JPS63248070A - Zinc alkaline battery - Google Patents

Abstract

PURPOSE:To remarkably reduce an amalgamation rate of the negative electrode of a zinc alkaline battery by using at least a kind selected from a group of a specific low-molecular polyacrylic 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 low- molecular polyacrylic acid 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 in hydration of 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 an increasing 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. . For example, corrosion-resistant zinc alloy powder made by adding indium, lead, gallium, aluminum, etc. to zinc is considered to be effective. Zinc alloys containing indium and lead are already in 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 icing rate (weight percentage of mercury in negative electrode zinc) is reduced; in the case of zinc alloys containing indium and lead, the icing 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 filtration rate of about 1.6% is equivalent to a filtration rate of 7 to 10% in the case of pure zinc. Provides corrosion resistance.

As can be seen in the above examples, it is clear that using a corrosion-resistant zinc alloy is effective as a method of reducing the corrosion rate.
Another effective method is to add an anticorrosive agent, and the combination of a corrosion-resistant zinc alloy and an anticorrosive agent is considered essential as a technique for reducing the mercury content in batteries to the utmost limit.

Conventionally, glycols such as ethylene glycol, mercaptocarboxylic acid, amitunaphthalif,
, azonaphthalenes, carbazole.

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

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 corrosion resistance of a zinc negative electrode sufficient to prevent the occurrence of the above-mentioned problems while minimizing the freezing 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 does not have a negative impact on discharge performance, and applied it to batteries with zinc negative electrodes with low corrosion 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, zinc or zinc alloy as a negative electrode active material, and manganese dioxide, silver oxide, or oxygen as a positive electrode active material. , nickel oxyhydroxide.

Low-molecular polyacrylic acid, (E-CH2CH(COOH)), and salts of this neutralized with alkali metals, such as fCH2CH( C
OOK)-),, fCH2CH(COONa),:)
,.

-[CH2CH(COOLi)-), at least one selected from group O is used.

These anticorrosives can be applied by adding them into the electrolyte, impregnating both or one of the separator and liquid retaining material, and attaching them to the surface of the negative electrode active material. The degree (b) is preferably 5 to 60.

Further, pure zinc or a zinc alloy is used as the negative electrode active material, but in order to achieve a particularly significant reduction in the freezing rate, it is effective to use a corrosion-resistant zinc alloy and the above-mentioned anticorrosive agent together. For example, when used in combination with a zinc alloy to which indium and lead are added, or a zinc alloy to which gallium is added, a battery with sufficient corrosion resistance of the negative electrode can be obtained even at a freezing rate of 0.2 inches; If a zinc alloy containing at least one of aluminum, strontium, calcium, magnesium, barium, and nickel is used in addition to the above elements, the corrosion resistance of the negative electrode can be ensured even at a 0.05% filtration 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 carboxyl group, which is a polar group, as a side chain in the main chain of the carbon-carbon bond skeleton structure, and is easily dissolved in an electrolytic solution. It is thought that a portion of the zinc or zinc alloy of the negative electrode 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, and when the anticorrosive agent is adsorbed on the negative electrode surface and forms a film.

7/-de reaction Zn+40H-+$ Zn(OH)4 +
2e force sword reaction 2H20+ 2e-→20H-+
f(2) The approach of hydroxide ions, which cause the anode reaction, to the zinc negative electrode is blocked, and the water molecules necessary for the cathode reaction cannot exist near the surface of the zinc negative electrode, suppressing corrosion of zinc. Corrosion inhibitor Even if the amount of anticorrosion added is small and does not completely cover the surface of the zinc negative electrode, the adsorption of the added corrosion inhibitor on the surface of the zinc negative electrode is
The corrosion reaction of zinc in the Ii portion 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 dissolve or disperse in the electrolyte after battery construction, and the same problem 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-58-18266, or JP-A-60-176
368, JP-A-61-77267° JP-A-61-18
1058. Unexamined Japanese Patent Publication No. 61-203563゜Patent Application No. 61-1
50307 etc., containing indium and lead, and further selected from the group of gallium, aluminum, strontium, calcium, magnesium, barium, and nickel? All of the zinc alloys containing zinc have excellent corrosion resistance, but if the icing rate is reduced to about 0.2 inches, sufficient corrosion resistance cannot be ensured. 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 freezing rate of 0.05%.

As mentioned above, the present invention has developed a highly practical zinc-alkaline battery with a low corrosion rate, based on a practical study of corrosion inhibitors that are effective in improving the corrosion resistance of zinc negative electrodes, differences in their molecular structures, and their use in combination with corrosion-resistant zinc alloys. It is completed.

This will be explained in detail below using suitable 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 11,000 pp of the anticorrosive agent of the present invention or a conventional anticorrosive agent in an electrolytic solution in which zinc oxide was dissolved in a 40 wt. The amount of hydrogen gas generated over 20 days at a temperature of 46°C was measured. The freezing rate of the zinc hydrate powder was 1.0%, and the particle size was 35 to 150 mesh. The obtained measurement results are the first
Shown in the table.

In Table 1, Groups 1 to 140 using the anticorrosive agent of the present invention are group 1 to 140 using the anticorrosive agent of the present invention;
The amount of hydrogen gas generated was smaller than Group 7 and Group 18 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 cases 1 to 14, in cases 1 to 4, the degree of polymerization of the anticorrosive agent was unified to 16, and the difference in the anticorrosive effect due to neutralization with alkali metal was investigated. There is no significant difference between them.

5 to 8 investigated the anticorrosive effects of various low-molecular-weight polyacrylic acids with different degrees of polymerization (n), and among them, 16.7 was overwhelmingly superior to the conventional examples of 15 to 18 or the cases without additives. It is judged that the amount of hydrogen gas generated is small and the degree of polymerization (n) is preferably 5 to 60. Furthermore, in the case of alkali metal salts, it has been shown that they are effective when the degree of polymerization (n) is 5 to 50.
This becomes clear when comparing the 140 group and the t/G1s~180 group.

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
Electrolyte solution saturated with zinc oxide in a wt% aqueous solution (when adding an anticorrosive agent, add 11,000 pp of the anticorrosive agent shown in Table 2)
This is a zinc negative electrode in which a dissolved electrolytic solution is gelled with carboxymethyl cellulose, and 60 to 160 mesh powder of zinc hydride or zinc hydrate alloy is dispersed in this gel. 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, and 7 is nickel plated. This is a positive electrode can made of stainless steel. A polypropylene gasket 8 is compressed between the positive electrode can 7 and the sealing plate 1 when the positive electrode can 7 is bent.

The prototype battery has a diameter of 11.6ff and a total height of 6.4H. After storage at 60°C for one month, changes in discharge performance and total battery height, and leakage were observed by visual inspection. Table 2 shows the number of batteries used. The discharge performance was expressed as the discharge duration when discharging at 510Ω at 20″C with a final voltage of 0.9μ.

Table 2 [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; In a battery that generates a large amount of gas, the total height of the battery tends to increase due to an increase in the internal pressure of the battery. Therefore, the corrosion resistance of the negative electrode zinc can be evaluated by the increase or decrease in the total height of the battery during the storage period. 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 of all, Zinc alloys 1 to 7 have extremely good corrosion resistance as negative electrode active materials, and if the corrosion rate is 1.6 or higher, they are promising for use as negative electrodes in practical batteries without the aid of anticorrosive agents. (Zinc alloy containing Pb, In, and AI) was constructed with an extremely low corrosion rate of 0.05%, and the effects of the anticorrosive agent were compared. 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 the conventional anticorrosive agent is added or not added. It has been shown that by using a corrosion-resistant zinc alloy and the anticorrosive agent of the present invention in combination, sufficient corrosion resistance of the negative electrode can be ensured with a freezing rate of 0.05'1 or more, and a zinc-alkaline battery with an extremely low freezing rate can be constructed. ing. In addition, &8~14 are currently being used as popular materials for 3
The effect of the anticorrosive agent of the present invention was investigated by reducing the freezing rate of a zinc alloy (zinc alloy containing Pb and In), which has been put into practical use with a freezing rate of 0.29 J, to 0.29J. In this case as well, there is a clear difference in battery performance between Examples &8 to 11 and the conventional examples of Black 12 to 14 or cases without additives. 0.2%
This shows that it is possible to construct a zinc-alkaline battery with a low corrosion rate that has sufficient negative wind corrosion resistance and excellent practical performance with the above concentration ratio. Furthermore, &15~2o is sufficient even if the present invention is applied to reduce the filtration rate to 3% when pure zinc powder, which normally requires a filtration rate of about 7 to 10%, is used as the negative electrode active material. This shows that it is possible to construct a practical battery. In addition, A21 to A26 are cases in which the effects of the present invention were confirmed to be sure when a zinc alloy with a corrosion rate of 1, 5 to 3, which can ensure almost the corrosion resistance of the negative electrode without the aid of anticorrosive agents, was used for the negative electrode. In the case of examples of JJ, A21-23 and A27-29, the properties are further improved compared to the conventional examples of A24-26 and A30-32 or cases without additives, and a high degree of corrosion resistance is ensured. This indicates that the quality has been stabilized due to the corrosion resistance. The effect of the present invention was investigated with a conversion rate of 0.2%.
0 as in Example 1 with zinc alloy containing Pb and In.
．． This shows that it is possible to achieve a conversion rate of 2.

& 35 to 44 are zinc alloys that are expected to have corrosion resistance almost equivalent to zinc alloys with improved corrosion resistance containing Pb, In, and Al, and have a freezing rate of 0.05.
%, and all examples (black 35, 37, 39, 41.43) showed that zinc alloys containing Pb, In, and Al were used even when the reduction rate was as low as 0.05%. Similar to Examples A1 to A4, excellent battery performance was exhibited. All of the above cases are the results of examining the effects of the present invention by dissolving an anticorrosive agent in the electrolytic solution.
45, 46, and 47 show examples of the present invention other than the method of adding an anticorrosive agent to the electrolytic solution. Both of &46 and 47, in which the material was impregnated with an anticorrosive agent, had almost the same effect as when the anticorrosive agent was dissolved in the electrolytic solution. In all of these cases, the anticorrosive agent gradually dissolves into the electrolyte after the battery is constructed, exerting its anticorrosive effect. In particular, when the separator or liquid retaining material is impregnated with the anticorrosive agent, the anticorrosion agent gradually dissolves into the electrolyte after the battery is constructed. Since penetration becomes faster, battery removal becomes easier and productivity is increased.

Effects of the Invention The present invention has made it possible to significantly reduce the freezing 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,
6...Silver oxide positive electrode. Name of agent: Patent attorney Toshio Nakao and 1 other person2-
-One zinc lithium---t) Mareta 5-m-Silver oxide bipolar Si

Claims (7)

[Claims] (1) Zinc using at least one member selected from the group of low-molecular polyacrylic acid, -[CH_2CH(COOH)]-_n, and salts obtained by neutralizing this with an alkali metal as a corrosion preventive agent for the negative electrode active material. alkaline battery. (2) The zinc-alkaline battery according to claim 1, wherein the degree of polymerization (n) of the anticorrosive agent is 5 to 50. (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%.