JPH059773A - Preparation of high performance gamma-type manganese dioxide and battery using said manganese dioxide - Google Patents

Abstract

PURPOSE: To obtain a high-performance γ type manganese dioxide which allows easy pulverization, has high electrical conductivity and has an excellent discharge characteristic when used as a positive pole material of a battery.

CONSTITUTION: The short fibers of carbon fibers or graphite fibers provided with the films of manganese oxide on the surfaces are dispersed into a manganese electrolyte and the eutectoid of the short fibers with the manganese dioxide is effected by an electrolysis, by which the battery consisting of the highperformance γ type manganese dioxide contg. ≥90 wt.% M_nO₂ as its positive pole material is produced.

COPYRIGHT: (C)1993,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing high-performance γ-type manganese dioxide suitable as a positive electrode material for batteries such as manganese dry batteries, alkaline manganese batteries and manganese dioxide lithium batteries, and batteries using this manganese dioxide. .

[0002]

2. Description of the Related Art Since manganese dioxide has the greatest effect on the performance of dry batteries, high purity γ-type manganese dioxide produced by electrolysis has been frequently used instead of naturally occurring low purity products.

In the conventional electrolysis method, the current density is 5 to 7 mA / cm ²
It is general to obtain manganese dioxide having a high crystallinity and therefore a high hardness by carrying out electrolysis with a small size.

However, this type of manganese dioxide has a problem that it takes a long time to pulverize and it is impossible to prevent impurities from being mixed in during pulverization. When it is used as a positive electrode material for a battery, the performance of the battery deteriorates due to the mixed impurities. Therefore, improvement has been desired.

Further, manganese dioxide having higher conductivity is desired as a positive electrode material for batteries.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to obtain a high-performance γ-type manganese dioxide which is easy to pulverize, has high conductivity, and has excellent discharge characteristics when used as a positive electrode material for batteries. .

[0007]

DISCLOSURE OF THE INVENTION The inventors of the present invention have conducted an earnest research based on the finding that it is desirable to incorporate carbon fibers or graphite fibers more strongly in manganese dioxide crystals in order to achieve the above-mentioned object. As a result of stacking, short fibers of carbon fibers or graphite fibers provided with a film of manganese oxide on the surface are dispersed in a manganese electrolytic solution, and the above objects are achieved by co-depositing the short fibers with manganese dioxide by electrolysis. As a result, they have completed the present invention.

That is, in the present invention, by providing a manganese oxide film on the surface of the short fibers, 0.1 to 5.
It is possible to firmly incorporate 0% of the short fibers into the manganese dioxide crystals by eutectoid.

The present invention will be described in detail below.

To form a manganese oxide film on the surface of short fibers, M _n (NO ₃ ) ₂ , M _n SO ₄ , M _n3 (PO ₄ ) ₂ , M _n (SO
₄ ) It is sufficient to immerse the short fibers in an aqueous solution of ₃ , ₃ , M _n PO ₄ , M _n (SO ₄ ) ₂ or the like for a few seconds to 10 minutes, and then to heat them to 120 to 400 ° C. for a few minutes to a dozen minutes. Of these manganese compounds, M _n (NO ₃ ) ₂
Is more preferable because it decomposes to easily form an oxide film. When _Mn (NO ₃ ) ₂ is used, the short fibers are immersed in a 0.2 to 9 M _Mn (NO ₃ ) ₂ aqueous solution at room temperature to 90 ° C for 1 to 10 minutes, and 120 to 400
It is preferable to heat at a temperature of ℃ for about 5 minutes.

The carbon fibers or graphite fibers used in the present invention may be known ones such as PAN type, pitch type, rayon type and phenol type, but it is more preferable to use short fibers having a fiber length of 5 to 1000 μm. . If the fiber length exceeds the above upper limit, the dispersion in the manganese electrolyte is difficult. By co-depositing the short fibers, the γ-type manganese dioxide obtained by the present invention has excellent conductivity. It is also effective if the fiber length is near the above lower limit, but it is difficult to obtain economically inexpensive one at present.

The amount of the short carbon fibers or graphite fibers added to the manganese electrolyte is preferably 0.1 to 10 g / l. If the amount added exceeds the upper limit, uniform dispersion in the manganese electrolyte is difficult, and if the amount is less than the lower limit, the amount of short fibers incorporated by eutectoid decreases.

The manganese electrolyte used in the present invention is M _n SO 4.
Ordinary electrolyte such as ₄ / H ₂ SO ₄ , M _n Cl ₂ / HCl may be used. The electrolysis temperature may be 85 to 98 ° C and the current density may be 0.3 to 2.0 A / dm ^2. It is desirable to adjust the amount depending on the amount of fiber added.

[0014]

Since the present invention uses short fibers of carbon fibers or graphite fibers provided with a manganese oxide film on the surface, when electrolyzing in an electrolyte solution of a manganese salt aqueous solution, the β-type M is first formed on the surface of the short fibers. _n O ₂ is present, since the wettability has hydrophilicity is improved, short fibers EMD (gamma-type M _n O ₂₎ in an amount sufficient EMD (gamma-type as well as co-deposited in M _n O _It is easily incorporated into the crystal of ₂ ).

Therefore, the γ-type manganese dioxide obtained by the method of the present invention has a high purity with an M _n O ₂ content of 90% or more, but 0.1 to 5.0% of carbon or graphite is contained in the crystal in a fibrous form. Since it is built in, it can be crushed relatively easily. Further, due to the presence of fibrous carbon or fibrous graphite, the electric conductivity is also good.

On the other hand, when this γ-type manganese dioxide is used in a battery, a battery having excellent performance can be obtained as shown in the following examples. Further, according to the present invention, highly conductive γ-type manganese dioxide can be obtained, so that it becomes possible to manufacture a battery using a positive electrode material in which the blending ratio of a conductive material (graphite powder, acetylene black, etc.) is reduced from the conventional one.

[0017]

Example 1 Pitch-based carbon fibers (graphite) having a fiber diameter of 13 μ and a fiber length of 130 μ were immersed in a 5M- _Mn (NO ₃ ) ₂ solution at room temperature for 5 minutes, and then 200
By thermal decomposition has been applied a coating of β-type M _n O ₂ in ° C..

Then, this was added to 1M-M _n SO ₄ /0.4MH ₂ SO ₄ electrolyte solution at a rate of 2.5 g / l, and γ was added by using the apparatus shown in FIG.
Type manganese dioxide was synthesized.

[0019] The electrolysis apparatus includes a DC power supply 1, a carbon steel cathode plates 2, 2 ', T _i made anode plate 3, a gas blowing tube 4, Hg
/ Hg ₂ SO ₄ Conductive wire 5 to the reference electrode, emitted gas recirculation condenser 6, magnet stirrer 7, and electrolytic cell body 8
It consists of The electrolytic solution 9 to which the short fibers have been added is electrolyzed, and γ-type manganese dioxide having carbon fibers co-deposited on the anode is produced.

In this example, the electrolytic solution 9 was maintained at 90 ° C. or higher and electrolysis was carried out by applying a current density of 1.0 A / dm ² to obtain electrolysis to obtain γ-type manganese dioxide of the present invention. The characteristics are shown in Table 1.

Then, a battery performance test of the obtained γ-type manganese dioxide was conducted by the apparatus shown in FIG. The apparatus shown in FIG. 2 includes a platinum ring anode 10, a pressure transmitter 11, a porous desk 12, a filter paper 13,
The structure is such that the platinum plate 14 for the cathode and the lead wire 15 to the Hg / HgO / 9M-KOH reference electrode are provided in the cell outer shells 16 and 16 '.

Γ-type manganese dioxide obtained in this example
1 g of coke powder, 1 g of coke powder, and 2 g of graphite powder were mixed and placed on a platinum plate for cathode and pressed at a pressure of 700 kg / cm ^{2 to} obtain a cathode material 17. Then, using 9M-KOH as an electrolyte, a continuous discharge of 0.5 mA was performed.

The results are shown in Table 1.

Examples 2 to 4 and Comparative Example 1 PAN-based carbon fibers (carbonaceous) having a fiber diameter of 7 μm and a fiber length shown in Table 1 were added with M _n O ₂ in the same manner as in Example 1, Then, in the same manner as in Example 1, production of electrolytic manganese dioxide and battery performance test were performed. The results are shown in Table 1.

Examples 5 to 6 The same short fibers as used in Example 1 were coated with various manganese oxide films by the treatment shown in Table 1 and then electrolytically oxidized in the same manner as in Example 1. Manganese production and battery performance tests were performed. The results are shown in Table 1.

Comparative Example 2 γ-type manganese dioxide obtained by a commercially available electrolytic method was subjected to a battery performance test in the same manner as in Example 1. The results are shown in Table 1.

Comparative Example 3 The same procedure as in Example 1 was used to produce electrolytic manganese dioxide and batteries using the apparatus shown in FIG. A performance test was conducted. The results are shown in Table 1.

Comparative Example 4 An electrolytic manganese dioxide was prepared and a battery performance test was conducted in the same manner as in Example 1 except that acetylene black was used instead of the short fibers. The results are shown in Table 1.

[0029]

[Table 1]

[Brief description of drawings]

FIG. 1 is an explanatory view showing an example of an electrolysis device for obtaining γ-type manganese dioxide of the present invention.

FIG. 2 is an explanatory diagram showing an example of an apparatus used for a battery performance test using the γ-type manganese dioxide of the present invention.

Claims (2)

[Claims] 1. M _n O ₂ obtained by dispersing short fibers such as carbon fibers or graphite fibers having a manganese oxide coating on the surface in a manganese electrolytic solution, and causing the short fibers to co-deposit with manganese dioxide by electrolysis. A method for producing high-performance γ-type manganese dioxide having a content of 90% by weight or more. Wherein the staple fibers of the carbon fibers or graphite fibers having a coating of manganese oxide on the surface dispersed in a manganese electrolyte, M _n O of the said short fibers obtained by co-precipitating the manganese dioxide by electrolysis ₂ Batteries using γ-type manganese dioxide with a content of 90% or more as the positive electrode material.