JPH06150914A - Manganese dioxide for lithium battery and manufacture thereof - Google Patents

Abstract

(57) [Summary] [Objective] Manganese dioxide for a lithium battery, which can improve the discharge voltage and discharge capacity of the primary battery together with the cycle characteristics of the secondary battery, and can impart excellent corrosion resistance, and The manufacturing method is provided. (1) Manganese dioxide for lithium batteries, which has a specific surface area of 80 m ² / g or more and a sulfate ion content of 1% by weight or less. (2) A method for producing manganese dioxide for a lithium battery, which comprises electrolyzing manganese sulfate and a sulfuric acid solution as an electrolytic solution to produce electrolytic manganese dioxide at an electrolysis current density of 130 A / m ² or more.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to manganese dioxide used as an anode active material for lithium primary batteries and lithium secondary batteries (hereinafter collectively referred to as lithium batteries) and a method for producing the same, and particularly to a high specific surface area, The present invention relates to manganese dioxide for lithium batteries, which has a low sulfate ion content, can improve the discharge potential and discharge voltage of the battery, and can also improve the cycle characteristics of the secondary battery, and is excellent in corrosion resistance, and a method for producing the same.

[0002]

2. Description of the Related Art Manganese dioxide is known as a typical anode active material for lithium batteries and has already been put to practical use. Of these, manganese dioxide is used in large quantities especially because it has excellent discharge characteristics and is inexpensive.

At present, lithium primary batteries using this manganese dioxide as an anode active material are used for applications such as cameras. However, batteries having improved discharge voltage are desired due to multifunctionalization of cameras. Further, in this lithium primary battery, extension of discharge capacity, that is, discharge time is also required. On the other hand, lithium secondary batteries are used for applications such as memory backup, but their cycle characteristics, that is, reduction of cycle deterioration are desired.

Conventionally, manganese dioxide used in a lithium battery uses manganese sulfate and a sulfuric acid solution as an electrolytic solution, titanium as an anode, carbon as a cathode, and a bath temperature of 90.
What is electrolyzed under the conditions of ˜100 ° C. and electrolytic current density of 50-100 A / m ² and the electrolytic manganese dioxide deposited on the anode is peeled off, washed, neutralized, dried and heat treated (calcined) is used.

However, the specific surface area of the precipitated electrolytic manganese dioxide is as low as about 20 to 45 m ² / g, and the specific surface area is further reduced by heat treatment for the purpose of dehydration.
It is about 0 to ²⁰ m ² / g. When the specific surface area of manganese dioxide is small, the discharge characteristics of the battery are deteriorated when it is used as an anode active material of a lithium battery. Further, the deposited electrolytic manganese dioxide is γ-manganese dioxide suitable for lithium batteries, but it is changed to β-manganese dioxide by heat treatment. This β-manganese dioxide is inactive as an anode active material and has large cycle deterioration, and is not preferable as manganese dioxide for lithium batteries.

Therefore, in the conventional electrolytic manganese dioxide,
It did not satisfy the discharge characteristics required for lithium batteries.

On the other hand, a general requirement for batteries is that they are resistant to corrosion. Naturally, improvement in corrosion resistance is also required for lithium batteries.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems of the prior art, and can improve both the discharge voltage and the discharge capacity of the battery and the cycle characteristics of the secondary battery. It is also an object of the present invention to provide manganese dioxide for lithium batteries, which can impart excellent corrosion resistance, and a method for producing the same.

[0009]

The above objects of the present invention are achieved by setting the specific surface area of manganese dioxide and the concentration of sulfate ion to be within specific ranges.

That is, the manganese dioxide for lithium batteries of the present invention is characterized by having a specific surface area of 80 m ² / g or more and a sulfate ion content of 1% by weight or less.

In the manganese dioxide of the present invention, the specific surface area is 80 m ² / g or more, preferably 80 to 130 m ² / g.
It is necessary to be. If the specific surface area is less than 80 m ² / g, improvement in discharge voltage and discharge capacity cannot be achieved when used in a battery. The upper limit is not particularly limited, but 150 m
If it exceeds ² / g, manganese dioxide tends to be bulky.
As described above, since the manganese dioxide of the present invention has a high specific surface area, it has a specific surface area of 50 to 100 even after the heat treatment for dehydration.
A high level of m ² / g can be maintained.

Further, the sulfate ion concentration in manganese dioxide must be 1% by weight or less, and if it exceeds 1% by weight, the corrosion resistance becomes poor when used in a battery.

The manganese dioxide of the present invention is a diffraction line in the X-ray diffraction pattern (110) plane: CuKα 2θ = 2.
It is desirable that the Q value [I ₍₁₁₀₎ / I ₍₀₂₁₎ ] which is the diffraction intensity ratio between 2 ° and the (021) plane: CuKα 2θ = 37 ° is 0.80 or less. When the Q value is 0.8 or less, the arrangement of manganese becomes irregular, and so-called ε-type manganese dioxide is obtained. In this case, the crystallinity of β-type manganese dioxide when fired is low, and manganese dioxide suitable for a lithium battery positive electrode active material can be obtained. Therefore, when the Q value is 0.95 or more on average as in conventional electrolytic manganese dioxide,
It will contain a large amount of γ-manganese dioxide. When such manganese dioxide is used, γ-manganese dioxide is changed into β-manganese dioxide having good crystallinity which is inactive as an anode active material by heat treatment, and when used as an anode active material, the discharge characteristics and cycle characteristics of a lithium battery are improved. It will damage.

Next, a preferred method for producing manganese dioxide of the present invention will be described. In the present invention, electrolytic manganese dioxide is obtained under normal electrolysis conditions except for the electrolysis current density. That is, manganese sulfate 1.0 to 1.2 mol / liter, sulfuric acid 0.3 to 0.6 mol / liter, bath temperature 90
Electrolysis is performed under the condition of -100 ° C. Titanium alloy, carbon, lead alloy or the like is used as the anode, and carbon, lead alloy or the like is used as the cathode.

In the present invention, the electrolysis is performed at a high current density of 130 A / m ² or more. By using such a high current density, electrolytic manganese dioxide having a large specific surface area and a sulfate ion concentration of 1% by weight or less can be obtained.

The electrolytic manganese dioxide thus deposited on the anode is washed, neutralized, dried, pulverized and heat-treated for dehydration by a conventional method, and is suitably used as an anode active material of a lithium battery.

[0017]

EXAMPLES The present invention will be specifically described below with reference to examples.

Example 1 A graphite plate was alternately suspended as an anode and a cathode in an electrolysis cell having an internal volume of 5 liters equipped with a heating device, and electrolysis comprising a mixed solution of manganese sulfate and sulfuric acid at the bottom of the electrolysis cell. A replenisher with an addition tube was used.

This replenishing solution was poured into an electrolytic cell, and the composition of the electrolytic solution was manganese sulfate 1.0 mol / liter and sulfuric acid 0.4.
Adjust the bath temperature to be mol / l and the bath temperature is 95 ± 2 ℃.
Electrolysis was carried out at a current density of 150 A / m ² .

After completion of electrolysis, the electrolytic manganese dioxide deposited on the anode was washed, neutralized, dried and pulverized by a conventional method.
The specific surface area of the obtained electrolytic manganese dioxide is 92 m ² /
g, the sulfate ion concentration was 0.64% by weight, and the Q value by the powder X-ray diffraction method using a Cu tube was 0.68.

Next, heat treatment is performed at 400 ° C. for 4 hours,
0.135 g of the obtained manganese dioxide was weighed, mixed with 0.09 g of graphite and 0.06 g of tetrafluoroethylene resin, and press-molded at 3 t / cm ² to obtain an anode mixture. Pre-dried manganese dioxide, graphite and tetrafluoroethylene resin were used.

A test cell as shown in FIG. 1 was prepared by using the obtained anode mix and was stored at room temperature of 20 ° C. for 2500 hours.
A constant resistance continuous discharge test of Ω was performed. These operations are
All were carried out in a dry box under an argon atmosphere. The electrolytic solution used was prepared by dissolving 1 mol / liter of lithium perchlorate in a 1: 1 mixed solvent of propylene carbonate and 1,2-dimethoxyethane. The reagents used in this case were dried after a conventional method. Also,
As the cathode, sheet-shaped metallic lithium was punched out so as to have the same diameter as the anode mixture and used.

Further, in the test cell of FIG. 1, 1 is a cathode terminal for taking out an electric current to the outside, 2 is an insulator made of Teflon resin, and each of them is a screw type so that the cell can be sealed. There is. Further, 3 is a cathode plate, 4 is a sheet-shaped metal lithium (cathode) which is pressure-bonded, 5 is a non-woven separator, 6 is an anode mixture prepared by the above method,
Reference numeral 7 denotes a stainless steel anode, respectively.

Using this test cell, a constant resistance continuous discharge test was conducted as described above, and the relationship between the obtained discharge voltage and discharge duration is shown in FIG.

Example 2 Using the same apparatus as in Example 1, the current density during electrolysis was set to 60.
Electrolysis was performed under the same conditions as in Example 1 except that the amount was changed to 0 A / m ² , followed by the same post-treatment as in Example 1 to obtain electrolytic manganese dioxide. The specific surface area of the obtained manganese dioxide was 122 m ² / g, and the sulfate ion concentration was 0.34.
The Q value by the powder X-ray diffraction method using a Cu tube was 0.72 by weight.

Next, heat treatment was performed under the same conditions as in Example 1, and the obtained manganese dioxide was processed in the same manner as in Example 1 to prepare a test cell similar to that shown in FIG. 1. Using this test cell, 2500 Ω was used. Fig. 2 shows the relationship between the discharge voltage and the discharge duration obtained by conducting the constant resistance continuous discharge test of.

Comparative Example 1 Using the same device as in Example 1, the current density during electrolysis was set to 60.
Electrolysis was performed under the same conditions as in Example 1 except that the amount was changed to A / m ² , and then the same post-treatment as in Example 1 was performed to obtain electrolytic manganese dioxide. The specific surface area of the obtained manganese dioxide was 37 m ² / g, the sulfate ion concentration was 1.17% by weight, and the Q value by the powder X-ray diffraction method using a Cu tube was 0.
It was 92.

Next, heat treatment was performed under the same conditions as in Example 1, and the obtained manganese dioxide was processed in the same manner as in Example 1 to prepare a test cell similar to that shown in FIG. Fig. 2 shows the relationship between the discharge voltage and the discharge duration obtained by conducting the constant resistance continuous discharge test of.

As is clear from the above results, Example 1
The manganese dioxide obtained in any one of Examples 1 to 2 has a larger specific surface area than the manganese dioxide obtained in Comparative Example 1,
The sulfate ion concentration is low and the Q value is low.

Further, as shown in FIG.
No. 2 has a higher discharge voltage than Comparative Example 1, and has a longer discharge duration up to 2V.

Example 3 The manganese dioxide obtained in Example 1 was subjected to the same heat treatment as in Example 1, and the same operation as the test cell shown in FIG. 2 was prepared. However, a lithium-aluminum alloy (aluminum content 15% by weight) was used for the cathode plate.
Using this test cell, a current of 3.8 mA.
Charge and discharge are repeated at a voltage in the range of 0V, 5 cycles, 1
The secondary battery discharge capacities of 0 cycles and 50 cycles were measured, and the results are shown in Table 1.

Example 4 Using the manganese dioxide obtained in Example 2, a test cell similar to that of Example 3 was prepared, the secondary battery discharge capacity was measured according to the method of Example 3, and the results are shown. Shown in 1.

Comparative Example 2 Using the manganese dioxide obtained in Comparative Example 1, a test cell similar to that of Example 3 was prepared, the secondary battery discharge capacity was measured according to the method of Example 3, and the result is shown. Shown in 1.

[0034]

[Table 1]

As is clear from the results shown in Table 1, Examples 3 to
No. 4 shows less decrease in discharge capacity when repeated cycles than Comparative Example 2.

[0036]

As described above, according to the production method of the present invention, the specific surface area is large and the sulfate ion concentration is low,
In addition, manganese dioxide having a low Q value can be obtained.

By using the manganese dioxide of the present invention as the positive electrode active material of a lithium primary battery, the discharge voltage and discharge capacity of the battery can be improved. Further, by using it as an anode active material of a lithium secondary battery, the cycle characteristics of the battery can be improved.
Furthermore, it imparts excellent corrosion resistance to lithium batteries.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of a test cell used in Examples and Comparative Examples.

FIG. 2 is a graph showing the relationship between discharge voltage and discharge duration in Examples and Comparative Examples.

[Explanation of symbols]

1: cathode terminal, 2: insulator, 3: cathode plate, 4: lithium (cathode), 5: separator, 6: anode mixture, 7 anode.

Claims (3)

[Claims] 1. A manganese dioxide for a lithium battery, which has a specific surface area of 80 m ² / g or more and a sulfate ion content of 1% by weight or less. 2. A diffraction line in an X-ray diffraction pattern (11)
0) plane: CuKα2θ = 22 ° and (021) plane: CuK
Q value [I ₍₁₁₀₎ which is the diffraction intensity ratio with α 2 θ = 37 °
/ I ₍₀₂₁₎ ] is 0.80 or less, and the manganese dioxide for a lithium battery according to claim 1. 3. Manganese dioxide for a lithium battery, characterized in that electrolysis is performed using manganese sulfate and a sulfuric acid solution as an electrolytic solution to produce electrolytic manganese dioxide at an electrolysis current density of 130 A / m ² or more. Method.