JP7661695B2 - Cathode for electrolytic manganese dioxide production - Google Patents

Description

The present invention relates to a cathode for producing electrolytic manganese dioxide, and more specifically, to a cathode used in producing electrolytic manganese dioxide to be used as a positive electrode active material in, for example, manganese dry batteries, particularly alkaline manganese dry batteries.

Electrolytic manganese dioxide is known, for example, as a positive electrode active material for manganese dry batteries, especially alkaline manganese dry batteries, and has the advantages of being excellent in storage stability and inexpensive. In particular, alkaline manganese dry batteries that use electrolytic manganese dioxide as the positive electrode active material have excellent discharge characteristics over a wide range of discharge rates, from low-rate discharge to high-rate discharge, and are therefore widely used in electronic devices, portable players, portable information devices, and even game consoles and toys, with demand for them growing not only in Japan but also around the world.

Electrolytic manganese dioxide is generally produced by electrolytic oxidation and deposition on the anode by passing an electric current between the anode and cathode in a manganese sulfate electrolyte, which is acidic with sulfuric acid. Generally, titanium is used for the anode, and graphite is mainly used for the counter electrode, the cathode, although copper and steel are used in rare cases (Patent Document 1).

When producing electrolytic manganese dioxide, the temperature of the electrolyte must be kept at a high temperature of 93°C to 98°C, and since the electrolysis period is long, lasting from 1 to 4 weeks, a layer of oil with a high boiling point, such as paraffin, is floated on top of the electrolyte to prevent the electrolyte from evaporating.

This paraffin adheres to and is absorbed into the electrolytic manganese dioxide deposit not only during electrolysis, but also when the anode on which electrolytic manganese dioxide is deposited is removed from the electrolytic cell and passes through the paraffin oil layer after electrolysis is completed, affecting the product quality of electrolytic manganese dioxide. Therefore, electrolysis methods that remove paraffin absorbed into electrolytic manganese dioxide by washing with hot water or that incorporate measures to minimize the incorporation of paraffin are being investigated (Patent Document 2).

However, unlike the anode side where the electrolytic manganese dioxide precipitation reaction takes place, the cathode side where the hydrogen generation reaction takes place does not directly affect product quality, so it has not received much attention and there have been few cases in which it has been studied in the past.

However, our research has revealed that when graphite is used for the cathode, the cathode deteriorates, resulting in a significant decrease in the production efficiency of electrolytic manganese dioxide.

WO2000/037714 publication JP 2001-247987 A

The object of the present invention is to provide a cathode modified for the production of electrolytic manganese dioxide, which is coated with a copper film conforming to the cathode surface shape, and a method for producing the same.

The inventors investigated the performance expression and deterioration behavior of cathodes used in electrolytic manganese dioxide production, and conducted extensive research into modifying the cathode. As a result, they discovered that by using a cathode coated with a copper film conforming to the cathode surface shape, not only is the deterioration of the cathode suppressed, but the performance can be stably maintained over a long period of time and the cathode has excellent durability, which led to the completion of the present invention. In other words, the present invention is a cathode for electrolytic manganese dioxide production composed of a graphite plate coated with a copper film.

The present invention is described in detail below.

The cathode for producing electrolytic manganese dioxide of the present invention is composed of a graphite plate coated with a copper film.

Graphite plates are mostly in the form of plates used in metal refining and plating, but are not essentially limited to this shape. Also, as mentioned above, if paraffin is contained inside the graphite plate, it is desirable to remove most of the paraffin by washing with hot water, treating with an organic solvent, degreasing treatment using an alkaline solution, or by burning, and it is desirable that there is no paraffin at least near the surface that will later be coated with the copper coating. In industry, degreasing cleaners composed mainly of alkaline components are sometimes used.

The copper coating is a copper-based metal, and there is no restriction on its purity, but it is preferable that it contains 60 wt% or more copper, and it may be a composite coating with transition metals such as iron or nickel, or non-metals such as sulfur or phosphorus.

The copper coating acts as an electrode catalyst by being on the graphite plate and maintaining electrical contact. The hydrogen generation electrode catalytic activity of copper is known to be superior to that of carbon, the material from which graphite is made, even in terms of basic chemistry (U.R. Evans, THE CORROSION AND OXIDATION OF METALS). For example, the hydrogen overvoltage of carbon is 0.7 V, while that of copper is 0.53 V, and it is said to show excellent activity at low hydrogen overvoltages.

The thickness of the copper coating applied to the graphite plate surface is not limited, but is preferably 0.3 μm to 100 μm, more preferably 0.5 μm to 100 μm, even more preferably 0.5 μm to 50 μm, and most preferably 1 μm to 20 μm. The graphite plate surface may have irregularities of several μm to several mm, and it is desirable for these irregularities on the graphite plate surface to be completely covered with a copper coating of the above-mentioned thickness, but it is not necessary to cover them completely. The coverage may be at least such that copper can exhibit electrocatalytic activity, for example, a coverage of 40%. Note that the parts of the graphite plate that are not immersed in the electrolyte, such as the power supply part that supplies current to the graphite plate, do not contribute to the electrocatalytic reaction, and therefore do not necessarily need to be covered with a copper coating.

The cathode for producing electrolytic manganese dioxide of the present invention can be produced by using a graphite plate as the working electrode and coating it with a copper film by electroplating or electroless plating in an electrolyte containing copper ions.

Methods for coating a graphite plate with a copper film include, for example, electroplating and electroless plating.

In electroplating, a graphite plate is immersed in an electrolyte containing copper ions, and a current is passed between the graphite plate and a counter electrode (anode) for a specified period of time to coat the plate with copper.

An electrolyte containing copper ions is prepared by dissolving copper salts such as copper sulfate, copper hydrochloride, copper nitrate, and copper pyrophosphate in the electrolyte. In addition to the copper salt, the electrolyte may contain additives such as complexing agents such as citrate ions, tartrate ions, phosphate ions, and pyrophosphate ions, or gloss agents such as dextrin and lauryl sulfate ions, or sulfur-containing substances such as thiourea. In addition, the electrolyte containing copper ions may be mixed with other metal ions such as transition metal ions such as iron ions and nickel ions to obtain a copper-based alloy coating. However, there is no problem if the electrolyte contains metal ions such as manganese ions that do not directly interact with copper ions and do not precipitate on the graphite plate.

The pH of the electrolyte may be adjusted depending on the additives and properties of the metal ions contained in the electrolyte, but in the case of the present invention, it is generally pH 0.1 or more and pH 7 or less.

The copper ion concentration of the electrolyte is not particularly limited, but for example, 10 mg/L or more and 30 g/L or less is applied. The electrolyte temperature is also not limited, but for example, 40°C or more and 98°C or less is applied.

For the counter electrode (anode), insoluble precious metals such as platinum and iridium are primarily used, but by controlling the concentration of components in the electrolyte, even metals that undergo electrolytic dissolution, such as copper, can be used.

The current applied during electrolysis is selected in the range of 20 A/m ² to 1000 A/m ² as the current density of the graphite plate, and electrolysis is continued until a predetermined copper coating thickness is achieved.

In the electroless plating method, a reducing agent is added to an electrolyte containing copper ions, and a pretreated graphite plate is immersed in the electrolyte for a specified period of time to be coated with copper.

An electrolyte containing copper ions is prepared by dissolving copper salts such as copper sulfate, copper hydrochloride, copper nitrate, and copper pyrophosphate in the electrolyte. In addition to the copper salt, the electrolyte may contain additives such as complexing agents such as citrate ions, tartrate ions, phosphate ions, and pyrophosphate ions, polyacetylene glycol surfactants, sulfur-containing substances such as thiourea, and boric acid. In addition, transition metal ions such as nickel ions may be mixed into the electrolyte containing copper ions to obtain a copper-based alloy coating.

Sodium hypophosphite is typically used as a reducing agent.

The pH of the electrolyte is adjusted according to the additives and the properties of the metal ions contained in the electrolyte, but in the case of the present invention, it is adjusted to be generally pH 7 or higher and pH 12 or lower.

The copper ion concentration of the electrolyte is not particularly limited, but for example, 0.5 g/L or more and 30 g/L or less is applied. The electrolyte temperature is also not limited, but for example, 20°C or more and 80°C or less is applied.

The bath load in electroless plating (the V/A ratio of the area A ( ^m2 ) of the object to be plated to the volume V ( ^m3 ) of the electrolyte) is selected in the range of approximately 5 to 30, and immersion is continued until a predetermined copper coating thickness is achieved.

Pretreatment of graphite plates may involve washing with hot water, treatment with organic solvents, degreasing with alkaline liquid, or plating with another metal as a base for the copper coating in order to remove paraffin from the graphite plate. In industry, degreasing cleaners mainly composed of alkaline components may be used to remove paraffin from the graphite plate.

The cathode for producing electrolytic manganese dioxide of the present invention suppresses cathode deterioration and can maintain a low electrolysis voltage, thereby achieving efficient and stable production efficiency of electrolytic manganese dioxide.

1 is a photograph showing the appearance of a cathode obtained in Comparative Example 3. 1 is a photograph showing the appearance of the cathode obtained in Example 1. 2 is a cross-sectional photograph of the surface vicinity of the cathode obtained in Example 1. 1 is a photograph showing the appearance of the cathode obtained in Example 3. 1 is a photograph showing the appearance of a cathode obtained in Example 4. 1 is a photograph showing the appearance of the cathode obtained in Example 7. 1 is a photograph showing the appearance of a cathode obtained in Example 8. 1 is a photograph showing the appearance of a cathode obtained in Example 9. 1 is a Tafel plot showing the change in logarithm of current density and potential during hydrogen generation in Examples 1 to 4, Examples 8 and 9, and Comparative Example 4. 1 is a Tafel plot showing the change in logarithm of current density and potential during hydrogen generation in Comparative Examples 1 and 3 to 6.

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

<Method of preparing cathode for measuring potential performance>
A cathode substrate plate such as graphite was cut to have a surface of 1 cm square so that the measurement direction was the only exposed surface. A nickel lead wire was embedded on the back side and, while maintaining electrical contact, the plate was embedded in a cured resin (Technovit #4071, manufactured by Marutoh). The exposed surface was then polished with #1500 sandpaper to produce a cathode (electrode area 1 x 1 ^cm2 ).

To prepare a cathode coated with a copper film, the exposed surface of the cathode was immersed in an electrolyte containing copper ions and coated with a copper film using electroplating or electroless plating.

<Measurement of potential performance>
The exposed surface of the cathode or the copper-coated cathode was immersed in a 28 g/L sulfuric acid solution at 96°C, a platinum plate was used as the counter electrode, and a saturated calomel electrode (S.C.E) was used as the reference electrode. The electrodes were connected to a potentiogalvanostat (HA-151B, Hokuto Denko Corporation), and a current of 0.05 to 1 A/ ^dm2 was applied to read the value of the cathode potential relative to the S.C.E reference electrode.

The cathode potential when a current of 0.5 A/ ^dm2 was applied was shown as a representative value of the cathode potential of each cathode. In addition, as another performance index of each cathode, the degree of potential change between 0.05 and 1 A/ ^dm2 was shown as the Tafel slope (used as an index of the electrochemical hydrogen generation mechanism of the electrode catalyst material).

<Electrolytic test method>
An electrolysis test was performed in which a sulfuric acid-manganese sulfate mixed solution was used as the electrolyte, and a current was applied between the cathode or the copper-coated cathode and the titanium anode while continuously supplying a manganese sulfate replenishment solution with a manganese ion concentration of 46 g/L into the electrolytic cell, to deposit electrolytic manganese dioxide on the titanium anode. At this time, electrolysis was performed for 18 days while adjusting the electrolysis current density to 0.68 A/dm ² , the electrolysis temperature to 96° C., and the sulfuric acid concentration in the electrolytic cell to 34 g/L. During the electrolysis, a mercury/mercury sulfate electrode was used as a reference electrode, and the cathode potential was measured.

Comparative Example 1
A graphite plate (PSG322, manufactured by SEC) infiltrated with 24 mg/g of paraffin was used to prepare a cathode, and potential measurements were performed. The cathode potential was −1.02 V vs. S.C.E., and the Tafel slope was −0.080 V/dec.

Comparative Example 2
When the graphite plate of Comparative Example 1 was subjected to paraffin extraction and removal treatment with hexane, the amount of remaining paraffin was less than 0.5 mg/g. A cathode was made from the graphite plate subjected to the paraffin removal treatment, and the potential was measured. The cathode potential was −0.70 V vs. S.C.E.

Comparative Example 3
When the graphite plate of Comparative Example 1 was subjected to a paraffin removal treatment by combustion, the amount of remaining paraffin was <0.5 mg/g. A cathode was prepared using this graphite plate subjected to the paraffin removal treatment, and the potential was measured. The cathode potential was -0.62 V vs. S.C.E, and the Tafel gradient was -0.083 V/dec. A photograph of the appearance of the obtained cathode is shown in Figure 1.

Example 1
A cathode made of a graphite plate that had been subjected to the paraffin removal treatment of Comparative Example 3 was immersed in an electrolyte containing 10 g/L of copper (Cu ²⁺ ) ions and 35 g/L of sulfuric acid, and a platinum plate was used as the counter electrode. While maintaining the temperature at 70° C., electroplating was performed for 50 minutes at a current density of 0.05 A/dm ² to obtain a cathode. The cathode potential after electroplating was −0.39 V vs. S.C.E, and the Tafel gradient was −0.060 V/dec. A photograph of the appearance of the obtained cathode is shown in FIG. 2, and a photograph of a cross section near the surface is shown in FIG. 3.

Examples 2 to 4
A cathode was obtained by electroplating in the same manner as in Example 1, except that the electroplating conditions of the current density and time were changed in Example 1. These electroplating conditions and the cathode potential and Tafel slope values of the cathode after electroplating are shown in Table 1.

Figure 4 shows a photograph of the appearance of the cathode obtained in Example 3, and Figure 5 shows a photograph of the appearance of the cathode obtained in Example 4.

Example 5
A cathode made of a graphite plate subjected to the paraffin removal treatment of Comparative Example 3 was immersed in an electrolytic solution prepared by adding copper (Cu ²⁺ ) ions to an aqueous solution having a manganese ion concentration of 27 g/L and a sulfuric acid concentration of 36 g/L to obtain a cathode by electroplating for 60 minutes while maintaining a current density of 0.57 A/dm ² and a temperature of 96° C., and a hydrogen gas bubble generation was confirmed from the exposed surface of the cathode during electroplating, but after electroplating, the exposed surface of the cathode turned copper color, and it was visually confirmed that the cathode was coated with a copper film. The cathode potential of the cathode after electroplating was −0.47 V vs. S.C.E.

Examples 6 to 7
In Example 5, electroplating was performed in the same manner as in Example 5, except that the concentrations of copper (Cu ²⁺ ) ions added to the aqueous solution were 100 mg/L and 1000 mg/L, to obtain cathodes. In both cases, hydrogen gas bubbles were observed to be generated from the exposed surface of the cathode during electroplating, but after electroplating, the exposed surface of the cathode turned copper color, and it was visually confirmed that it was covered with a copper coating. These electroplating conditions and the cathode potential value of the cathode after electroplating are shown in Table 1. A photograph of the appearance of the cathode obtained in Example 7 is shown in FIG. 6.

Example 8
A cathode made of a graphite plate subjected to the paraffin removal treatment of Comparative Example 3 was immersed in an electrolytic solution containing 2 g/L of copper (Cu ²⁺ ) ions, 0.14 g/L of nickel (Ni ²⁺ ) ions, 13.5 g/L of sodium citrate, 29 g/L of sodium hypophosphite monohydrate, 31 g/L of boric acid, and 0.4 g/L of starch under the condition of a bath load (V/A) of 10, and electroless plating was performed for 30 minutes while keeping the pH at 9.0 and the temperature at 60° C. to obtain a cathode. After electroless plating, the entire immersed part of the cathode turned copper color, and it was visually confirmed that the cathode was coated with a copper coating. The cathode potential of the cathode measured after removing the other copper coating parts with sandpaper, leaving only the exposed surface of the cathode, was −0.46 V vs. S.C.E, and the Tafel gradient was −0.052 V/dec. A photograph of the appearance of the obtained cathode is shown in FIG.

Example 9
A cathode was obtained by electroless plating in the same manner as in Example 8, except that the pH of the electrolytic solution was 10.5. As in Example 8, after electroless plating, the entire immersed part of the cathode turned copper color, and it was visually observed that the cathode was coated with a copper film. The cathode potential of the cathode measured after removing the copper film with sandpaper, leaving only the exposed surface of the cathode, was −0.47 V vs. S.C.E, and the Tafel slope was −0.059 V/dec. A photograph of the appearance of the obtained cathode is shown in FIG.

Comparative Example 4
A cathode was prepared using a copper plate instead of the graphite plate of Comparative Example 1, and potential measurement was performed. The cathode potential was −0.49 V vs. S.C.E, and the Tafel slope was −0.062 V/dec.

Comparative Example 5
A cathode was prepared by using a nickel plate instead of the graphite plate of Comparative Example 1, and potential measurement was performed. The cathode potential was −0.59 V vs. S.C.E, and the Tafel slope was −0.077 V/dec.

Comparative Example 6
A cathode was prepared using a platinum plate instead of the graphite plate of Comparative Example 1, and potential measurements were performed. The cathode potential was −0.35 V vs. S.C.E, and the Tafel slope was −0.034 V/dec.

Figure 9 shows Tafel plots showing the change in logarithm of current density and potential during hydrogen generation for Examples 1 to 4, Examples 8 and 9, and Comparative Example 4, and Figure 10 shows Tafel plots showing the change in logarithm of current density and potential during hydrogen generation for Comparative Examples 1 and 3 to 6.

As described above, the cathode potential was improved by coating a thin copper film on a graphite plate from which the paraffin had been removed. The characteristic level was superior to that of copper metal and close to that of platinum precious metal.

Example 10
A cathode was obtained in the same manner as in Example 8, except that electroless plating was performed for 60 minutes. An electrolytic test was performed on the obtained cathode according to the <Electrolytic Test Method>. The paraffin content of the obtained cathode was <0.5 mg/g, the copper content was 1.88 mg/ ^cm2 , and the copper coating thickness was 2.10 μm. The cathode potential relative to the sulfuric acid/mercury sulfate reference electrode was −0.91 V vs. _Hg2SO4 . These values are shown in Table ₂ .

Examples 11 to 14
Cathode was obtained in the same manner as in Example 10, except that the electroless plating time, copper content, and copper coating thickness were changed. Electrolysis test was performed on the obtained cathode according to <Electrolysis test method>. The values are summarized in Table 2. In Examples 13 and 14, paraffin was detected in the cathode, and it was presumed that paraffin re-permeated into the graphite substrate during electrolysis.

Comparative Example 7
An electrolysis test was carried out according to the <Electrolysis Test Method> using the graphite plate that had been subjected to the paraffin removal treatment of Comparative Example 3 as the cathode. The paraffin content of this cathode was <0.5 mg/g. The cathode potential of this cathode relative to the sulfuric acid/mercury sulfate reference electrode was -1.35 _V vs. _Hg2SO4 .

Comparative Example 8
An electrolysis test was carried out according to the <Electrolysis Test Method> using a graphite plate (PSG322, manufactured by SEC) permeated with 54 mg/g of paraffin as the cathode. The cathode potential of this cathode with respect to the sulfuric acid/mercury sulfate reference electrode was −1.52 V vs. Hg ₂ SO ₄ .

Comparative Example 9
An electrolysis test was carried out using a copper plate as a cathode according to the <Electrolysis Test Method>. The cathode potential of this cathode with respect to a sulfuric acid/mercury sulfate reference electrode was −1.08 V vs. Hg ₂ SO ₄ .

As described above, by coating a thin copper film by electroless copper plating on a graphite plate from which paraffin had been removed by the combustion method, the cathode potential was improved even in electrolysis for electrolytic manganese dioxide deposition using a sulfuric acid-manganese sulfate electrolyte. The characteristic level was superior to that of copper metal, and good performance was demonstrated even when paraffin re-permeated into the graphite substrate during electrolysis.

Example 15
A cathode was obtained in the same manner as in Example 8, except that a graphite plate (PSG322, manufactured by SEC) infiltrated with 54 mg/g of paraffin was immersed in a degreasing cleaner (SC-60, manufactured by Asahi Yushi Chemicals) at 55°C for 15 minutes, washed with water, and then electroless plating was performed for 60 minutes. An electrolytic test was performed on the obtained cathode according to the <Electrolytic test method>. The paraffin content of the obtained cathode was <0.5 mg/g, and the copper coating thickness was 1.8 μm. The cathode potential relative to a sulfuric acid/mercury sulfate reference electrode of this cathode was −0.97 V vs. Hg ₂ SO _4. These values are shown in Table 3.

Example 16
A graphite plate (PSG322, manufactured by SEC) infiltrated with 54 mg/g of paraffin was used, and paraffin was removed by combustion, followed by electroplating in the same manner as in Example 1 to obtain a cathode. An electrolytic test was performed on the obtained cathode according to the <Electrolytic Test Method>. The paraffin content of the obtained cathode was <0.5 mg/g, and the copper coating thickness was 2.4 μm. The cathode potential of this cathode relative to a sulfuric acid/mercury sulfate reference electrode was −1.06 V vs. Hg ₂ SO _4. These values are shown in Table 3.

Example 17
A graphite plate (PSG322, manufactured by SEC) permeated with 54 mg/g of paraffin was immersed in a degreasing cleaner (SC-60, manufactured by Asahi Yushi Chemicals) at 55°C for 15 minutes, washed with water, and then electroplated in the same manner as in Example 16 to obtain a cathode. An electrolytic test was performed on the obtained cathode according to the <Electrolytic Test Method>. The paraffin content of the obtained cathode was <0.5 mg/g, and the copper coating thickness was 2.6 μm. The cathode potential of this cathode relative to a sulfuric acid/mercury sulfate reference electrode was −1.03 V vs. Hg ₂ SO _4. These values are shown in Table 3.

Example 18
A graphite plate (PSG322, manufactured by SEC) permeated with 54 mg/g of paraffin was subjected to electrolytic degreasing treatment for 15 minutes with a degreasing cleaner (SC-60, manufactured by Asahi Yushi Chemicals) at 40°C, washed with water, and then electroplated in the same manner as in Example 16 to obtain a cathode. An electrolytic test was performed on the obtained cathode according to the <Electrolytic Test Method>. The paraffin content of the obtained cathode was <0.5 mg/g, and the copper coating thickness was 3.0 μm. The cathode potential of this cathode relative to a sulfuric acid/mercury sulfate reference electrode was −1.07 V vs. Hg ₂ SO _4. These values are shown in Table 3.

As described above, by coating a thin copper film by either electroless plating or electroplating on a graphite plate from which some of the paraffin had been removed using a commercially available degreasing cleaner, the cathode potential was improved in electrolysis for electrolytic manganese dioxide deposition using a sulfuric acid-manganese sulfate electrolyte. The characteristic level was excellent, equivalent to or better than that of copper metal.

The present invention has excellent activity in the hydrogen generation electrode catalytic reaction at the cathode and can maintain a low electrolysis voltage for a long period of time, making it possible to stably produce electrolytic manganese dioxide with a low power consumption rate.

1 Graphite exposed surface 2 Embedding resin part 3 Graphite exposed surface covered with copper film 4 Embedding resin 5 Copper film 6 Graphite

Claims (11)

A cathode for electrolytic manganese dioxide production, characterized by being composed of a graphite plate coated with a copper film. The cathode for producing electrolytic manganese dioxide as described in claim 1, characterized in that the thickness of the copper coating is 0.3 μm or more and 100 μm or less. The cathode for producing electrolytic manganese dioxide according to claim 1 or 2, characterized in that the copper coating is made of a copper-based metal containing 60 wt% or more of copper. 4. The cathode for producing electrolytic manganese dioxide according to claim 1, wherein the copper coating is made of a copper-based metal containing iron or nickel. A cathode for producing electrolytic manganese dioxide according to any one of claims 1 to 4, characterized in that the copper coating is composed of a copper-based metal containing phosphorus or sulfur. A cathode for producing electrolytic manganese dioxide as described in any one of claims 1 to 5, characterized in that the graphite plate contains paraffin. A method for producing a cathode for producing electrolytic manganese dioxide according to any one of claims 1 to 6, characterized in that a graphite plate is used as the working electrode and a copper coating is formed by electroplating in an electrolyte containing copper ions. A method for producing a cathode for producing electrolytic manganese dioxide according to any one of claims 1 to 6, characterized in that a graphite plate is used as the working electrode and a copper coating is formed by electroless plating in an electrolyte containing copper ions. 9. The method for producing a cathode for producing electrolytic manganese dioxide according to claim 7 or 8, wherein the copper ion concentration in the copper ion-containing electrolyte is 0.01 g/L or more and 30 g/L or less. A method for producing electrolytic manganese dioxide, characterized by using a cathode for producing electrolytic manganese dioxide according to any one of claims 1 to 6. A method for producing a positive electrode material for a battery, the positive electrode material being synthesized using electrolytic manganese dioxide produced by the method for producing electrolytic manganese dioxide according to claim 10 .