JPS63248068A - Zinc alkaline battery - Google Patents

Abstract

PURPOSE:To remarkably reduce an amalgamation rate of the negative electrode of a zinc alkaline battery by using a kind selected from a group of a specific saturated monocarboxylic acid and a salt obtained by neutralizing it with alkali metal as the corrosion inhibitor of a negative active material. CONSTITUTION:At least a kind selected from a group of a specific saturated monocarboxylic acid indicated in the formula RCOOH and a salt obtained by neutralizing it with alkali metal is used as the corrosion inhibitor of the negative electrode of a zinc alkaline battery in which alkaline aqueous solution mainly comprising potassium hydroxide or sodium hydroxide is used as electrolyte, zinc or zinc alloy as negative active material, and manganese dioxide, silver oxide, oxygen, nickel oxyhydroxide, or mercuric oxide as positive active material. Thereby, the corrosion resistance of zinc negative electrode is increased and the zinc alkaline battery in which an amalgamation rate is low and practicality is high can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention uses zinc as a negative electrode active material, an alkaline aqueous solution as an electrolyte, and manganese dioxide, silver oxide, or silver oxide as a positive electrode active material.
The present invention provides an effective means for reducing the amount of mercury used to freeze the zinc negative electrode of a zinc alkaline battery using mercury oxide, oxygen, nickel oxyhydroxide, or the like.

Conventional technology In order to suppress the corrosion of the electrolyte of the zinc negative electrode, 7
A method of adding about 10% by weight of mercury to zinc has been adopted industrially. However, in recent years, there has been a growing social need to reduce mercury content in order to reduce pollution, and various corrosion-resistant zinc alloys have been developed or proposed to ensure sufficient corrosion resistance with the use of small amounts of mercury. ing. For example, corrosion-resistant zinc alloy powder, which is made by adding indium, lead, gallium, aluminum, etc. to zinc, is considered to be effective. Zinc alloys containing indium and lead have already been put into practical use, and in order to further improve corrosion resistance, indium, A zinc alloy to which aluminum and, if necessary, gallium are added in addition to lead is being considered as a typical example. When these corrosion-resistant zinc alloys are used, corrosion resistance can be ensured even if the hydration rate (weight percentage of mercury in negative electrode zinc) is reduced; in the case of zinc alloys containing indium and lead, the hydration rate is 3%, Furthermore, in the improved zinc alloy mentioned above, in which aluminum is added in addition to indium and lead, and gallium is added as necessary, even a 1.5% filtration rate is equivalent to 7 to 10% of the filtration rate of pure zinc. Provides corrosion resistance. As seen in the above example, it is effective to use a corrosion-resistant zinc alloy as a method to reduce the hydration rate, but another effective method is to add anti-corrosion agents. The combination of corrosion-resistant zinc alloy and anti-corrosion agent is considered to be essential as a technology to reduce the amount to the utmost limit.

Conventionally, glycols such as ethylene glycol, mercaptocarboxylic acid, aminonaphthalene sulfonic acid, azonaphthalenes, and carbazole have been used to prevent corrosion of zinc negative electrodes in alkaline aqueous electrolytes.

Application of various anticorrosive agents has been proposed, including cyanohydrin, thiazole derivatives such as 2-meltocaptobenzothiazole, and derivatives of penzotriazole. The general application method is to add a small amount of these anticorrosive agents to the electrolyte. However, none of the anticorrosive agents has been found to have a significant anticorrosive effect, and currently they are not effective means for reducing the hydration rate.

Problems to be Solved by the Invention If the corrosion protection of the zinc negative electrode is insufficient, hydrogen gas will be generated as the zinc is consumed during storage of the battery, and the internal pressure of the battery will increase, causing leakage of electrolyte and deformation of the battery. In severe cases, it may cause the battery to explode. Furthermore, corrosion of zinc also causes deterioration in battery performance after storage, such as a decrease in battery capacity. The object of the present invention is to ensure sufficient corrosion resistance of a zinc negative electrode to prevent the occurrence of the above-mentioned problems while minimizing the corrosion rate. As a method of achieving this, the anti-corrosion effect is greater than the various anti-corrosion agents previously proposed.
We have searched for a new anticorrosive agent that is resistant to alkali and has no negative impact on discharge performance, and applied it to batteries with zinc negative electrodes with low hydration rates. The present invention provides a low-pollution zinc-alkaline battery with low energy consumption.

Means for Solving the Problems The present invention uses an alkaline aqueous solution containing potassium hydroxide, sodium hydroxide, etc. as the main components as an electrolyte, and zinc and zinc as the negative electrode active material.
Or zinc alloy, manganese dioxide, silver oxide as positive electrode active material,
So-called zinc alkaline salts using oxygen, nickel oxyhydroxide, mercury oxide, etc.
At least one selected from the group K, RCOON a, and RCOOL i is used.

These anticorrosive agents can be applied by adding them into an electrolytic solution, impregnating both or one of a separator and a liquid retaining material, and attaching them to the surface of a negative electrode active material. Moreover, the above-mentioned anticorrosive agent preferably has 4 to 17 carbon atoms in the alkyl group (R). Furthermore, although pure zinc or a zinc alloy is used as the negative electrode active material, it is particularly effective to use a corrosion-resistant zinc alloy and the above-mentioned anticorrosive agent in combination to achieve a significant reduction in the hydration rate.

For example, when used in combination with a zinc alloy containing indium and lead, or a zinc alloy containing gallium, 0.2%
A battery with sufficient corrosion resistance of the negative electrode can be obtained even at a oxidation rate of
If a zinc alloy containing at least one type of nickel is used in combination, the corrosion resistance of the negative electrode can be ensured even at a 0.05% oxidation rate.

Effect The mechanism of action of the anticorrosive agent used in the present invention is unclear, but is presumed to be as follows.

The anticorrosive agent of the present invention has a nearly linear molecular structure, and has a carboxyl group as a polar group at one end and a hydrophobic alkyl group at the opposite end, and when dissolved in an electrolyte, the polar group becomes a negative electrode. It is thought that the zinc or zinc alloy surface is adsorbed on the surface of the zinc or zinc alloy. The corrosion reaction of zinc in an alkaline electrolyte is shown by the following equation. When the anticorrosive agent is adsorbed to the negative electrode surface and forms a film, the anodic reaction Zn+40H-Zn(o)() Ni+
2e-ka-)” reaction 2H20+2e--20H-+
Hydroxide ions, which cause the H2 anode reaction, are prevented from approaching the zinc negative electrode, and water molecules necessary for the cathode reaction cannot exist near the surface of the zinc negative electrode, thereby suppressing zinc corrosion. Even if the amount of anticorrosive agent is small and does not completely cover the surface of the zinc negative electrode, the corrosion reaction of zinc at the adsorbed portion of the surface of the zinc negative electrode where the added anticorrosive agent is adsorbed is suppressed, and the total amount of corrosion of the zinc negative electrode is reduced.

Furthermore, even if the anticorrosive agent is added by impregnating the separator and/or liquid retaining material, or attaching it to the surface of the negative electrode active material, the anticorrosive agent will be dissolved or dispersed in the electrolyte after battery construction, and the same effect as above will occur. Adsorbs to the surface of the zinc negative electrode, suppressing zinc corrosion. As described above, it is thought that the anticorrosive agent used in the present invention has an anticorrosive effect because it covers the surface where the corrosion reaction of zinc occurs.

In addition, a zinc alloy containing indium and lead disclosed in JP-A-68-18266, or JP-A-60-175
368. JP 61-77267, @81-181 Sho 81
088. Japanese Patent Publication No. 61-203563. Special application 1986-15
Contains indium and lead disclosed by the inventors in 0307 etc., and further contains gallium, aluminum, strontium,
All zinc alloys containing one or more selected from the group of calcium, magnesium, barium, and nickel have excellent corrosion resistance, but sufficient corrosion resistance cannot be ensured when the hydration rate is reduced to about 0.2%. However, when the above-mentioned anticorrosive agents are used in combination, the anticorrosion effects of both are combined, and in some cases, the corrosion resistance of the negative electrode is ensured even at a hydration rate of O and OS%.

As mentioned above, the present invention has experimentally investigated the corrosion inhibitor that is effective in improving the corrosion resistance of zinc negative electrodes, the differences in their molecular structures, and the use of them in combination with corrosion-resistant zinc alloys, and has completed a highly practical zinc-alkaline battery with a low bushing rate. This is what I did.

This will be explained in detail below using examples.

Examples Example 1 First, the corrosion inhibiting effect of the anticorrosive agent of the present invention on zinc in an alkaline solution was investigated. The experimental method was to dissolve the anticorrosive agent of the present invention or the conventional anticorrosive agent in an electrolytic solution containing zinc oxide in a 40% by weight aqueous potassium hydroxide solution to almost saturation level, take 5d, and then freeze in the solution. Zinc powder was added 1 of 1, and the amount of hydrogen gas generated over 20 days at a temperature of 46° C. was measured.

The hydration rate of zinc hydrate powder is 1.0 cm, and the particle size is 35-160
It was a mess. The measurement results obtained are shown in Table 1.

Table 1 In Table 1, groups 1 to 17 using the anticorrosive agent of the present invention are groups 18 to 2 using conventionally proposed anticorrosive agents.
It can be seen that the amount of hydrogen gas generated was smaller than that of the 00 group and Kei 21 to which no anticorrosive agent was added, indicating that the corrosion inhibiting effect of the anticorrosive agent of the present invention is large. Among the melons 1 to 17, Kei 1 to 4 unified the number of carbon atoms in the alkyl groups of the anticorrosive agents to 11, and examined the difference in the anticorrosion effect due to neutralization with an alkali metal. , there is no significant difference between them.

Melon Nos. 5 to 11 are results of examining the anticorrosion effects of various saturated monocarboxylic acids with different numbers of carbon atoms in the alkyl group. Among them, Black Nos. 1 and /E, and Nos. 5 to 11 are the conventional examples of Liao Nos. 18 to 21 or none. The amount of hydrogen gas generated is overwhelmingly smaller than in the case of addition, and it is judged that the number of carbon atoms in the alkyl group is preferably 4 to 17. Also, in the case of alkali metal salts, the number of carbon atoms in the alkyl group is 4.
It is clear that the group of melons 12-17 and 418-21 are effective.

Example 2 Next, based on the results obtained in Example 1, a typical anticorrosive agent was selected, and a button-shaped silver oxide battery was prepared, with the effect of reducing the corrosion rate of zinc or zinc alloy, which is the negative electrode active material, shown in the figure. We made a prototype and compared it.

In the figure, reference numeral 1 denotes a sealing plate made of stainless steel, the inner surface of which is plated with copper. 2 is 40 of potassium hydroxide
An electrolytic solution in which zinc oxide is saturated in a wt% aqueous solution (if an anticorrosive agent is added, an electrolytic solution in which a saturation amount of the anticorrosive agent shown in Table 2 is dissolved) is gelled with carboxymethyl cellulose, and a starch is added to the gel. 60-1 of zinc or glazed zinc alloy
This is a zinc negative electrode in which 50 mesh powder is dispersed. 3 is a cellulose-based liquid retaining material, 4 is a separator made of porous polypropylene, 6 is a positive electrode made of a mixture of silver oxide and graphite and pressure molded, 6 is a positive electrode ring made of iron plated with nickel, 7
is a nickel-plated stainless steel cathode can. A polypropylene gasket 8 is compressed between the positive electrode can 7 and the sealing plate 1 by bending the positive electrode can 7. The prototype battery has a diameter of 11.6W and a height of 5.4cm.

Table 2 shows the changes in the discharge performance and total height of the prototype batteries after they were stored at 60° C. for one month, and the number of batteries in which leakage was observed by visual inspection. The discharge performance was expressed as the discharge duration when discharging at 610Ω at 20° C. with a final voltage of 0.9V.

21st! Normally, in normal button batteries, the total height of the battery decreases slightly over time after the battery is sealed until the stress relationship between each battery component stabilizes, but hydrogen gas is generated due to corrosion of the negative electrode zinc. In batteries with a large number of batteries, the total height of the stain pond tends to increase as the internal pressure of the battery increases. Therefore, the corrosion resistance of the zinc negative electrode can be evaluated based on the change in total height of the battery during storage. A battery with insufficient corrosion resistance not only increases the total height of the battery, but also tends to leak due to an increase in battery internal pressure, and also deteriorates discharge performance due to the consumption of negative electrode zinc due to corrosion and oxidation of the surface.

From this point of view, the prototype experiment results shown in Table 2 are evaluated as follows. First, /E, 1 to 7 have extremely good corrosion resistance as negative electrode active materials, and usually, if the corrosion rate is 1.5 or more,
The battery is constructed using a zinc alloy (a zinc alloy containing Pb, In, and At), which has an extremely low aging rate of 0.05% and is expected to be used as a negative electrode in practical batteries without the aid of anticorrosive agents. This is a comparison of the effects of anticorrosive agents. These results show that cases 1 to 4 in which the anticorrosive agent of the present invention is added are much better than cases 5 to 7 in which conventional corrosion inhibitors are added or not added, and the above corrosion resistance is improved. By using the zinc alloy and the anticorrosive agent of the present invention in combination, it is possible to ensure sufficient corrosion resistance of the negative electrode at a hydration rate of 0.06% or more, indicating that a zinc-alkaline battery with an extremely low aging rate can be constructed. . In addition, black 8 to 14 are currently popular materials with 3
The effectiveness of the anticorrosive agent of the present invention was investigated by reducing the corrosion rate of a zinc alloy (zinc alloy containing Pb and In) which has been put into practical use to 0.2 degrees. . In this case as well, there is a clear difference in battery performance between the examples of Mud 8 to 11 and the conventional examples of /r2.12 to 14 or cases without additives. 0 if used together.
This shows that a zinc-alkaline battery with a low aging rate and excellent practical performance, with sufficient corrosion resistance of the negative electrode, can be constructed with a hydration rate of 2 or more. Furthermore, Kei 15-21 shows that when pure zinc powder, which normally requires a filtration rate of about 7 to 10 cm, is used as the negative electrode active material, the present invention can be applied to reduce the filtration rate to 3%. Full of practicality! This shows that a pond can be constructed.

In addition, in Figures 22 to 33, the effects of the present invention were confirmed to be sure when a zinc alloy with a corrosion rate of 1, 5 to 3 was used for the negative electrode, which could ensure almost the corrosion resistance of the negative electrode without the aid of anticorrosive agents. In the case of the examples of Monodeashi, Otori 22-24 and Eny 28-3o, the characteristics are further improved compared to the conventional examples of &25-27 and Sakazuki 31-33 or the case of no additives, and a high degree of This indicates that the quality has been stabilized by ensuring corrosion resistance.

//i;34.35 investigated the effect of the present invention using a zinc alloy containing Pb, In, and Ga with a corrosion rate of 0.2%, which has almost the same corrosivity as a zinc alloy containing Pb and In. In the case of Example 34, Pb of Melon 8 to 11,
This shows that it is possible to achieve a filtration rate of 0.2%, similar to the example with the zinc alloy containing In.

Mud 35 to 45 are expected to be zinc alloys with corrosion resistance that is almost equivalent to zinc alloys containing Pb, In, and At with improved corrosion resistance, and have a corrosion rate of o, ots%.
The effects of the present invention were investigated in the following examples.
6, 38, 40, 42. 44) also showed excellent battery performance even at low flux rates of o and os%, similar to Examples 1 to 4 using zinc alloys containing Pb, In, and At. It shows. All of the above cases are the results of examining the effects of the present invention by dissolving an anticorrosive agent in the electrolyte, but g46.47
．． 48 shows an embodiment of the present invention other than the method of adding an anticorrosive agent to the electrolytic solution. 47 and 48 in which the anticorrosion agent was impregnated into the electrolyte solution were found to have almost the same effect as when the anticorrosion agent was dissolved in the electrolyte solution. It has an anti-corrosion effect when dissolved in
7) When the filter or liquid-retaining material is impregnated with an anticorrosive agent, the electrolyte penetrates faster, making the battery structure easier and increasing productivity.

Effects of the Invention The present invention has made it possible to significantly reduce the filtration rate of the negative electrode of a zinc-alkaline battery through the effect of a newly discovered anticorrosive agent.

[Brief explanation of the drawing]

The figure is a partially sectional side view of a button-shaped silver oxide battery used in an example of the present invention. 2...Zinc negative electrode, 4...Separator,
5...Silver oxide positive electrode. Name of agent: Patent attorney Toshio Nakao and 1 other person2-
- Itsu Hakusuya 4--1-'e) Mareta 5--Monoxide class positive electrode

Claims (7)

[Claims] (1) Saturated monocarboxylic acid (
A zinc-alkaline battery using at least one selected from the group of RCOOH) and salts thereof neutralized with an alkali metal. (2) The zinc-alkaline battery according to claim 1, wherein the alkyl group (R) of the anticorrosive agent has 4 to 17 carbon atoms. (3) The zinc-alkaline battery according to claim 1 or 2, wherein an anticorrosive agent is dissolved in the electrolyte. (4) The zinc-alkaline battery according to claim 1 or 2, wherein both or one of the separator and the electrolyte holding material is impregnated with an anticorrosive agent in advance. (5) The zinc-alkaline battery according to claim 1 or 2, wherein an anticorrosive agent is previously attached to the surface of the negative electrode active material. (6) A claim in which a zinc alloy containing indium and lead as essential additive elements and gallium as an optional additive element is used as the negative electrode active material, and the filtration rate of the negative electrode active material is 3 to 0.2%. The zinc-alkaline battery according to any one of items 1 to 5. (7) Using a zinc alloy as a negative electrode active material, which contains indium and lead as essential additive elements, and further contains one or more selected from the group of aluminum, strontium, calcium, magnesium, barium, nickel, and gallium;
The zinc-alkaline battery according to any one of claims 1 to 5, wherein the negative electrode active material has a hydrogenation rate of 1.5 to 0.05%.