JPS58225565A - Alkaline battery - Google Patents

Abstract

PURPOSE:To suppress the generation of hydrogen gas from a negative electrode material effectively as well as to reduce the content of mercury by using a battery negative electrode active material made of amalgamated zinc powder containing indium. CONSTITUTION:At least one type of amalgamated metal powder made of amalgamated zinc powder containing indium and zinc-lead alloy powder is used as a battery negative electrode active material. This active material can suppress the gas generation equally or more effectively than the conventional one and also the battery characteristic can be improved even if the mercury content ratio is lowered to 1% or less. Practically, the negative electrode active material with the mercury content ratio of about 5% or less has a sufficiently larger effect than the active material made of conventional amalgamated zinc powder. The indium content ratio can be as little as 0.01-10%, although some differences exist depending on the production method of said negative electrode active material.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to alkaline batteries using improved cathode active materials and methods of making the same.

In alkaline batteries using zinc as a cathode active material, the battery must be sealed tightly because a strong alkaline electrolyte such as an aqueous potassium hydroxide solution is used. Sealing the battery is especially important when trying to downsize the battery.
At the same time, hydrogen gas generated by corrosion of zinc during battery storage is trapped. Therefore, during long-term storage, the scum pressure inside the battery increases, and the more completely the battery is sealed, the greater the risk of explosion. As a countermeasure against this problem, various efforts have been made to selectively guide the generated gas to the outside of the battery by devising the structure of the battery, but these efforts are still not perfect. Therefore, research has been conducted to prevent corrosion of the zinc cathode active material itself to reduce gas generation inside the battery, and amalgamated zinc, which utilizes the hydrogen overvoltage of mercury, has been exclusively used as the cathode active material. However, the cathode active materials of alkaline batteries commercially available today contain a large amount of mercury, about 5 to 15 mercury, which poses a danger to humans and other living organisms and poses a great risk of environmental pollution.

Therefore, a method has also been proposed in which gas generation is suppressed without using mercury, but instead using a zinc electrode to which PB or the like is added. However, although such elements have a gas generation suppressing effect to some extent, they are currently far from being able to replace mercury. It has been proposed that zinc powder be immersed in an acidic solution containing mercury ions to which PB ions, CD ions, etc. have been added to perform amalgamation using the substitution method, and at the same time, PB and CD be added to the zinc powder.
Even with this method, it is not possible to reduce the mercury content while effectively suppressing gas generation.

In view of the above-mentioned current situation, the present invention provides an alkaline battery using a novel cathode active material that significantly reduces the content of mercury necessary to suppress hydrogen gas generation from the cathode active material and also improves battery characteristics. This is a book that aims to provide. 9 The present inventors have discovered that when indium is present in addition to mercury in a negative electrode active material made of zinc, mercury and indium act synergistically to suppress gas generation, and the amalgamation that has been conventionally used We have discovered that even if the amount of mercury is significantly reduced compared to that in a negative electrode active material made of zinc, it still has a gas generation suppressing effect equal to or better than that of the amalgamated zinc, and also has good battery characteristics, and has led to the present invention. Ta. Regarding the synergistic effects of mercury and other elements, it has been found that there are some that have a synergistic effect with mercury, some that have no effect on the effects of mercury alone, and some that have the effect of canceling out the effects of mercury. Among compounds that have a synergistic effect, such as indium and thallium, we have obtained the knowledge that indium has the greatest effect. Thus, according to the present invention, there is provided an alkaline battery using a cathode active material for a battery made of amalgamated zinc powder containing indium.

While the conventional cathode active material consisting of simply amalgamated zinc powder has a mercury content of 5 to 15%, the active material used in the alkaline battery of the present invention has a mercury content of 1 inch or less. However, gas generation can be suppressed to a greater degree than conventional products, and battery characteristics can also be improved. Of course, it is also possible to increase the mercury content and improve the function of the cathode active material accordingly. Practically, the cathode active material used in the alkaline battery of the present invention has a mercury content of about 5% or less and has a sufficiently greater effect than the conventional active material made of amalgamated zinc powder. Further, the content of indium may vary slightly depending on the method of manufacturing the cathode active material, but it may be present in a small amount of 0.01 to 10%.

The battery cathode active material used in the alkaline battery of the present invention is:
It can be produced by a variety of methods, including (1) amalgamation of zinc-substituted indium powder; (2) amalgamation of zinc powder with indium amalgam;
Alternatively, (3) it is preferable to produce by amalgamating a zinc-indium alloy powder to form a zinc-indium-mercury powder as an amalgamated metal powder.

The first production method is carried out, for example, as follows: Indium or an indium compound is dissolved in an acid such as hydrochloric acid, and in some cases, most of the remaining acid is evaporated by heating, and then this is dissolved in water. An indium salt aqueous solution having a predetermined indium concentration (for example, an indium concentration of 0.1 to 5'h) is prepared by diluting the indium salt with water. Next, zinc powder is immersed in the solution and reacted at a reaction temperature of 80° C. or less for a reaction time of 1 to 60 minutes to adhere indium to the surface of the zinc powder.

By changing the indium concentration in the indium hot water solution, reaction temperature, reaction time, etc., the amount of indium deposited on the zinc powder can be freely changed.

After washing the zinc-indium powder with indium attached to the surface of the zinc powder, it is dried or undried and subjected to amalgamation.

Although amalgamation can be carried out in various ways, the following method is preferred. That is, the above zinc-indium powder is added to an alkaline solution such as an aqueous potassium hydroxide solution, and preliminary stirring is performed for 1 to 60 minutes. Next, while gradually dropping metallic mercury into the above liquid through the small hole,
After stirring for a minute, the mixture is washed with water and dried at a low temperature of 60 to 60°C to obtain a zinc-indium-mercury powder. The preferred indium content of the zinc-indium-mercury powder obtained by this first method is 0.01 to 1 inch.

A second method is to first mix indium and mercury to form an indium amalgam, and then use this indium amalgam to amalgamate zinc powder.
Both are possible. Since mercury has the property of easily forming amalgam not only with zinc but also with indium at room temperature, when zinc powder is amalgamated with indium amalgam, the indium/mercury ratio in indium amalgam is maintained as it is and the amalgam is formed. is contained in zinc powder. Therefore, by changing the indium content in the indium amalgam, the indium and mercury content in the zinc powder can be freely changed. Amalgamation can be done in a variety of ways, but it's good! , (Same as described above, i.e. the zinc powder is amalgamated by adding indium amalgam to the alkaline solution charged.) The zinc-indium-mercury powder produced according to this second method is The preferred indium content is between o, oi and 5.

Furthermore, a zinc-indium alloy powder may be prepared by such means as adding indium to molten zinc, and this alloy powder may be amalgamated to form a zinc-indium-mercury powder.

Various methods can be applied for amalgamation, but preferably the same method as described above, i.e.
Mercury is added to an alkaline solution containing zinc-indium alloy powder. The preferred indium content of the zinc-indium-mercury powder obtained by this method is o-oi~
It is 10%.

Incidentally, even if a zinc-lead alloy powder is used instead of the zinc powder, the above-mentioned method is also completely acceptable.

Hereinafter, the present invention will be explained in more detail with reference to Examples.

Example 1 After completely dissolving 0.3 g of indium in excess hydrochloric acid, most of the remaining hydrochloric acid was removed by thermal evaporation. Next, it was diluted with pure water to 6007 to give an indium concentration of 0.
．． A 5 g/l indium chloride solution was prepared. Add 35 to 100 meters of commercially available zinc powder for batteries to the solution.
g and stirred at 20° C. for 60 minutes to adhere indium to the surface of the zinc powder. The obtained zinc-indium powder was washed with pure water. Next, the zinc-indium powder was added to 1 t of a 10% potassium hydroxide solution prepared in advance, and preliminarily stirred at 20°C for 5 minutes. Next, amalgamation was carried out by stirring at 20° C. for 60 minutes while gradually dropping metallic mercury in an amount corresponding to the desired mercury content through the pores. After the amalgamation was completed, it was washed with water and dried at 45°C for a day and a night. In this way, zinc with an indium content of 0.1% and a mercury content of 1%, 6%, 5%, and 7%, respectively.
Indium-mercury powder was obtained.

Example 2 An indium amalgam having an indium ratio of 10 was prepared by mixing 0.5679 I/dium and 5 g of mercury.

Next, using this indium amalgam, zinc powder was amalgamated in the same manner as in Example 1 to obtain a zinc-indium-mercury powder with an indium content of 0.1% and 1 g of mercury. After preparing an indium amalgam with an indium ratio of 50, it was amalgamated in the same manner as in Example 1 to obtain a zinc-indium-mercury powder with an indium content of 1% and a mercury content of 1q6.

Example 6 Indium is added to molten zinc so that the indium ratio is 0
．． A 1% zinc-indium alloy powder was prepared. This zinc-indium alloy powder was amalgamated using mercury in the same manner as in Example 1 to obtain a zinc-indium-mercury powder having an indium content of 0.1% and a mercury content of 1:1. Further, after adding indium to the molten zinc-lead alloy to prepare a zinc-lead-indium alloy powder with a lead content of 0.1% and an indium content of 0.1%, amalka melon was prepared in the same manner as in Example 1. , the lead content [,1
, 1 section, indium content IJ, 1%, mercury content 1L
% scolded lead-indium-mercury powder was obtained.

A hydrogen gas generation test was conducted using the zinc-indium-mercury powder and the zinc-lead-indium-mercury powder obtained as described above as cathode active materials.

As a comparative example, the same test was conducted using conventionally used zinc-mercury powder (mercury content: 1, 3, 5, 7%) as the cathode active material.

The gas generation test was conducted using 40% by weight hydroxyl as an electric vinegar solution.
5 ml of aqueous solution of hypotassium saturated with zinc oxide
using the above cathode active materials at a temperature of 4
It was carried out at 5°C. From the results shown in Table 1 below, the cathode active material containing indium according to the present invention requires less mercury than the conventional cathode active material to achieve a certain level of gas generation suppression. It is understood that this has significantly decreased.

Next, a battery characteristic test was also conducted on the above-mentioned cathode active material.

The test cell used here was constructed by mixing 10 parts by weight of graphite with 90 parts by weight of a general commercially available manganese dioxide powder aggregate, press-molding the mixture, and then charging the mixture with a separator, a cathode active material, and an electrolyte. The cathode active material was charged in an amount of 65 parts by weight, and the electrolyte was a 40% potassium hydroxide aqueous solution saturated with zinc oxide.

Using these alkaline manganese discharge test cells, a final voltage of 0.0 was obtained under discharge conditions at a discharge load of 20Ω and a temperature of 20°C.
Discharge duration up to 9 V compared to conventional cathode active materials
It was evaluated using the index. The results are shown in Table 2.

Table 2 From the results in Table 2, it can be seen that the cathode active material containing indium according to the present invention has battery characteristics that are equivalent to or better than conventional cathode active materials even if the amount of mercury is significantly reduced. be done.

Patent applicant Mitsui Kinzoku Mining Co., Ltd. Agent Patent attorney Tatsuo Ito Agent Patent attorney Tetsuya Ito 1 Ami Sho 58-225565 (5) ・(

Claims (1)

[Scope of Claims] 1. An alkaline battery characterized in that at least one amalgamated metal powder consisting of an amalgamated zinc powder containing indium and a zinc-lead alloy powder is used as a cathode active material for the battery. 2 The indium content of the amalgamated metal powder is 0
．． The alkaline battery according to item 1 above, with a weight ratio of 01 to 10. 3. The mercury content of the amalgamated metal powder is 5% by weight.
The alkaline battery according to item 1 or item 2, which is as follows. 4 The mercury content of the amalgamated metal powder is 1 weight -
The alkaline battery according to item 6, which is as follows. 5. Adhere indium to the surface of zinc powder or zinc-lead alloy powder, and amalgamate the thus obtained zinc-indium powder or zinc-lead-indium powder to produce zinc-indium-mercury powder or zinc-lead-indium powder. A method for producing an alkaline battery, comprising forming mercury powder as an amalgamated metal powder, and then using the thus formed amalgamated metal powder as a cathode active material for a battery. 6. An alkali, characterized in that zinc powder is amalgamated with indium amalgam to form a zinc-indium-mercury powder as an amalgamated metal powder, and then the amalgamated metal powder thus formed is used as a cathode active material for a battery. Battery manufacturing method. 7. Zinc-indium alloy powder is amalgamated to form zinc-indium-mercury powder as amalgamated metal powder, and the amalgamated metal powder thus formed is then used as a cathode active material for a battery. Alkaline battery manufacturing method. 8. The alkaline battery manufacturing method according to any one of items 5 to 7, using a zinc-lead alloy instead of the zinc.