.48 0.0239 0.0082 54.2 57.9 248.9 52.9 3.43 312 26.3 1.20 1200 Comp. 3.92 4.49 0.0323 0.0108 70.7 40.4 148.0 33.1 3.32 315 35.6 1.16 450 Ex. 1 Comp. 3.88 4.48 0.0345 0.0158 94.0 28.5 169.4 24.1 3.27 317 38.0 1.10 1100 Ex. 2 Comp. 3.78 4.48 0.0411 0.0186 110.5 40.4 148.0 34.1 3.23 318 45.0 1.08 1010 Ex. 3
Example 2
[0060] Electrolysis was conducted in the same manner as in Example 1 except that a manganese sulfate feed solution with a manganese ion concentration of 45 g/L was supplied, that the sulfuric acid concentration was 46 g/L, that the manganese/sulfuric acid concentration ratio was 0.50, and that the pH at the time of the neutralization treatment was 4.2. Of the obtained electrolytic manganese dioxide, the results of evaluation of the apparent density, the mode particle size, etc. are shown in Table 1.
Example 3
[0061] Electrolysis was conducted in the same manner as in Example 2 except that the electrolysis current density was 0.50 A/dm.sup.2, that the temperature of the electrolytic cell was kept at 96° C., and that the pH at the time of the neutralization treatment was 5.6. Of the obtained electrolytic manganese dioxide, the results of evaluation of the apparent density, the mode particle size, etc. are shown in Table 1.
Example 4
[0062] Electrolysis was conducted in the same manner as in Example 2 except that the sulfuric acid concentration was 45 g/L, that the temperature of the electrolytic cell was kept at 96° C., and that the pH at the time of the neutralization treatment was 5.6. Of the obtained electrolytic manganese dioxide, the results of evaluation of the apparent density, the mode particle size, etc. are shown in Table 1.
Example 5
[0063] Electrolysis was conducted in the same manner as in Example 1 except that the sulfuric acid concentration was 42 g/L, that the manganese/sulfuric acid concentration ratio was 0.38, that the electrolysis current density was 0.40 A/dm.sup.2, that the temperature of the electrolytic cell was kept at 96° C., and that the pH at the time of the neutralization treatment was 4.2. Of the obtained electrolytic manganese dioxide, the results of evaluation of the apparent density, the mode particle size, etc. are shown in Table 1.
Example 6
[0064] Electrolysis was conducted in the same manner as in Example 5 except that after electrolysis, neutralization treatment, washing with water, filtration for separation and drying were conducted, the electrolytic manganese dioxide was subjected to a sieve with an opening of 75 μm. Of the obtained electrolytic manganese dioxide, the results of evaluation of the apparent density, the mode particle size, etc. are shown in Table 1.
Example 7
[0065] Electrolysis was conducted in the same manner as in Example 5 except that after electrolysis, neutralization treatment, washing with water, filtration for separation and drying were conducted, the electrolytic manganese dioxide was subjected to a sieve with an opening of 90 μm. Of the obtained electrolytic manganese dioxide, the results of evaluation of the apparent density, the mode particle size, etc. are shown in Table 1.
Comparative Example 1
[0066] Electrolysis was conducted in the same manner as in Example 2 except that the sulfuric acid concentration was 45 g/L, that the electrolysis current density was 0.55 A/dm.sup.2, that the temperature of the electrolytic cell was kept at 96° C., and that the pH at the time of the neutralization treatment was 2.8. Of the obtained electrolytic manganese dioxide, the results of evaluation of the apparent density, the mode particle size, etc. are shown in Table 1.
Comparative Example 2
[0067] Electrolysis was conducted in the same manner as in Example 3 except that the sulfuric acid concentration was 35 g/L, that the manganese/sulfuric acid concentration ratio was 0.20, that the feed manganese concentration was 25 g/L, that the pH at the time of the neutralization treatment was 4.2, and that after filtration for separation and drying, the electrolytic manganese dioxide was subjected to a sieve with an opening of 32 μm. Of the obtained electrolytic manganese dioxide, the results of evaluation of the apparent density, the mode particle size, etc. are shown in Table 1.
Comparative Example 3
[0068] Electrolysis was conducted in the same manner as in Example 3 except that the sulfuric acid concentration was 60 g/L, that the manganese/sulfuric acid concentration ratio was 0.31, that the feed manganese concentration was 50 g/L, and that the pH at the time of the neutralization treatment was 4.2. Of the obtained electrolytic manganese dioxide, the results of evaluation of the apparent density, the mode particle size, etc. are shown in Table 1.
[0069] It is found from Table 1 that by producing electrolytic manganese dioxide at a sulfuric acid concentration in each of Examples 1 to 7, the obtained electrolytic manganese dioxide has a higher apparent density, a larger mode particle size, a smaller micropore volume and a higher alkali potential as compared with Comparative Examples 1 to 3. Further, the electrolytic manganese dioxide in each of Examples 1 to 7 achieves a higher cathode mixture density and a higher alkali potential as compared with Comparative Examples 1 to 3, whereby excellent discharge characteristics particularly low rate and middle rate characteristics can be expected.
[0070] The entire disclosure of Japanese Patent Application No. 2018-160407 filed on Aug. 29, 2018 including specification, claims, drawings and summary is incorporated herein by reference in its entirety.
INDUSTRIAL APPLICABILITY
[0071] Since the electrolytic manganese dioxide of the present invention has specific apparent density and mode particle size, it is useful as a cathode active material for manganese dry cells, in particular alkaline manganese dry cells, excellent in discharge characteristics particularly low rate and middle rate discharge characteristics.