JPH0513070A - Alkaline battery - Google Patents

Abstract

PURPOSE:To restrain the corrosion of zinc, and hydrogen gas generated therefrom by using a fluorine compound containing the specified hydrogen or alkaline metal, as a corrosion inhibitor for the zinc used as a negative electrode active material. CONSTITUTION:A fluorine compound expressed by the formula is used as a corrosion inhibitor for zinc in a negative electrode material 4 comprising paste zinc as a negative electrode active material. In the formula, M stands for hydrogen or alkaline metal, and (n) means numerals of 2 to 18. In addition, the fluorine compound thereby expressed has a chain structure of parfluoro system. Thus, the compound is stable in alkaline electrolytic liquid, and highly durable to maintain a corrosion inhibiting effect. A positive electrode compound 1 contains manganese dioxide as a positive electrode active material, and is inserted in a positive electrode can 2 after added with crystalline graphite as a conductive assistant and a binder, thereby constituting a battery, together with a separator 3, a negative electrode current collector 5 and the like. According to this construction, state free from mercury can be attained and the corrosion of the zinc can be restrained. Also, hydrogen gas generation from the zinc can be restrained.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an alkaline battery using zinc as a negative electrode active material.

[0002]

2. Description of the Related Art Conventionally, in alkaline batteries using zinc as a negative electrode active material, the surfaces of zinc particles have been amalgamated with mercury in order to suppress generation of hydrogen gas due to corrosion of zinc. And the amount of mercury is
Emphasizing the effect of inhibiting corrosion on zinc, in many cases, the amalgamation rate (blinding rate) reached nearly 10% by weight (for example, "new battery", published by Tokyo Denki University Press, 1978, Page 42).

However, recently, environmental pollution due to mercury has become a problem, and it is required to reduce the amalgamation rate.

Therefore, instead of mercury, indium,
The addition of lead, gallium, aluminum, bismuth, etc. to zinc and alloying with zinc have been studied to suppress the corrosion of zinc. Currently, the amalgamation rate is about 0.10 to 0.15% by weight. It has become possible to reduce to

[0005]

[Problems to be Solved by the Invention] However, in the future,
In order to eliminate mercury, the additive metals that have been proposed so far cannot be said to be sufficient, and organic inhibitors such as lactonitrile and carbazole that have been conventionally proposed as corrosion inhibitors have sufficient effects. It is the current situation that there is no such thing, and it is not an effective means for producing anhydrous silver.

Therefore, the present invention solves the problems that occur in the process of making an alkaline battery using zinc as a negative electrode active material into anhydrous silver, and suppresses the corrosion of zinc without causing environmental pollution, thereby preventing the corrosion of zinc. The purpose is to suppress the generation of hydrogen gas.

[0007]

The present invention provides the following general formula (I) as a corrosion inhibitor for zinc.

[0008]

[Chemical 2]

The above object is achieved by using a fluorine-based compound represented by the formula (wherein M is hydrogen or an alkali metal and n is 2 to 18).

The reason why the corrosion of zinc and the generation of hydrogen gas from zinc can be suppressed by using the fluorine compound represented by the above general formula (I) is not always clear at present. Can be thought of as.

First, the corrosion reaction of zinc proceeds as shown in the following equation.

[Anode] Zn + 4OH ⁻ → Zn (OH) ₄ ²⁻ + 2e [Cathode] 2H ₂ O + 2e → 2OH ⁻ + H ₂

The fluorine-based compound represented by the general formula (I) has a water-repellent C _n F _2n-1 O-C ₆ H ₆ (benzene nucleus) in which its polar group (S-containing group) is adsorbed on zinc. To C ₆ H
₍ Shown in ₆ ) inhibits the affinity between zinc and the electrolyte and reduces the contact area between them, so the above corrosion reaction is suppressed and the generation of hydrogen gas from zinc is suppressed. It is considered to be a thing.

Further, the fluorine-containing compound represented by the general formula (I) is more stable in the alkaline electrolyte than the conventional organic inhibitor since its chain structure part is a perfluoro-type, and has a corrosion inhibiting effect. Excellent sustainability.

In the present invention, the alkali metal represented by M in the general formula (I) showing a fluorine compound used as a corrosion inhibitor includes lithium, sodium, potassium and the like. These alkali metals are easily ionized, and when M is an alkali metal, the solubility of the fluorine-based compound represented by the general formula (I) in the electrolytic solution is better than when M is hydrogen.

In the general formula (I), n is set to 2 to 18 because the effect of suppressing zinc corrosion is not sufficient even if n is smaller than 2 or larger than 18. is there. And as n in this general formula (I), 6-14 are especially preferable.

The fluorine-based compound represented by the general formula (I) can be used by adding the fluorine-based compound represented by the general formula (I) to the electrolytic solution, or by the general formula (I). A method of pretreating zinc with a solution in which a fluorine-based compound is dissolved or dispersed, a method of adsorbing the fluorine-based compound represented by the general formula (I) onto a separator, and the like can be adopted.

The amount of the fluorine-based compound represented by the general formula (I) used is 50 to 5000 pp relative to zinc.
m, particularly preferably in the range of 100 to 1000 ppm.

When the amount of the fluorine-based compound represented by the general formula (I) used is less than 50 ppm with respect to zinc, the effect of suppressing the corrosion of zinc is not sufficiently exerted, and 5
If it is more than 000 ppm, the amount of adsorption on zinc becomes too large, which may cause abnormal discharge.

The present invention is characterized in that the fluorine-based compound represented by the general formula (I) is used as a corrosion inhibitor as described above, but other than that, a usual constitution can be adopted.

For example, zinc as a negative electrode active material includes
Zinc to which indium, lead, gallium, aluminum, bismuth, or the like is added can be used, and as the positive electrode active material, for example, manganese dioxide or the like can be used. As the electrolytic solution, an alkaline aqueous solution such as an aqueous potassium hydroxide solution or an aqueous sodium hydroxide solution can be used, or zinc oxide can be added to the electrolytic solution.

[0022]

EXAMPLES Next, the present invention will be described in more detail with reference to examples. In addition, prior to the Examples, the experimental results are shown as Experimental Example 1 in which zinc was immersed in an electrolytic solution to which various corrosion inhibitors were added, and the corrosion inhibitory effect of zinc by the corrosion inhibitors was examined without using a practical battery. . Such Experimental Example 1 is for avoiding the influence of other constituent materials in the case of being used as a practical battery and accurately grasping the corrosion inhibiting effect of the fluorine-based compound represented by the general formula (I) on zinc. .

Experimental Example 1 Various corrosion inhibitors were added to a 35 wt% potassium hydroxide aqueous solution saturated with zinc oxide used as an electrolytic solution, and zinc powder (containing 500 ppm of lead) was immersed therein at 45 ° C. for 30 days. Then, the amount of hydrogen gas generated during that time was measured. The results are shown in Table 1.

The amount of zinc in the above is 3.5 g, and the amount of the above potassium hydroxide aqueous solution is 2 ml, which are the same as the amount of zinc to be filled in the AA battery and the amount of electrolyte to be injected. And, the amount of corrosion inhibitor is 500 p for zinc.
pm.

Further, in Table 1, zinc containing no mercury (containing 500 ppm of lead) was used, and no corrosion inhibitor was added (no addition), and the amalgamation rate as zinc was 0.15% by weight. The results obtained by similarly examining the amount of hydrogen gas generated in the case of using zinc amalgamated with No. 1 and no corrosion inhibitor (conventional zinc) are also shown.

[0026]

[Table 1]

In Table 1, the sample No. 1-No. The corrosion inhibitor of No. 4 belongs to the fluorine compound represented by the general formula (I). 1-No. When the corrosion inhibitor of No. 4 is used, the amount of hydrogen gas generated is small and the conventional zinc (that is, the conventional amalgamation rate of 0.15% by weight).
The amount of hydrogen gas generated is similar to that of
The corrosion inhibition effect was excellent.

Example 1 As a corrosion inhibitor, C ₆ F ₁₁ O-C ₆ H ₆ -SO ₃ H was added to an electrolytic solution to prepare an AA alkaline battery having the structure shown in FIG. The discharge duration at (final voltage 0.9 V) was examined. The results are shown in Table 2.

The battery shown in FIG. 1 will be described. In the figure, 1 is a positive electrode mixture, and this positive electrode mixture 1 contains manganese dioxide as a positive electrode active material, and phosphorous graphite as a conduction aid and a binder. The mixed material obtained by adding and mixing the above sodium polyacrylate is molded into a ring shape and inserted into the positive electrode can 2 with a terminal.

Reference numeral 3 is a separator, and 4 is a negative electrode agent made of paste zinc. This negative electrode agent 4 contains 500 lead.
Zinc powder with a particle size of 35 to 200 mesh containing 6 ppm
After dry-mixing 0 part by weight and 2 parts by weight of sodium polyacrylate, C ₆ F ₁₁ O-C ₆ H ₆ -SO _{3 was} added as a corrosion inhibitor.
Electrolyte solution containing H (35% by weight saturated with zinc oxide
38 parts by weight of an aqueous solution of potassium hydroxide) was added, and the mixture was stirred and gelled to prepare a paste.

Reference numeral 5 is a negative electrode current collector, 6 is a sealing body, 7 is a metal washer, 8 is a resin washer, 9 is an insulating cap, 10 is a negative electrode terminal plate, and 11 is a resin exterior body.

The zinc filling amount in this battery was 3.5 g.
In, the amount of the electrolytic solution is _{2ml, C 6 F 11 O-} C 6 H 6 -
The added amount of SO ₃ H is 500 ppm with respect to zinc.

Comparative Example 1 An AA alkaline battery was prepared in the same manner as in Example 1 except that C ₆ F ₁₁ O—C ₆ H ₆ —SO ₃ H was not added. That is, the zinc of the battery of Comparative Example 1 does not contain mercury as in the case of Example 1.

Table 2 shows the results of examining the discharge duration of the battery of Comparative Example 1 as in Example 1.

Comparative Example 2 Same as Example 1 except that amalgamated zinc having an amalgamation rate of 0.15% by weight was used and C ₆ F ₁₁ O—C ₆ H ₆ —SO ₃ H was not added. As a result, an AA alkaline battery was produced.

Table 2 shows the results of examining the discharge duration of the battery of Comparative Example 2 as in Example 1.

[0037]

[Table 2]

As shown in Table 2, the battery of Example 1 had the same discharge duration as the battery of Comparative Example 2 using zinc amalgamate, and the discharge characteristics due to the use of the corrosion inhibitor. Was not observed.

[0039]

As described above, in the present invention, by using a fluorine compound represented by the general formula (I) as a corrosion inhibitor for zinc, the corrosion of zinc is suppressed and hydrogen gas from zinc is reduced. Was able to be suppressed.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view showing an example of an alkaline battery according to the present invention.

[Explanation of symbols]

1 Positive electrode mixture 3 separator 4 Negative agent

Claims (2)

[Claims] 1. In an alkaline battery using zinc as a negative electrode active material, as a corrosion inhibitor of zinc, a compound represented by the following general formula (I): (In the formula, M is hydrogen or an alkali metal, and n is 2 to
18) is used, and an alkaline battery is used. 2. The alkaline battery according to claim 1, wherein n in the general formula (I) is 6 to 14.