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

Abstract

Provided are: an electrolytic manganese dioxide having excellent high load discharge characteristics and capacity when used as a positive electrode material for an alkaline manganese dry battery; and a method for producing the electrolytic manganese dioxide. An electrolytic manganese dioxide having an alkaline potential of 290 mV or more and less than 350 mV, a manganese content in a dry state of 60.3% by mass or more and 63.0% by mass or less, a structural water volume as defined by a reduction in mass from 110 DEG C to 240 DEG C of 2.60% by mass or more, and a total structural water volume of 4.10% by mass or more, and a method for producing the electrolytic manganese dioxide.

Description

Technical Field

[0001] The present invention relates to electrolytic manganese dioxide, a method for manufacturing the same, and uses thereof. More specifically, the present invention relates to, for example, electrolytic manganese dioxide used as a positive electrode active material in manganese dry batteries, particularly alkaline manganese dry batteries, and a method for manufacturing the same. Background Art

[0002] Manganese dioxide is known, for example, as a positive electrode active material in manganese dry batteries, particularly alkaline manganese dry batteries, and has the advantages of excellent storage properties and low cost. In particular, alkaline manganese dry batteries using electrolytic manganese dioxide as the positive electrode active material have excellent discharge characteristics under a wide range of loads, and are therefore widely used in electronic cameras, portable information devices, and game machines and toys, and further performance improvement is desired.

[0003] Heretofore, in order to improve the high-load characteristics of alkaline manganese dry batteries, there has been proposed: an electrolytic manganese dioxide characterized in that the half-peak width of the (110) plane obtained by XRD measurement using CuK α rays as a light source is 1.8° or more and less than 2.2°, and the peak intensity ratio of the X-ray diffraction peaks (110) / (021) is 0.70 or more and 1.00 or less, and the JIS-pH (JIS K1467 5.9: pH value) is 1.5 or more and less than 5.0 (Patent Document 1); an electrolytic manganese dioxide having a high potential (hereinafter referred to as an alkaline potential) when measured in a 40 wt% KOH aqueous solution with a mercury / mercuric oxide reference electrode (Patent Documents 2 to 4); an electrolytic manganese dioxide having an average mesopore diameter of 6.5 nm or more and 10 nm or less (Patent Document 5); and an electrolytic manganese dioxide having a large amount of structural water (Patent Document 6).

[0004] The structural water that dissociates from the electrolytic manganese dioxide at 220 to 240°C has a great influence on the crystal structure (Non-Patent Document 1).

[0005] In electrolytic manganese dioxide, there are impurities such as manganese having a low valence that are ineffective as an oxidizing agent. In "JIS K 1467 (Electrolytic Manganese Dioxide for Batteries) 3. Quality", the amount of substances effective as an oxidizing agent in electrolytic manganese dioxide for batteries is specified. That is, the larger the amount of substances effective as the oxidizing agent, the larger the capacity of the positive electrode material in the battery.

[0006] As a high-load electrolytic manganese dioxide, for example, an electrolytic manganese dioxide obtained by controlling electrolysis conditions such as the sulfuric acid concentration of the electrolyte has been proposed (Patent Document 2), but in electrolysis under manufacturing conditions with a high sulfuric acid concentration in the electrolyte, the electrolytic manganese dioxide electrodeposited during electrolysis falls off from the electrolysis electrode, and stable manufacturing cannot be performed.

[0007] Therefore, as a countermeasure against the detachment of the electrolytic electrode, a method has been proposed in which the sulfuric acid concentration of the electrolytic solution at the start of electrolysis is reduced and the sulfuric acid concentration is increased during electrolysis (Patent Documents 4 to 5).

[0008] Prior Art Documents Patent Documents Patent Document 1: Japanese Patent No. 6862763 Patent Document 2: Japanese Patent No. 4827501 Patent Document 3: U.S. Patent No. 6527941 Patent Document 4: Japanese Patent No. 5428163 Patent Document 5: Japanese Unexamined Patent Application Publication No. 2021-39930 Patent Document 6: Japanese Patent No. 5136004 Non-Patent Documents Non-Patent Document 1: Tosoh Research & Technical Report, Vol. 49, No. 86, p. 21 Summary of the Invention Technical Problem to be Solved by the Invention According to the methods of Patent Documents 4 and 5, even when the sulfuric acid concentration of the electrolytic solution is high, electrolytic manganese dioxide is not easily detached, but the detailed detachment conditions of electrolytic manganese dioxide are not clear, and there is room for improvement in high-load characteristics.

[0009] The high-load characteristics of electrolytic manganese dioxide having the features described in Patent Documents 1 to 4 and Patent Document 6 are insufficient. In addition, due to the manufacturing method using sulfuric acid treatment in Patent Document 6, the remaining sulfuric acid may cause corrosion of the battery can inside the battery.

[0010] Although the electrolytic manganese dioxide of Patent Document 5 has good high-load characteristics, the amount of the substance effective as the oxidant is small.

[0011] An object of the present invention is to provide electrolytic manganese dioxide that contains a certain amount or more of manganese, has a large amount of structural water defined by mass reduction from 110°C to 240°C, and does not detach during electrolysis, and is used as a positive electrode active material for manganese dry batteries and alkaline manganese dry batteries having excellent battery performance, particularly excellent high-load characteristics and large capacity, and a method for manufacturing the electrolytic manganese dioxide.

[0012] Technical Solution for Solving the Technical Problem In the present invention, electrolytic manganese dioxide used as a positive electrode active material for manganese dry batteries, particularly alkaline manganese dry batteries, has been repeatedly studied. As a result, it has been found that by making the manganese content in the dry state a certain content, the effective oxygen in manganese dioxide increases, and by making the amount of structural water and total structural water defined by the mass reduction from 110 °C to 240 °C within a certain range, the high-load characteristics become good.

[0013] That is, as shown in the claims of the present invention, the gist of the present invention is as follows.

[0014] [1] An electrolytic manganese dioxide having an alkaline potential of 290 mV or more and less than 350 mV, a manganese content in the dry state of 60.3% by mass or more and 63.0% by mass or less, a structural water amount defined by the mass reduction from 110 °C to 240 °C of 2.60% by mass or more, and a total structural water amount of 4.10% by mass or more.

[0015] [2] The electrolytic manganese dioxide according to [1] above, wherein the alkaline potential exceeds 310 mV.

[0016] [3] The electrolytic manganese dioxide according to [1] or [2] above, wherein the content of sulfate (SO 4 ) is 1.5% by mass or less.

[0017] [4] The electrolytic manganese dioxide according to any one of [1] to [3] above, wherein the sodium content is 10 mass ppm or more and 5000 mass ppm or less.

[0018] [5] A method for manufacturing the electrolytic manganese dioxide according to any one of [1] to [4] above, which is an electrolysis method in which when the current density during electrolysis is set to J (A / dm 2 ), the ratio of the square of the manganese ion concentration [Mn 2+ (mol / L) and the hydrogen ion concentration [H + (mol / L) in the electrolyte is set to X, [Mn 2+ at the end of electrolysis is less than [Mn 2+ at the start of electrolysis, and there exists a period satisfying both of the following formulas (1) and (2) for more than 6 days.

[0019] When X = [Mn 2+ / [H + 2 , J ≤ X + 0.22 (1) X / J 2 ≤ 2.10 (2) ​[6]The manufacturing method of electrolytic manganese dioxide according to [5] above, wherein the electrolyte is a mixed solution of manganese sulfate and sulfuric acid.

[0020] [7]The manufacturing method of electrolytic manganese dioxide according to [5] or [6] above, wherein the manganese ion concentration at the start of electrolysis is 25 g / L or more.

[0021] [8]A positive electrode active material for a battery, which contains the electrolytic manganese dioxide according to any one of [1] to [4] above.

[0022] Advantages of the Invention According to the present invention, compared with conventional electrolytic manganese dioxide, it is possible to provide electrolytic manganese dioxide with good high-load characteristics. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a graph of J versus X for all examples and comparative examples.

[0024] Figure 2 It is a graph of potential versus X / J for all examples and Comparative Examples 1 to 5 2 of. DETAILED DESCRIPTION OF THE INVENTION

[0025] Hereinafter, an example of an embodiment will be shown and described for the present invention. In addition, in the present invention, each component and parameter disclosed in this specification include any combination, and in addition, the range of any combination of the upper limit and the lower limit of the values disclosed in this specification is also included in the present invention. The main terms in this embodiment are as follows.

[0026] The alkaline potential of the electrolytic manganese dioxide in this embodiment is 290 mV or more and less than 350 mV. If the alkaline potential is lower than 290 mV, the battery performance, particularly the high-load discharge characteristics, become low. If it is 350 mV or more, the output of the battery becomes high, but the cycle characteristics of the battery become low. The alkaline potential is preferably more than 310 mV and less than 350 mV, more preferably 320 mV or more and less than 350 mV, and further preferably 330 mV or more and less than 350 mV.

[0027] The manganese content of the electrolytic manganese dioxide in this embodiment is 60.3% by mass or more and 63.0% by mass or less in the dry state. If the manganese content is less than 60.3% by mass, the crystal structure is distorted in an unfavorable direction. As a result, the proportion that effectively functions as an oxidizing agent, that is, the proportion of the substance defined as manganese dioxide in the electrolytic manganese dioxide for batteries specified in "JIS K 1467 3. Quality" (hereinafter, also referred to as "MnO 2The "content" decreases. If the manganese content exceeds 63.0% by mass, the structural water cannot exist in the electrolytic manganese dioxide. The manganese content in the electrolytic manganese dioxide of the present embodiment in the dry state is preferably 60.3% by mass or more and 62.0% by mass or less, more preferably 60.3% by mass or more and 61.5% by mass or less.

[0028] Here, the "dry state" means a state in which the attached moisture has been removed from the electrolytic manganese dioxide of the present embodiment, and the amount of the attached moisture can be measured according to "JIS K 1467 5.3 Determination of moisture content" described in <Measurement of attached moisture content> below.

[0029] The amount of structural water (hereinafter, also referred to as "structural water amount at 240 °C") defined by the mass reduction from 110 °C to 240 °C of the electrolytic manganese dioxide of the present embodiment is 2.60% by mass or more. If the structural water amount at 240 °C is less than 2.60% by mass, the distortion of the crystal structure becomes smaller, the output decreases, and the high-load characteristics deteriorate significantly. The structural water amount at 240 °C is preferably 2.70% by mass or more, more preferably 2.80% by mass or more. In addition, since the distortion of the crystal structure increases and the structure collapses, the structural water amount at 240 °C is preferably 4.0% by mass or less. The measurement of the structural water amount at 240 °C is carried out according to <Measurement of structural water amount> described in the examples.

[0030] The total structural water amount (the structural water amount defined by the mass reduction from 110 °C to 320 °C in thermal analysis) of the electrolytic manganese dioxide of the present embodiment is 4.10% by mass or more. The structural water other than the structural water amount defined by the mass reduction at 240 °C has no influence on the output itself. However, if the total structural water amount is less than 4.10% by mass, the diffusion of protons is hindered and the discharge characteristics deteriorate. The total structural water amount is preferably 4.20% by mass or more, more preferably 4.30% by mass or more. In addition, if there is an excessive amount of structural water, the amount of manganese in the composition decreases, so the total structural water amount is preferably 5.0% by mass or less. The measurement of the total structural water amount is carried out according to <Measurement of structural water amount> described in the examples.

[0031] The measurement of the structural water amount can be carried out using a thermal analysis device (trade name: STA300, manufactured by Hitachi High-Tech Corporation) under a nitrogen flow at a heating rate of 10 °C / minute through a specified temperature program.

[0032] Specifically, it is heated to 110 °C and held for 16 hours to remove the adsorbed water. Then it is heated to 240 °C and held for 12 hours. Further, it is heated to 320 °C and held for 12 hours. Finally, the mass of the electrolytic manganese dioxide after heating to 620 °C and holding for 1 hour is taken as the final mass.

[0033] The ratio of the mass reduction from 110 °C to 240 °C to the final mass is taken as the structural water content at 240 °C (mass %), and the ratio of the mass reduction from 110 °C to 320 °C to the final mass is taken as the total structural water content (mass %).

[0034] The electrolytic manganese dioxide of the present embodiment may contain sulfate (SO 4 ), and the content of sulfate (SO 4 ) is preferably 0 mass % or more and 1.5 mass % or less. Thereby, when an alkaline manganese dry battery is manufactured, the high-load discharge characteristics are more excellent, and the quality maintaining the high storage characteristics of the dry battery can be achieved. The content of sulfate (SO 4 ) is more preferably 0 mass % or more and 1.3 mass % or less.

[0035] The sodium content of the electrolytic manganese dioxide of the present embodiment is preferably 10 mass ppm or more and 5000 mass ppm or less. Thereby, when an alkaline manganese dry battery is manufactured, the corrosiveness to metal materials such as the can body becomes lower, and the high-load discharge characteristics can be maintained. The sodium content is more preferably 10 mass ppm or more and 3000 mass ppm or less. The sodium contained in the electrolytic manganese dioxide mainly comes from sodium hydroxide used as a neutralizing agent.

[0036] The contents (mass %) of sulfate (SO 4 ) and sodium in the electrolytic manganese dioxide of the present embodiment are determined by ICP measurement using a conventional ICP device (for example, device name: OPTIMA3000DV, manufactured by PERKIN ELMER). In addition, the content (mass %) of SO 4 is the ratio of the mass obtained by converting the S element contained in the electrolytic manganese dioxide into SO 4 to the mass of the electrolytic manganese dioxide, and can be obtained by multiplying the concentration (mass %) of the S element obtained by ICP measurement by SO 4 / S (atomic weight ratio) for SO 4 conversion.

[0037] The full width at half maximum of the (110) plane based on XRD measurement of the electrolytic manganese dioxide of the present embodiment (hereinafter, also simply referred to as "full width at half maximum") is preferably 2.00 ° or more and 2.31 ° or less, and more preferably 2.05 ° or more and less than 2.20 °. If the full width at half maximum is within this range, it becomes a suitable crystalline state for improving the output characteristics.

[0038] The full width at half maximum can be measured by the method described in <Measurement of Full Width at Half Maximum Based on XRD> of the examples. That is, using a measuring device (for example, Ultima IV, manufactured by Rigaku Corporation), the measurement is carried out under the following conditions to obtain a powder X-ray diffraction pattern (XRD pattern).

[0039] Target (light source): CuK α (λ = 1.5418 Å) Output: 1.6 kW (40 mA - 40 kV) Filter: K β Filter Divergence slit: 1° Divergence longitudinal limiting slit: 10 mm Scattering slit: Released Receiving slit: Released Scanning mode: Continuous Scanning speed: 4.000° / min Sampling width: 0.04° (2 θ / θ ) Integration times: 1 time Measurement range: 10 - 90° (2θ / θ) The obtained XRD pattern (XRD data) is analyzed using analysis software (for example, PDXL2), and the XRD peak having a peak top at 2 θ = 22 ± 1° is regarded as the peak of the (110) plane, and its integral width is obtained. By subtracting the full width at half maximum of the standard substance ( α Type quartz powder, manufactured by NIST) from the obtained integral width, the device error is corrected, and the obtained value can be used as the full width at half maximum.

[0040] Next, the manufacturing method of electrolytic manganese dioxide of the present embodiment will be described.

[0041] In the manufacturing method of electrolytic manganese dioxide of the present embodiment, while adjusting so that the concentration of manganese ions in the electrolytic solution at the end of electrolysis is lower than the concentration of manganese ions in the electrolytic solution at the start of electrolysis, while setting the current density during electrolysis as J (A / dm 2 ), and setting the square ratio of the manganese ion concentration [Mn 2+ (mol / L) and the hydrogen ion concentration [H + (mol / L) in the electrolytic solution as X (that is, X = [Mn 2+ / [H + 2 ), the electrolyte composition and the current density are adjusted in such a way that both of the following relational expressions 1) and 2) are satisfied for a period exceeding 6 days.

[0042] ​J ≤ X + 0.22 1) X / J 2 ≤ 2.10 2) In other words, the method for manufacturing electrolytic manganese dioxide according to the present embodiment is a method for manufacturing electrolytic manganese dioxide in which the concentration of manganese ions in the electrolytic solution at the end of electrolysis is lower than that at the start of electrolysis, and the period satisfying the relational expressions 1) and 2) exceeds 6 days.

[0043] J ≤ X + 0.22 1) X / J 2 ≤ 2.10 2) In the relational expressions 1) and 2), J is the current density (A / dm 2 ), and X is the ratio of the concentration of manganese ions [Mn 2+ (mol / L) in the electrolytic solution to the square of the concentration of hydrogen ions [H + (mol / L).

[0044] Thus, it is possible to manufacture electrolytic manganese dioxide with an alkaline potential of 290 mV or more and less than 350 mV, a manganese ratio in the dry state of 60.3 mass% or more and 63.0 mass% or less, a structural water content at 240 °C of 2.60 mass% or more and a total structural water content of 4.10 mass% or more without detachment from the electrode. When the relational expression 1) is not satisfied (i.e., J ≤ X + 0.22), electrolytic manganese dioxide detaches from the electrode during electrolysis, hindering the manufacturing process. When the relational expression 2) is not satisfied (i.e., X / J 2 ≤ 2.10), the potential of electrolytic manganese dioxide decreases, and the high-load characteristics deteriorate. By adjusting the concentration of manganese ions in the electrolytic solution to be lower at the end of electrolysis than at the start of electrolysis (the concentration of manganese ions in the electrolytic solution at the end of electrolysis is lower than that in the electrolytic solution at the start of electrolysis), it is possible to increase the manganese content in electrolytic manganese dioxide.

[0045] It is preferable to use a sulfuric acid - manganese sulfate mixed solution as the electrolytic solution in the electrolytic cell.

[0046] The method for manufacturing electrolytic manganese dioxide according to the present embodiment is not particularly limited as long as the current density, the concentration of manganese ions, and the concentration of hydrogen ions during the above electrolysis satisfy the relational expressions 1) and 2). In order to improve the current efficiency during electrolysis, the temperature of the electrolytic solution is preferably 80 °C or more and 98 °C or less, and more preferably 95 °C or more and 98 °C or less.

[0047] It is preferable to use an aqueous manganese sulfate solution as the electrolytic replenishing solution.

[0048] The method for adjusting the composition of the electrolytic solution using the electrolytic replenishing solution in the method for manufacturing electrolytic manganese dioxide according to the present embodiment is not particularly limited. For example, it can be carried out by replenishing an aqueous manganese sulfate solution (electrolytic replenishing solution) and extracting the electrolytic solution. That is, through electrolysis, manganese ions in the electrolytic solution are precipitated as electrolytic manganese dioxide. As a result, the concentration of sulfate ions in the electrolytic solution becomes high. By replenishing the electrolytic replenishing solution in the electrolytic solution, the concentration of manganese ions in the electrolytic solution becomes high. As a result, electrolytic manganese dioxide can be continuously manufactured. Therefore, by controlling the replenishment of the electrolytic replenishing solution and the extraction of the electrolytic solution in such a way that the amount of manganese ions consumed due to the precipitation of electrolytic manganese dioxide is more than the amount of manganese ions supplied by the electrolytic replenishing solution, the composition of the electrolytic solution can be adjusted so that the concentration of manganese ions in the electrolytic solution at the end of electrolysis is lower than that at the start of electrolysis.

[0049] The current density during electrolysis in the method for manufacturing electrolytic manganese dioxide according to the present embodiment is not particularly limited. For example, it is preferably set to 0.2 A / dm 2 or more and 0.7 A / dm 2 or less, and more preferably set to 0.3 A / dm 2 or more and 0.6 A / dm 2 or less.

[0050] The method for manufacturing electrolytic manganese dioxide according to the present embodiment is not particularly limited as long as the current density, the concentration of manganese ions, and the concentration of hydrogen ions during the above electrolysis satisfy the relational expressions (1) and (2). Since it is a manufacturing method in which the concentration of manganese ions is reduced during electrolysis, a certain amount of manganese ions needs to be present in the electrolytic solution at the start of electrolysis. For example, the concentration of manganese ions at the start of electrolysis is preferably 25 g / L or more and 50 g / L or less.

[0051] In the method for manufacturing electrolytic manganese dioxide of the present invention, a step of pulverizing the electrolytic manganese dioxide obtained by electrolysis may be included.

[0052] Pulverization can be carried out using, for example, a roll mill, a jet mill, or the like.

[0053] Examples of roll mills include a centrifugal roll mill, a vertical Loesche mill, and the like. Among roll mills, since they are excellent in terms of cost and durability and are suitable for industrial use, a roll mill that can preferably pulverize a raw material having a micro-Vickers hardness of 400 HV (JIS Z 2244) or more and has a mill motor of 20 kW or more and 150 kW or less is preferred.

[0054] The method of using the electrolytic manganese dioxide of the present embodiment as the positive electrode active material of an alkaline manganese dry battery is not particularly limited as long as it is a method of mixing with additives by a known method to obtain a positive electrode mixture. For example, it is possible to prepare a mixed powder containing graphite for imparting conductivity to the electrolytic manganese dioxide (positive electrode active material) and an electrolytic solution, and form a powder molded body pressure-molded into a disk shape or a ring shape, which is used as the positive electrode mixture. The positive electrode active material, the negative electrode, the negative electrode current collector, the separator, and the electrolytic solution are placed in a positive electrode can and sealed, thereby manufacturing a battery (i.e., an alkaline manganese dry battery).

[0055] Examples Hereinafter, the present invention will be described in detail by way of examples and comparative examples, but the present invention is not limited to these examples.

[0056] <Measurement of alkaline potential> The alkaline potential of the electrolytic manganese dioxide of the present embodiment is measured in a 40 wt% KOH aqueous solution in the following manner.

[0057] 3 g of the electrolytic manganese dioxide of the present embodiment and 0.9 g of graphite as a conductive agent are added to form a mixed powder. 4 mL of a 40 wt% KOH aqueous solution is added to the mixed powder to form a mixture slurry of electrolytic manganese dioxide, graphite, and KOH aqueous solution. The potential of the mixture slurry is measured with a mercury / mercuric oxide reference electrode, and the obtained value is used as the alkaline potential of the electrolytic manganese dioxide of the present embodiment.

[0058] <Measurement of structural water content> The structural water content of the electrolytic manganese dioxide of the present embodiment is measured using a thermal analysis device (trade name: STA300, manufactured by Hitachi High-Tech Corporation) in the following manner.

[0059] The electrolytic manganese dioxide of the present embodiment is placed in the thermal analysis device. Under a nitrogen flow, the adsorbed water is removed by heating to 110 °C and holding for 16 hours. Then, it is heated to 240 °C and held for 12 hours, further heated to 320 °C and held for 12 hours, and then heated to 620 °C and held for 1 hour to remove substances that can be detached from the electrolytic manganese dioxide, which is taken as the final mass. The mass of the structural water that defines the mass reduction from 110 °C to 240 °C by the mass reduction from 110 °C to 240 °C is taken as the mass of the structural water at 240 °C, and the mass reduction from 110 °C to 320 °C is taken as the total mass of the structural water. By dividing the mass of the structural water by the final mass, the structural water content (mass%) of the electrolytic manganese dioxide of the present embodiment is obtained.

[0060] The heating rate of the thermal analysis in the measurement of the structural water content is set to 10 °C / minute. The detached substance from 240 °C to 320 °C is H2 O is confirmed by mass spectrometry of the detached substance.

[0061] The above-mentioned mass spectrometry uses a mass spectrometry device (device name: MS9610, manufactured by Bruker AXS) and is carried out by measuring the spectrum corresponding to m / z = 18.

[0062] <Measurement of the amount of attached moisture> The amount of attached moisture of the sample (electrolytic manganese dioxide) is measured in accordance with “JIS K 1467 5.3 Measurement of moisture content”.

[0063] That is, about 5 g of the test sample is measured into a flat weighing bottle, spread out in a substantially uniform thickness, and the lid is covered.

[0064] The mass measured with an analytical balance up to the digit of 0.1 mg is taken as S1 (g).

[0065] In addition, the lid is removed in a dryer maintained at 107 ± 2 °C, heated and dried for 2 hours, then the lid is covered and placed in the dryer, and naturally cooled to room temperature.

[0066] Then, the mass measured with an analytical balance up to the digit of 0.1 mg is taken as S0 (g).

[0067] The amount of attached moisture H is calculated by the following mathematical formula using the above S0 (g) and S1 (g).

[0068] Amount of attached moisture H (mass%) = (S1 - S0) / S1 × 100 <Measurement of manganese (Mn) content during drying> The manganese (Mn) content contained in the sample (electrolytic manganese dioxide) during drying (that is, when removing the above-mentioned amount of attached moisture) is determined by the following method in accordance with “JIS M 8232 5.3 Potassium permanganate titration method (potentiometric titration method)”.

[0069] 120 g of disodium phosphate dodecahydrate is dissolved in pure water to prepare a 1000 ml aqueous solution (hereinafter, also referred to as “disodium phosphate aqueous solution”).

[0070] Weigh 1 g of the sample (electrolytic manganese dioxide) and measure up to the digit of 1 mg. The weighing value at this time is taken as M (g).

[0071] Transfer the weighed sample (electrolytic manganese dioxide) to a beaker, add 30 mL of 35 mass% hydrochloric acid, and heat at 100 °C for 10 minutes.

[0072] Further add 5 mL of 60 mass% nitric acid and 10 mL of 70 mass% perchloric acid, and heat at 100 °C for 10 minutes.

[0073] Then, cool it to room temperature, add 20 mL of hydrochloric acid (1+4) to completely dissolve the sample (electrolytic manganese dioxide). Transfer all the obtained solution to a 250-mL volumetric flask and make up the volume to the mark with pure water.

[0074] Transfer 50 mL of the solution made up to the mark to a beaker, and add 250 mL of disodium phosphate solution while manually stirring. Then, using a pH meter (device name: D-51, manufactured by Horiba, Ltd.), adjust the pH to 6.5 to 7.0 while adding hydrochloric acid (1+4).

[0075] Add 20 mmol / L potassium permanganate solution to the solution after pH adjustment, and perform potentiometric titration using a potentiometer (product name: AT-610, manufactured by Kyoto Electronics Industry Co., Ltd.). The end point is the point where the change in the indicated value of the potential difference becomes the largest. Take the added amount of the potassium permanganate standard solution at the end point as V1 (mL).

[0076] Take the added amount of the potassium permanganate standard solution when the above operation is carried out without adding the sample as V2 (mL).

[0077] From the obtained V1 (mL) and V2 (mL), calculate the manganese (Mn) content in the sample (electrolytic manganese dioxide) at the time of drying using the following formula.

[0078] Manganese (Mn) content (mass %) in the sample (electrolytic manganese dioxide) =(V1-V2)×F1×0.004395 / (m1 / 5)×100×K F1: Equivalent concentration of 20 mmol / L potassium permanganate standard solution m1: Weighing value of the sample (electrolytic manganese dioxide) (g) K: Conversion factor to the dried sample = 100 / (100-attached moisture content H (mass %)) <MnO 2 Determination of content> MnO in the sample (electrolytic manganese dioxide) 2 The determination of the content is carried out by the method described below in accordance with "JIS K 1467 5.2 Manganese dioxide (MnO 2 )".

[0079] Dissolve 9.8 g of oxalic acid dihydrate in 800 mL of pure water, and further add 200 mL of sulfuric acid (1+1) to prepare an oxalic acid solution (7 g / L).

[0080] Weigh 0.25 g of the sample (electrolytic manganese dioxide) in a conical flask and add 50 mL of oxalic acid solution (7 g / L) using a whole pipette until the number of digits of 0.1 mg is measured. While keeping the liquid temperature in the flask at 60 °C, stir for 20 minutes using a magnetic stirrer while maintaining the temperature with a water bath to completely dissolve the sample (electrolytic manganese dioxide). Then, adjust the solution volume to 60 mL.

[0081] While stirring with a magnetic stirrer, titrate with 0.02 mol / L potassium permanganate solution. The end point is the moment when the light red color does not disappear for more than 30 seconds. Record the volume of potassium permanganate solution added at the end point as v1 (mL).

[0082] Record the volume of potassium permanganate solution added when performing the above operation without adding the sample as v2 (mL).

[0083] From the obtained v1 (mL) and v2 (mL), calculate the MnO 2 content (mass %) in the sample (electrolytic manganese dioxide) using the following formula.

[0084] MnO in the sample (electrolytic manganese dioxide) 2 content (mass %) =(v1 - v2) × F2 × 0.004347 / m2 × 100 × K F2: Normality of 0.02 mol / L potassium permanganate solution m2: Weight of the sample (g) K: Conversion factor to dry sample = 100 / (100 - adsorbed moisture H (mass %)) <Determination of sulfate and sodium content> The sulfate and sodium content of electrolytic manganese dioxide is determined by dissolving the sample (electrolytic manganese dioxide) in a mixed solution of nitric acid and hydrogen peroxide water, and measuring and quantifying the resulting solution using ICP (equipment name: OPTIMA3000DV, manufactured by PERKIN ELMER).

[0085] In addition, the content (mass %) of SO 4 is obtained by multiplying the concentration (mass %) of S element determined by ICP measurement by SO 4 / S (atomic weight ratio) for SO 4 conversion.

[0086] <Determination of full width at half maximum based on XRD> The full width at half maximum is measured using a powder X-ray diffractometer (product name: Ultima IV, manufactured by Rigaku), and is obtained using the above method from the XRD pattern measured under the following conditions.

[0087] · Target (X-ray source): CuK α ( λ = 1.5418 Å) · Output: 1.6 kW (40 mA - 40 kV) · Filter: K β Filter · Divergence slit: 1° · Divergence longitudinal limiting slit: 10 mm · Scattering slit: Released · Receiving slit: Released · Scanning mode: Continuous · Scanning speed: 4.000° / min · Sampling width: 0.04° (2 θ / θ ) · Number of integrations: 1 time · Measurement range: 10 - 90° (2 θ / θ ) The obtained XRD data pattern was analyzed using the analysis software (PDXL2) attached to the powder X-ray diffractometer to obtain the integrated width of the (110) plane near 2 θ = 22°.

[0088] In addition, in order to correct the error of the measuring device, a measurement of an XRD standard substance (NIST-made α type quartz powder) was performed in advance, and the full width at half maximum was obtained by subtracting the integrated width of the standard substance from the integrated width of LMO.

[0089] <Measurement of high-load discharge characteristics> The high-load discharge characteristics were measured as follows.

[0090] 65 g of the sample (electrolytic manganese dioxide), 2.9 g of graphite, and 5.1 g of 37 wt% aqueous potassium hydroxide solution were mixed using a V-type mixer (device name: VM-2, manufactured by Tsutsui Rikagaku) for 20 minutes, then rolled under a pressure of 30 MPa using a roll compactor (device name: 16-056, manufactured by Nishimura Machinery), and further sieved into oversize with a mesh of 180 μ μm and undersize with a mesh of 1 mm to obtain positive electrode mixture particles.

[0091] Using a mold with an outer diameter of 13 mm φ and an inner diameter of 9 mm φ at 2.7 t / cm 2Press 3.5 g of the positive electrode mixture particles to produce a ring-shaped molded body. After placing three ring-shaped molded bodies into the positive electrode can for a size AA dry cell, press them at 2.7 t / cm 2 to perform secondary forming.

[0092] A cylindrical separator is provided inside the positive electrode mixture that has been secondarily formed into a ring shape. 1.6 g of a 37 wt% potassium hydroxide aqueous solution is dropped onto the bottom of the dry cell and allowed to stand for 30 minutes. After injecting 6 g of a negative electrode gel in which 68 wt% Zn particles are mixed into a 37 wt% potassium hydroxide aqueous solution containing polyacrylic acid into the inside of the cylindrical separator, it is sealed with a negative electrode can equipped with a current collector rod to produce a dry cell (alkaline manganese dry cell).

[0093] After storing and allowing to stand for 7 days in a thermostat at 20°C the dry cells (alkaline manganese dry cells) using the electrolytic manganese dioxides of the examples and comparative examples, measure the number of 1.5W pulses according to the "1.5W discharge method" specified by the American National Standards Institute (ANSI). As a reference, produce the same dry cells. Take the ratio of the number of discharges of the dry cell produced using the sample (Comparative Example 4 described later) that has undergone a discharge test to the number of 1.5W pulses as the high load characteristic (that is, take the ratio of the number of 1.5W pulses of the electrolytic manganese dioxides of the examples and comparative examples to the number of 1.5W pulses of the reference (Comparative Example 4 described later) as the high load characteristic).

[0094] The number of 1.5W pulses based on the "1.5W discharge method" of the examples and comparative examples (hereinafter, also simply referred to as the "number of 1.5W pulses") is measured by the following method.

[0095] At a temperature of 20 ± 1°C, discharge one produced dry cell at 1500 mW for 2 seconds, then discharge at 650 mW for 28 seconds to perform a 30-second discharge process. Consider the above discharge process as one pattern and perform 10 patterns for a total of 5 minutes, then rest for 55 minutes. Repeat the 1-hour cycle of the discharge process and rest, and measure the number of cycles when the closed-circuit voltage of the dry cell reaches 1.05V. Measure three times and take the arithmetic mean of the three cycle numbers as the number of 1.5W pulses.

[0096] The high load characteristic (%) is represented by the following formula.

[0097] High load characteristic (%) = (Number of 1.5W pulses (times) of the examples and comparative examples) / (Number of 1.5W pulses (times) of the reference (Comparative Example 4 described later)) × 100 (Manganese ion concentration, sulfuric acid concentration, and hydrogen ion concentration) The manganese ion concentration, sulfuric acid concentration, and hydrogen ion concentration of the electrolytic solution and the electrolytic replenishing solution are determined as follows. That is, the hydrogen ion concentration and the sulfuric acid concentration are determined by neutralization titration, and the hydrogen ion concentration determined by neutralization titration and the concentration that is half of the hydrogen ion concentration are used as the sulfuric acid concentration. The manganese ion concentration is determined by ICP analysis.

[0098] Example 1 Electrolysis was carried out using an electrolytic cell having a heating device, and a titanium plate with a height of 250 mm, a width of 200 mm, and a thickness of 5 mm as the anode and a graphite plate with a height of 250 mm, a width of 200 mm, and a thickness of 10 mm as the cathode were suspended opposite to each other.

[0099] A sulfuric acid-manganese sulfate mixed aqueous solution with a hydrogen ion concentration of 0.571 mol / L and a manganese ion concentration of 0.570 mol / L was used as the electrolytic solution at the start of electrolysis. A specified amount of the electrolytic solution was charged into the electrolytic cell in such a way that the anode and the graphite plate were immersed in the electrolytic solution. With a temperature of 97 °C and an electrolysis current density (hereinafter referred to as "electrolysis current density") of 0.34 A / dm 2 electrolysis was started. As the electrolytic replenishing solution, an aqueous manganese sulfate solution with a manganese concentration of 38 g / L was used and made to flow through the electrolytic cell. As electrolytic manganese dioxide was precipitated due to electrolysis, the sulfuric acid concentration (and hydrogen ion concentration) of the electrolytic solution during electrolysis increased, while the manganese ion concentration decreased. Therefore, the electrolytic solution was appropriately sampled, and while appropriately analyzing its sulfuric acid concentration and manganese ion concentration, the supply amount of the electrolytic replenishing solution was adjusted. Five days after the start of electrolysis, it was confirmed that the hydrogen ion concentration of the electrolytic solution reached 1.16 mol / L and the manganese ion concentration reached 0.197 mol / L. Then, while maintaining this state (i.e., the state where the hydrogen ion concentration in the electrolytic solution is 1.16 mol / L and the manganese ion concentration is 0.197 mol / L) for 10 days, electrolysis was continued (total electrolysis period: 15 days).

[0100] During electrolysis, manganese dioxide did not fall off from the anode. From the sixth day to the end of electrolysis, X (i.e., the ratio of the square of the manganese ion concentration [Mn 2+ and the hydrogen ion concentration [H + (mol / L); X = [Mn 2+ / [H + 2 ) was 0.146, and as shown below, within 10 days, the relational expressions 1) and 2) were satisfied.

[0101] (0.34) ≤ (0.146) + 0.22 = (0.366) 1) (0.146) / (0.34) 2 = (1.26) ≤ 2.10 2) ​After electrolysis, the electro-deposited plate-shaped electrolytic manganese dioxide is washed with pure water and then pulverized to obtain a pulverized product of electrolytic manganese dioxide. Subsequently, the pulverized product is put into a water tank to form a slurry. While stirring, an aqueous sodium hydroxide solution is added to the slurry in such a way that the pH of the slurry becomes 4.2 and neutralization treatment is carried out. Then, after washing, filtration separation, and drying of the electrolytic manganese dioxide, it is passed through a sieve with a mesh of 63 μ m to obtain electrolytic manganese dioxide powder.

[0102] The full width at half maximum of the obtained electrolytic manganese dioxide is 2.31°.

[0103] The evaluation results of the electrolytic manganese dioxide obtained in each example are shown in the following table.

[0104] Example 2 The electrolysis current density is 0.40 A / dm 2 . An aqueous manganese sulfate solution with a manganese concentration of 43 g / L is used as the electrolysis replenishing solution. From the sixth day to the end of electrolysis, the hydrogen ion concentration of the electrolyte is 1.12 mol / L and the manganese ion concentration is 0.331 mol / L. Except for this, electrolysis is carried out in the same manner as in Example 1. It should be noted that from the sixth day to the end of electrolysis, the hydrogen ion concentration and the manganese ion concentration of the electrolyte are the same concentration.

[0105] During electrolysis, manganese dioxide did not fall off from the anode. From the sixth day to the end of electrolysis, X is 0.264. As shown below, within 10 days, the relational expressions 1) and 2) are satisfied.

[0106] (0.40) ≤ (0.264) + 0.22 = (0.484) 1) (0.264) / (0.40) 2 = (1.65) ≤ 2.10 2) The full width at half maximum of the obtained electrolytic manganese dioxide is 2.26°.

[0107] Example 3 The electrolysis current density is 0.37 A / dm 2 . Except for this, electrolysis is carried out in the same manner as in Example 2. During electrolysis, manganese dioxide did not fall off from the anode. From the sixth day to the end of electrolysis, X is 0.264. As shown below, within 10 days, the relational expressions 1) and 2) are satisfied.

[0108] (0.37) ≤ (0.264) + 0.22 = (0.484) 1) (0.264) / (0.37) 2 = (1.93) ≤ 2.10 2) The full width at half maximum of the obtained electrolytic manganese dioxide is 2.24°.

[0109] Example 4 Let the current density be 0.34 A / dm 2 , let the hydrogen ion concentration of the electrolytic solution at the start of electrolysis be 0.765 mol / L, let the manganese ion concentration be 0.501 mol / L, and conduct electrolysis. Conduct electrolysis while maintaining the liquid composition for 7 days. X at 7 days from the start of electrolysis is 0.856. As shown below, the relational expression 1) is satisfied, but the relational expression 2) is not satisfied.

[0110] (0.34) ≤ (0.856) + 0.22 = (1.08) 1) (0.856) / (0.34) 2 = (7.41) > 2.10 2) Then, while continuing electrolysis, from the eighth day to the ninth day from the start of electrolysis, use an aqueous manganese sulfate solution with a manganese concentration of 45 g / L as the electrolytic replenishing solution, and continuously change the composition of the electrolytic solution. From the ninth day from the start of electrolysis, maintain the state where the hydrogen ion concentration is 1.22 mol / L and the manganese ion concentration is 0.306 mol / L, and further conduct electrolysis for 7 days (total electrolysis period: 15 days).

[0111] During electrolysis, manganese dioxide did not fall off from the anode. X from the ninth day from the start of electrolysis to the end of electrolysis is 0.206. As shown below, during the 7 days in the second half of electrolysis, the relational expressions 1) and 2) are satisfied.

[0112] (0.34) ≤ (0.206) + 0.22 = (0.426) 1) (0.206) / (0.34) 2 = (1.78) ≤ 2.10 2) The full width at half maximum of the obtained electrolytic manganese dioxide is 2.05°.

[0113] The post-treatment after electrolysis is carried out in the same manner as in Example 1.

[0114] Example 5 Let the electrolysis current density be 0.37 A / dm 2 , and use an aqueous manganese sulfate solution with a manganese concentration of 43 g / L as the electrolytic replenishing solution. Let the hydrogen ion concentration of the electrolytic solution at the end of electrolysis be 1.22 mol / L and the manganese ion concentration be 0.273 mol / L. Except for this, conduct electrolysis using the same method as in Example 1. It should be noted that the hydrogen ion concentration and the manganese ion concentration of the electrolytic solution from the sixth day from the start of electrolysis to the end of electrolysis are the same concentration.

[0115] During electrolysis, manganese dioxide did not fall off from the anode. The value of X from the sixth day to the end of electrolysis was 0.183. As described below, within 10 days, the relational expressions 1) and 2) were satisfied.

[0116] (0.37) ≤ (0.183) + 0.22 = (0.403) 1) (0.183) / (0.37) 2 = (1.34) ≤ 2.10 2) The half-peak width of the electrolytic manganese dioxide obtained was 2.19°.

[0117] Example 6 The hydrogen ion concentration of the electrolyte at the start of electrolysis was 0.734 mol / L, the manganese ion concentration was 0.491 mol / L, and an aqueous manganese sulfate solution with a manganese concentration of 45 g / L was used as the electrolytic replenishing solution. The hydrogen ion concentration from the sixth day to the end of electrolysis was 1.12 mol / L, and the manganese ion concentration was 0.300 mol / L. Except for this, electrolysis was carried out in the same manner as in Example 1. It should be noted that the hydrogen ion concentration and the manganese ion concentration of the electrolyte from the sixth day to the end of electrolysis were the same concentration.

[0118] During electrolysis, manganese dioxide did not fall off from the anode. The value of X from the sixth day to the end of electrolysis was 0.239. As shown below, within 10 days, the relational expressions 1) and 2) were satisfied.

[0119] (0.34) ≤ (0.239) + 0.22 = (0.459) 1) (0.239) / (0.34) 2 = (2.07) ≤ 2.10 2) The half-peak width of the electrolytic manganese dioxide obtained was 2.01°.

[0120] Example 7 The electrolysis current density was 0.40 A / dm 2 , and an aqueous manganese sulfate solution with a manganese concentration of 43 g / L was used as the electrolytic replenishing solution. The hydrogen ion concentration of the electrolyte from the sixth day to the end of electrolysis was 1.18 mol / L, and the manganese ion concentration was 0.295 mol / L. Except for this, electrolysis was carried out in the same manner as in Example 1. It should be noted that the hydrogen ion concentration and the manganese ion concentration of the electrolyte from the sixth day to the end of electrolysis were the same concentration.

[0121] During electrolysis, manganese dioxide did not fall off from the anode. The value of X from the sixth day to the end of electrolysis was 0.212. As shown below, within 10 days, the relational expressions 1) and 2) were satisfied.

[0122] (0.40) ≤ (0.212) + 0.22 = (0.432) 1) (0.212) / (0.40) 2 = (1.32) ≤ 2.10 2) The full width at half maximum of the obtained electrolytic manganese dioxide is 2.23°.

[0123] Example 8 The electrolytic replenishing solution uses an aqueous manganese sulfate solution with a manganese concentration of 41 g / L, and the hydrogen ion concentration of the electrolyte solution from the sixth day to the end of electrolysis is 1.24 mol / L, and the manganese ion concentration is 0.222 mol / L. Except for this, electrolysis is carried out using the same method as in Example 1. It should be noted that the hydrogen ion concentration and the manganese ion concentration of the electrolyte solution from the sixth day to the end of electrolysis are the same concentration.

[0124] During electrolysis, manganese dioxide did not fall off from the anode. X from the sixth day to the end of electrolysis is 0.144. As shown below, within 10 days, the relational expressions 1) and 2) are satisfied.

[0125] (0.34) ≤ (0.144) + 0.22 = (0.364) 1) (0.144) / (0.34) 2 = (1.24) ≤ 2.10 2) The full width at half maximum of the obtained electrolytic manganese dioxide is 2.12°.

[0126] Example 9 The electrolytic replenishing solution uses an aqueous manganese sulfate solution with a manganese concentration of 38 g / L, and the hydrogen ion concentration of the electrolyte solution from the sixth day to the end of electrolysis is 1.16 mol / L, and the manganese ion concentration is 0.207 mol / L. Except for this, electrolysis is carried out using the same method as in Example 1. It should be noted that the hydrogen ion concentration and the manganese ion concentration of the electrolyte solution from the sixth day to the end of electrolysis are the same concentration.

[0127] During electrolysis, manganese dioxide did not fall off from the anode. X from the sixth day to the end of electrolysis is 0.154. As shown below, within 10 days, the relational expressions 1) and 2) are satisfied.

[0128] (0.34) ≤ (0.154) + 0.22 = (0.374) 1) (0.154) / (0.34) 2 = (1.33) ≤ 2.10 2) The full width at half maximum of the obtained electrolytic manganese dioxide is 2.12°.

[0129] Example 10 The electrolytic replenishing solution uses an aqueous manganese sulfate solution with a manganese concentration of 36 g / L, and the hydrogen ion concentration of the electrolyte solution from the sixth day to the end of electrolysis is 1.08 mol / L, and the manganese ion concentration is 0.193 mol / L. Except for this, electrolysis is carried out in the same manner as in Example 1. It should be noted that the hydrogen ion concentration and manganese ion concentration of the electrolyte solution from the sixth day to the end of electrolysis are the same concentration.

[0130] During electrolysis, manganese dioxide did not fall off from the anode. From the sixth day to the end of electrolysis, X is 0.165. As shown below, within 10 days, the relational expressions 1) and 2) are satisfied.

[0131] (0.34) ≤ (0.165) + 0.22 = (0.385) 1) (0.165) / (0.34) 2 = (1.43) ≤ 2.10 2) The half-peak width of the obtained electrolytic manganese dioxide is 2.14°.

[0132] Comparative Example 1 Same as Example 1 of Japanese Patent Laid-Open No. 2021-39930, the electrolytic replenishing solution is an aqueous manganese sulfate solution with a manganese concentration of 45 g / L, and the electrolytic current density is 0.34 A / dm 2 The manganese / sulfuric acid concentration ratio in the electrolyte solution is maintained at 0.25, and the sulfuric acid concentration of the electrolyte solution is 38 g / L and 63 g / L at the start and end of electrolysis respectively. The sulfuric acid concentration and manganese ion concentration of the electrolyte solution increase continuously, and electrolysis is carried out for 15 days. The temperature of the electrolyte solution is 93 °C before the sulfuric acid concentration reaches 40 g / L, and is changed to 97 °C at the moment when it reaches 40 g / L.

[0133] During electrolysis, manganese dioxide did not fall off from the anode. At this time, the manganese ion concentration of the electrolyte solution at the start of electrolysis is 0.175 mol / L, and the hydrogen ion concentration is 0.775 mol / L. From the start of electrolysis to the fifth day, the manganese ion concentration is 0.211 mol / L, and the hydrogen ion concentration is 0.943 mol / L. The X of the liquid composition is 0.237, and the relationship between X and the current density J is as follows.

[0134] (0.34) ≤ (0.237) + 0.22 = (0.457) 1) (0.237) / (0.34) 2 = (2.05) ≤ 2.10 2) At the end of electrolysis, the manganese ion concentration in the electrolyte solution is 0.286 mol / L, the hydrogen ion concentration is 1.28 mol / L, and the X of the liquid composition at the end of electrolysis is 0.175. As shown below, within 11 days from the fifth day to the fifteenth day of the start of electrolysis, equations (1) and (2) are satisfied.

[0135] (0.34) ≤ (0.175) + 0.22 = (0.395) (1) (0.175) / (0.34) 2 = (1.51) ≤ 2.10 (2) The half-peak width of the obtained electrolytic manganese dioxide is 2.30°.

[0136] Comparative Example 2 The liquid composition at the start of electrolysis (i.e., hydrogen ion concentration and manganese ion concentration) was maintained for 9 days, and the liquid composition was changed from the tenth day to the eleventh day of the start of electrolysis so that the manganese ion concentration in the changed liquid composition was 0.335 mol / L, and from the eleventh day to the fifteenth day (at the end of electrolysis) of the start of electrolysis, the changed liquid composition was maintained. Except for this, electrolysis was carried out using the same method as in Example 4.

[0137] During electrolysis, manganese dioxide did not fall off from the anode. The X for 9 days from the start of electrolysis is 0.856. As shown below, equation (1) is satisfied, but equation (2) is not satisfied.

[0138] (0.34) ≤ (0.856) + 0.22 = (1.076) (1) (0.856) / (0.34) 2 = (7.41) > 2.10 (2) The X from the eleventh day to the end of electrolysis of the start of electrolysis is 0.225. As shown below, within 5 days, equations (1) and (2) are satisfied.

[0139] (0.34) ≤ (0.225) + 0.22 = (0.445) (1) (0.25) / (0.34) 2 = (1.95) ≤ 2.10 (2) The half-peak width of the obtained electrolytic manganese dioxide is 1.94°.

[0140] Comparative Example 3 An aqueous manganese sulfate solution with a manganese concentration of 35 g / L was used as the electrolysis replenishing solution, and the hydrogen ion concentration and manganese ion concentration of the electrolyte solution from the sixth day to the end of electrolysis of the start of electrolysis were 0.958 mol / L and 0.240 mol / L, respectively. Except for this, electrolysis was carried out using the same method as in Example 1.

[0141] During electrolysis, manganese dioxide did not fall off from the anode. The value of X from the sixth day to the end of electrolysis was 0.262. As shown below, it satisfied relationship 1), but did not satisfy relationship 2).

[0142] (0.34) ≤ (0.262) + 0.22 = (0.482) 1) (0.262) / (0.34) 2 = (2.26) > 2.10 2) The half-peak width of the obtained electrolytic manganese dioxide was 2.14°.

[0143] Comparative Example 4 The hydrogen ion concentration of the electrolyte from the start of electrolysis was 0.734 mol / L, and the manganese ion concentration was 0.519 mol / L. And the hydrogen ion concentration of the electrolyte from the eleventh day to the end of electrolysis was 1.06 mol / L, and the manganese ion concentration was 0.346 mol / L. Except for this, electrolysis was carried out in the same manner as in Comparative Example 2. It should be noted that the hydrogen ion concentration and manganese ion concentration of the electrolyte from the eleventh day to the end of electrolysis were the same concentration.

[0144] During electrolysis, manganese dioxide did not fall off from the anode. The value of X for 9 days from the start of electrolysis was 0.963. As shown below, it satisfied relationship 1), but did not satisfy relationship 2).

[0145] (0.34) ≤ (0.963) + 0.22 = (1.183) 1) (0.963) / (0.34) 2 = (8.33) > 2.10 2) The value of X from the eleventh day to the end of electrolysis was 0.308. As shown below, it satisfied relationship 1), but did not satisfy relationship 2). That is, relationship 2) was not satisfied throughout the entire period.

[0146] (0.34) ≤ (0.308) + 0.22 = (0.528) 1) (0.308) / (0.34) 2 = (2.66) > 2.10 2) The half-peak width of the obtained electrolytic manganese dioxide was 2.02°.

[0147] Comparative Example 5 The hydrogen ion concentration of the electrolyte for 7 days from the start of electrolysis was 0.754 mol / L, and the manganese ion concentration was 0.491 mol / L. And the hydrogen ion concentration of the electrolyte for 7 days from the ninth day to the end of electrolysis was 0.979 mol / L, and the manganese ion concentration was 0.437 mol / L. Except for this, electrolysis was carried out in the same manner as in Example 4.

[0148] During electrolysis, manganese dioxide did not fall off from the anode. The X value for 7 days from the start of electrolysis was 0.864. As shown below, it satisfied relationship 1), but did not satisfy relationship 2).

[0149] (0.34) ≤ (0.864) + 0.22 = (1.08) 1) (0.864) / (0.34) 2 = (7.47) > 2.10 2) The X value from the ninth day to the end of electrolysis from the start of electrolysis was 0.456. As shown below, it satisfied relationship 1), but did not satisfy relationship 2). That is, relationship 2) was not satisfied throughout the entire period.

[0150] (0.34) ≤ (0.456) + 0.22 = (0.676) 1) (0.456) / (0.34) 2 = (3.94) > 2.10 2) Comparative Example 6 The electrolysis current density was made 0.37 A / dm 2 , and the hydrogen ion concentration of the electrolytic solution from the sixth day to the end of electrolysis from the start of electrolysis was 1.31 mol / L, and the manganese ion concentration was 0.233 mol / L. Except for this, electrolysis was carried out using the same method as in Example 1. It should be noted that the hydrogen ion concentration and manganese ion concentration of the electrolytic solution from the sixth day to the end of electrolysis were the same concentration.

[0151] During electrolysis, manganese dioxide fell off from the anode and could not be recovered. The X value from the sixth day to the end of electrolysis from the start of electrolysis was 0.137. As shown below, it satisfied relationship 2), but did not satisfy relationship 1).

[0152] (0.37) > (0.136) + 0.22 = (0.356) 1) (0.136) / (0.37) 2 = (0.992) ≤ 2.10 2) Comparative Example 7 The electrolysis current density was made 0.40 A / dm 2 , the electrolytic replenishing solution used an aqueous manganese sulfate solution with a manganese concentration of 33 g / L, and the hydrogen ion concentration of the electrolytic solution from the sixth day to the end of electrolysis from the start of electrolysis was 1.02 mol / L, and the manganese ion concentration was 0.173 mol / L. Except for this, electrolysis was carried out using the same method as in Example 1. It should be noted that the hydrogen ion concentration and manganese ion concentration of the electrolytic solution from the sixth day to the end of electrolysis were the same concentration.

[0153] During electrolysis, manganese dioxide falls off from the anode and cannot be recycled. The value of X from the sixth day to the end of electrolysis is 0.166. As shown below, it satisfies relation 2), but does not satisfy relation 1).

[0154] (0.40) > (0.166) + 0.22 = (0.386) 1) (0.166) / (0.40) 2 = (1.04) ≤ 2.10 2) Comparative Example 8 Set the electrolysis current density to 0.40 A / dm 2 , and perform electrolysis using the same method as in Example 1 except for this.

[0155] During electrolysis, manganese dioxide falls off from the anode and cannot be recycled. The value of X from the sixth day to the end of electrolysis is 0.146. As shown below, it satisfies relation 2), but does not satisfy relation 1).

[0156] (0.40) > (0.146) + 0.22 = (0.366) 1) (0.146) / (0.40) 2 = (0.915) ≤ 2.10 2) Comparative Example 9 Set the electrolysis current density to 0.45 A / dm 2 , and make the hydrogen ion concentration of the electrolyte from the sixth day to the end of electrolysis be 1.18 mol / L and the manganese ion concentration be 0.295 mol / L. Except for this, perform electrolysis using the same method as in Example 1. It should be noted that the hydrogen ion concentration and manganese ion concentration of the electrolyte from the sixth day to the end of electrolysis are the same concentration.

[0157] During electrolysis, manganese dioxide falls off from the anode and cannot be recycled. The value of X from the sixth day to the end of electrolysis is 0.211. As shown below, it satisfies relation 2), but does not satisfy relation 1).

[0158] (0.45) > (0.211) + 0.22 = (0.431) 1) (0.211) / (0.45) 2 = (1.05) ≤ 2.10 2) Comparative Example 10 Set the electrolysis current density to 0.45 A / dm 2 , and perform electrolysis using the same method as in Example 1 except for this. During electrolysis, manganese dioxide falls off from the anode and cannot be recycled. The value of X from the sixth day to the end of electrolysis is 0.146. As shown below, it satisfies relation 2), but does not satisfy relation 1).

[0159] (0.45) > (0.146) + 0.22 = (0.366) 1) (0.146) / (0.45) 2 = (0.723) ≤ 2.10 2) Comparative Example 11 The electrolysis current density was made 0.45 A / dm 2 , and except for this, electrolysis was carried out in the same manner as in Comparative Example 7. During electrolysis, manganese dioxide peeled off from the anode and could not be recovered. The X from the sixth day to the end of electrolysis was 0.166. As shown below, the relational expression 2) was satisfied, but the relational expression 1) was not satisfied.

[0160] (0.45) > (0.166) + 0.22 = (0.386) 1) (0.166) / (0.45) 2 = (0.821) ≤ 2.10 2) [Table 1] According to Comparative Example 1, if the electrolysis method is not such that the manganese ion concentration at the end is lower than that at the start, the manganese ratio during drying cannot reach 60.3 mass% or more. If the manganese ratio is less than 60.3 mass%, the MnO 2 content rate decreases.

[0161] According to Example 4 and Comparative Example 2, when the period during which the electrolyte composition satisfies formula (1) and formula (2) does not exceed 6 days, although the structural water amount at 240 °C increases, the total structural water amount decreases, and the high load characteristics also decrease.

[0162] According to Comparative Example 4, even if the total structural water amount is sufficient, when the structural water amount at 240 °C is small, the alkaline potential and high load characteristics decrease.

[0163] From Comparative Examples 3 to 5, it can be seen that when the electrolyte composition at the end of electrolysis does not satisfy formula (2), the structural water amount at 240 °C decreases and the high load characteristics decrease.

[0164] In Comparative Examples 6 to 11, during electrolysis, electrolytic manganese dioxide peeled off from the anode and the high load characteristics could not be measured, so they were removed from the table. When the liquid composition at the end of electrolysis does not satisfy (1), manganese dioxide peels off from the anode.

[0165] The plots of J versus X for all the examples and comparative examples are shown in Figure 1 . Taking the formula (1): J = X + 0.22 as the boundary, the peeling or non-peeling of electrolytic manganese dioxide was known.

[0166] The potentials of all the Examples and Comparative Examples 1 to 5 are relative to X / J 2 The graphs are shown in Figure 2 . When the liquid composition at the end of electrolysis does not satisfy the formula (2), the potential decreases and the high-load characteristics deteriorate.

[0167] Although the present invention has been described in detail with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the present invention.

[0168] It should be noted that the entire contents of the specification, claims, drawings, and abstract of Japanese Patent Application No. 2022-184032 filed on November 17, 2022 are incorporated herein by reference as the disclosure of the specification of the present disclosure.

[0169] Industrial Applicability The electrolytic manganese dioxide of the present invention can be used as a positive electrode active material for manganese dry batteries, particularly alkaline manganese dry batteries, which have excellent discharge performance, particularly high-load discharge characteristics and capacity, because of its specific manganese ratio and structural water content.

Claims

1. An electrolytic manganese dioxide, characterized in that, the basic potential of the electrolytic manganese dioxide is above 290 mV and less than 350 mV, the manganese content in the dry state is above 60.3% by mass and below 63.0% by mass, the structural water content defined by the mass reduction from 110 °C to 240 °C is above 2.60% by mass, and the total structural water content is above 4.10% by mass.

2. The electrolytic manganese dioxide according to claim 1, wherein, the basic potential of the electrolytic manganese dioxide exceeds 310 mV.

3. The electrolytic manganese dioxide according to claim 1 or 2, wherein, The sulfate radical, i.e., SO 4 content of the electrolytic manganese dioxide is 1.5 mass% or less.

4. The electrolytic manganese dioxide according to any one of claims 1 to 3, wherein, the sodium content of the electrolytic manganese dioxide is above 10 mass ppm and below 5000 mass ppm.

5. A method for manufacturing the electrolytic manganese dioxide according to any one of claims 1 to 4, characterized in that, The manufacturing method of the electrolytic manganese dioxide is an electrolysis method in which the current density during electrolysis is set to J, and the ratio of the square of the manganese ion concentration [Mn 2+ and the hydrogen ion concentration [H + in the electrolyte is set to X, and [Mn 2+ at the end of electrolysis is less than [Mn 2+ at the start of electrolysis, and there exists a period that satisfies both of the following formulas (1) and (2) and exceeds 6 days When X = [Mn 2+ / [H + 2 then​ J ≤ X + 0.22 1) X / J 2 ≤2.10 2), Among them, the unit of the current density J is A / dm 2 , the units of the manganese ion concentration [Mn 2+ and the hydrogen ion concentration [H + are mol / L.

6. The method for manufacturing the electrolytic manganese dioxide according to claim 5, wherein, the electrolytic solution is a mixed solution of manganese sulfate and sulfuric acid.

7. The method for manufacturing the electrolytic manganese dioxide according to claim 5 or 6, wherein, the manganese ion concentration at the start of electrolysis is above 25 g / L.

8. A positive electrode active material for a battery, characterized in that, it contains the electrolytic manganese dioxide according to any one of claims 1 to 4.

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