JPH0555983B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for manufacturing a dry cell using manganese dioxide, and particularly to improving the charging characteristics of a dry cell using manganese dioxide, which is suitable for dry cells.

[Conventional technology]

Manganese dioxide powder is used as the positive electrode material of so-called manganese dry batteries.

There are four types of manganese dioxide used: electrolytic manganese dioxide, chemically synthesized manganese dioxide, natural manganese dioxide, and activated chemically treated manganese dioxide. Among these, electrolytic manganese dioxide is produced by, for example, leaching rhodochrosite with sulfuric acid to make a manganese sulfate aqueous solution, removing impurities such as iron by precipitation, and then converting it to hard lead or metallic titanium at a temperature of about 80°C or higher. It is produced by depositing it on the anode by direct current electrolysis. In addition, natural manganese dioxide is used for dry batteries by pulverizing natural ores as they are.

On the other hand, activated chemically treated manganese dioxide is completely different from the above method, in which various manganese oxide ores are roasted and thermally decomposed in an autogenous atmosphere to produce manganese sesquioxide and trimanganese tetraoxide.
It is activated manganese dioxide obtained by treating this with mineral acids such as sulfuric acid, hydrochloric acid, and nitric acid. For example, publications disclosing the manufacturing method include JP-A-53-88696 and JP-A-60-221324.

[Problem that the invention seeks to solve]

The electrolytic manganese dioxide mentioned above is certainly of high quality and highly active, and when incorporated into a dry battery, the battery exhibits excellent heavy load discharge and light load discharge characteristics, but the current density during electrolytic manufacture is 0.8
Since it is small at ~2.0 A/cm ² , its productivity is low, and the amount of power used is enormous, resulting in a high overall cost. Furthermore, natural manganese dioxide has been widely used, and this is probably because manganese dioxide ore is relatively inexpensive and can be obtained from nature in large quantities. However, natural manganese dioxide has a problem in that it has particularly poor heavy load discharge characteristics.

On the other hand, the conventionally known activated chemically treated manganese dioxide (ACM), when filled into a dry battery, has a heavy load discharge characteristic close to that of electrolytic manganese dioxide, and has been recently used due to its low cost. It is attracting attention. Generally, the tap density is
The filling state is as small as 1.1 to 1.4 g/cm ³ and extremely porous. Therefore, the loading amount of the active substance manganese dioxide in the battery is small;
Light load discharge of the battery is significantly reduced.

In order to solve this problem, an attempt has been made to roll-press activated chemically treated manganese dioxide into a flat plate-shaped compression molded product, and then crush it to the desired particle size to make it heavier (Unexamined Japanese Patent Publication No. Showa 60-221324
Publication No.).

But activated chemical treatment manganese dioxide (ACM)
When used in dry batteries that mainly contain zinc chloride, ACM, which has better heavy load discharge characteristics, has the problem that the internal resistance of the battery increases during light load discharge, and as a result, the pulse discharge characteristics deteriorate significantly. It was hot.

In order to prevent this increase in internal resistance, the amount of electrolyte solution or the amount of acetylene black, which is a conductive material, has been increased. However, there are problems that cannot be solved, such as increasing the amount of electrolyte will increase battery leakage, and increasing the amount of conductive material will decrease the amount of manganese dioxide, reducing light load discharge capacity. Nakatsuta.

In particular, ACM has tap density (T.
D.) is 1.1 to 1.4 g/cm ³ , electrolytic manganese dioxide (TD 2.2 to 2.4 g/cm ³ ), natural manganese dioxide (T.
D. 2.1 to 2.3 g/cm ³ ), it was an important issue to improve the properties using techniques other than compounding.

Further, attempts have been made to use a simple mixture of ACM and natural manganese dioxide as a positive electrode active material, but no significant improvement in pulse discharge characteristics has been obtained.

The present invention solves these conventional problems and particularly aims to improve the discharge characteristics of a battery in an economical manner.

[Means for solving problems]

In order to achieve the above object, the present inventors conducted extensive research and found that a specific ACM and natural manganese dioxide were mixed, compression molded using a roll press, and then the molded manganese dioxide mixture was pulverized. The inventors have discovered that the above-mentioned characteristics are significantly improved when used in dry batteries, and have now produced the dry batteries of the present invention.

That is, the present invention uses ACM obtained by roasting manganese ore or manganese salt at a temperature of 400°C to 1100°C and then acid-treating it as a raw material, and mixes this ACM powder with natural manganese dioxide powder, 10 tons/
It is compression molded into a flat plate using a roll press under a pressure of cm ² , and then pulverized to a predetermined particle size and provided to a dry battery as a positive electrode active material.

The manganese ore used here is
MnO ₂ (soft manganese ore), MnCO ₃ (rhodochosite),
Those containing Mn ₂ O ₃ , Mn ₃ O ₄ or the like as a main component are preferred.

In addition, as manganese salts, MnSO ₄ , MnCO ₃ ,
Examples include MnCl ₂ and Mn(NO ₃ ) ₂ .

Generally, when manganese ore and manganese salt (MnSO ₄ ) are roasted in an autogenous atmosphere, the
It is converted to Mn ₂ O ₃ from around 800°C to 1000°C, and further converted to Mn ₃ O ₄ from around 800 to 1000°C. The roasting time is not particularly limited, but is usually 0.5 to 5 minutes.
Any time is fine.

Also, MnSO ₄ decomposes at 850℃ to become Mn ₃ O ₄ ,
Further heating at 530 to 940℃ causes an oxidation reaction.
_{Produces Mn2O3} .

Examples of this reaction formula are shown in formulas (1), (2), and (2)′.

2MnO ₂ →Mn ₂ O ₃ +1/2O ₂ ...(1) 3MnSO ₄ →Mn ₃ O ₄ +2SO ₃ +SO ₂ ...(2) 2/3Mn ₃ O ₄ +1/6O ₂ →Mn ₂ O ₃ ...( 2)′ Mn ₂ O ₃ or Mn 2 O 3 obtained by such roasting
The Mn ₃ O ₄ is then treated with mineral acid. Examples of the mineral acids used include sulfuric acid, nitric acid, and hydrochloric acid.

This treatment produces manganese dioxide. The reaction formula is as follows.

Mn ₂ O ₃ +H ₂ SO ₄ →MnO ₂ +MnSO ₄ +H ₂ O Mn ₃ O ₄ +2H ₂ SO ₄ →MnO ₂ +2MnSO ₄ +2H ₂ O The obtained manganese dioxide cake is thoroughly washed, for example, in running water, and ammonia It can be produced by neutralizing with water, an aqueous caustic soda solution, or an aqueous sodium carbonate solution, followed by drying at a temperature of 60 to 110°C to remove water. These manganese dioxides have a crystal structure mainly composed of the γ type.

In addition, the natural manganese dioxide powder used in the present invention is manganese dioxide for use in dry batteries with a purity of 75% or more, and 80% purity of Gabon ore, Australian ore, etc.
~86% is preferred.

As a specific pressing method, activated chemically treated manganese dioxide (ACM) powder obtained by acid-treating Mn ₂ O ₃ or Mn ₃ O ₄ obtained by roasting manganese ore or manganese salt, and natural manganese dioxide powder are used. Both are crushed to 100mesh (150μm in diameter) or less.

It is advantageous to mix ACM in a range of 40 to 70% and natural manganese dioxide in a range of 60 to 30%, press and crush the mixture in order to obtain a dry battery with excellent discharge characteristics. When pressed in this range, the compacted density increases by mixing rather than pressing alone, and the electrochemical activity of both manganese dioxides is brought out, resulting in better properties than the arithmetic average value of the battery characteristics of both manganese dioxides. It comes to show that.

The pressure of the roll press during compression molding is generally 1 to 10 tons/cm ² , but even a low pressure in the range of 1 to 4 tons/cm ² can sufficiently achieve the purpose.

In addition, the press pressure and number of presses vary depending on the blending ratio of raw manganese dioxide, particle size and its distribution, and shape, but the tap density is 2.0 g/cm ²
In this case, it is sufficient to press 2 to 4 times at a pressure of 2 tons/cm ² , and there is no noticeable difference in the effect even if the press is pressed 5 or more times.

[Effect]

By compressing and pulverizing both manganese dioxide powders, they have the following excellent characteristics that cannot be obtained by mixing alone.

First of all, pulse discharge during light load discharge is significantly improved.

Secondly, when used as a mixture, the packing density is improved and the light load discharge characteristics are significantly improved.

〔Example〕

Example A Manganese oxide ore (soft manganese ore) with a purity of 84% was crushed into a powder of 60 mesh or less. This powder was roasted in an autogenous atmosphere at about 850°C. The main component was α-Mn ₂ O ₃ . Powder after roasting
The powder was pulverized to 100 mesh or less, poured into a 3N sulfuric acid solution at 90°C, and reacted for 2 hours. Next, the reaction product was thoroughly washed with water, filtered, neutralized with aqueous ammonia, further washed with water, and finally dried with ACM.
A powder was obtained. This ACM powder has a purity of 82.1%,
As a result of X-ray diffraction, the crystal structure was manganese dioxide mainly in the γ type.

Natural manganese dioxide was obtained by pulverizing manganese dioxide for dry electricity production from Gabon to 100 mesh or less using a pulverizer. The purity is 83.8%, and the crystal structure is mainly γ-type manganese dioxide.

Next, 80 parts by weight of ACM powder and 30 parts by weight of natural manganese dioxide were mixed, molded using a roll press at a pressure of 3 tons/cm ² , and the molded body was crushed to form a powder of 100 mesh or less. did.

A battery was manufactured using these powders as a positive electrode active material by the method shown below.

4.00 g of mixed manganese dioxide of the present invention and 0.67 g of acetylene black were thoroughly mixed, and 3.33 g of an aqueous solution containing 25% by weight zinc chloride and 2.5% by weight ammonium chloride was added to form a uniform positive electrode mixture. Inventive product A, which is an R6 type dry battery, was manufactured.

Examples B and C Using the same ACM and natural manganese dioxide as in Example A, 50 parts by weight of ACM powder and 50 parts by weight of natural manganese dioxide were mixed, roll pressed and pulverized under the same conditions. A dry battery of the same type as Invention B was manufactured. In addition, a dry battery of the same type was manufactured by mixing 40 parts by weight of ACM powder and 60 parts by weight of natural manganese dioxide, roll pressing, and pulverizing the mixture, and designated it as product C of the present invention.

Comparative Examples D, E, F The ACM produced in Example A was compression molded using a roll press machine at a pressure of 3 tons/cm ² , and then the molded body was crushed to form a powder of 100 mesh or less. By mixing 70, 50, and 40 parts by weight of this powder with 30, 50, and 60 parts by weight of natural manganese dioxide similar to Example A, an R6 dry battery having the same composition as Example A was produced without press crushing. The comparative products were designated as D, E, and F, respectively.

A discharge test was conducted on each of these R6 type dry batteries, and the results are shown in Figure 1.

Figure 1 shows the changes in battery internal resistance when the invention products A, B, and C and the comparative products D, E, and F were continuously discharged with a load resistance of 1.2KΩ.
B, C, D, E, and F, and the changes in terminal voltage when a pulse discharge of 10 Ω for 3 seconds is superimposed once a day during a continuous discharge of 1.2 KΩ are A', B', C', D' ，
Denoted as E′ and F′.

〔Effect of the invention〕

As described above, the dry battery of the present invention using mixed manganese dioxide as a positive electrode active material has improved pulse discharge characteristics during light and medium load discharges, and further improved light load discharge.

[Brief explanation of the drawing]

Figure 1 shows examples of products A, A', B, B',
It is a comparison diagram regarding the discharge curve and internal resistance value of C and C' and comparative products D, D', E, E', F, and F'. A, B, C, D, E, F... Internal resistance curve during continuous discharge, A', B', C', D', E', F'... Internal resistance curve when pulse discharge is superimposed during continuous discharge. discharge curve.

Claims (1)

[Claims] 1 Manganese oxide (Mn ₂ O ₃ or Mn ₃ O ₄ ) obtained by roasting manganese ore or manganese salt
is acid-treated to produce an activated chemically treated manganese dioxide powder, this powder is mixed with natural manganese dioxide powder, and compression molded using a roll press under a pressure of 1 to 10 tons/cm ² , and then mixed manganese dioxide is obtained. A method for producing a dry battery, characterized by pulverizing a molded body and using it as a positive electrode active material.