JPS63239770A - Zinc alkaline cell - Google Patents

Abstract

PURPOSE:To reduce the amount of mercury which is used for gelatinization of a negative electrode by using alkylbenzenesulfonate and at least one selected from a salt group which are made by neutralizing the alkylbenzenesulfonate with an alkaline metal as the anticorrosive of a negative electrode active material. CONSTITUTION:As an anticorrosive to suppress the corrosion of a negative electrode, alkylbenzenesulfonate and at least one selected from a salt group which are made by neutralizing the alkylbenzenesulfonate with an alkaline metal are used. When the anticorrosive is absorbed to the surface of the negative electrode and formed into a membrane, hydroxide ions to be a cause of the anode reaction are disturbed from approaching the zinc negative electrode, while water molecules necessary for the cathode reaction can not exist near the surface of the zinc negative electrode, and the corrosion of the zinc is suppressed. The gelatinization rate of the negative electrode can be reduced accordingly.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is directed to a zinc alkali solution using zinc as a negative electrode active material, an alkaline aqueous solution as an electrolyte, and manganese dioxide, silver oxide mercury oxide, oxygen, nickel hydroxide, etc. as a positive electrode active material. This provides an effective means for reducing the amount of mercury used in zinc negative electrodes for batteries.

BACKGROUND OF THE INVENTION Conventionally, in order to suppress corrosion of the electrolyte of this type of zinc negative electrode, a method of adding about 7 to IO weight % of mercury to zinc has been used industrially. However, in recent years, there has been an increasing social need to reduce mercury content in order to reduce pollution.
Various corrosion-resistant zinc alloys have been developed or proposed in order to ensure sufficient corrosion resistance with the use of a small amount of mercury. For example, indium, lead, gallium, aluminum,
Corrosion-resistant zinc alloy powder with the addition of indium and lead is considered to be effective, and zinc alloy with the addition of indium and lead has already been put into practical use.In order to further improve corrosion resistance, in addition to indium and lead, aluminum can be added as needed. Furthermore, zinc alloys to which gallium is added are being considered as a representative 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, and in the case of zinc alloys containing indium and lead, the hydration rate is 3% by weight. (hereinafter referred to as %) This is further improved in a zinc alloy in which in addition to the above-mentioned indium, aluminum, and lead, aluminum and gallium are added as necessary, the oxidation rate is 1.5%.
Corrosion resistance equivalent to a hydration rate of 7 to 10% in the case of pure zinc can be obtained. As seen in the above example, the use of a corrosion-resistant zinc alloy is an effective method for reducing the hydration rate, but another effective method is to add an anticorrosion agent, which reduces mercury in the battery. The combined use of corrosion-resistant zinc alloys and anticorrosive agents is considered essential as a technique to reduce the content to the absolute minimum.

Conventionally, in order to prevent corrosion of a zinc negative electrode in an alkaline aqueous electrolyte, glycols such as ethylene glycol, mercaptocarboxylic acid, aminonaphthalene sulfonic acid, azonaphthalenes, carbazole, cyanohydrin, and thiazoles such as 2-meltocaptobenzothiazole have been used. Application of various anticorrosive agents, including benzotriazole derivatives and derivatives thereof, has been proposed. The general application method is to add a small amount of these anticorrosive agents to the electrolyte.

However, no significant anticorrosion effect was observed with any of the anticorrosive agents.
Currently, there is no effective means to reduce the rate of ice formation.

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, this 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 to do this, we will search for a new preservative that has a greater anticorrosion effect than the various anticorrosive agents previously proposed (i.e., is alkaline resistant and does not have a negative effect on discharge performance). The present invention is applied to batteries equipped with a negative electrode, and provides a low-pollution zinc-alkaline battery with a low mercury content without impairing the performance characteristics of a practical battery.

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,
Using oxygen, nickel oxyhydroxide, mercury oxide, etc.
One type of alkylbenzene sulfonate is used as an anticorrosive agent to suppress corrosion of the negative electrode of a so-called zinc-alkaline battery.

These anticorrosives can be applied by adding them into an electrolytic solution, impregnating them into 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 5 to 35 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 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 hydration rate of 0.2%; If a zinc alloy containing at least one of aluminum, strontium, calcium, magnesium, potassium, and nickel is used in combination with the zinc alloy, the corrosion resistance of the negative electrode can be ensured even at a freezing rate of 0.05%.

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 with a sulfonic acid group as a polar group at one end and a hydrophobic alkyl group at the opposite end, and dissolves or disperses when added to an electrolyte. It is thought that the polar groups are adsorbed on the surface of the zinc or zinc alloy of the negative electrode. The corrosion reaction of zinc in an alkaline electrolyte is shown by the following equation.

Anodic reaction Zn+40H-→Zn(OH)4+2e-Cathode reaction 2H20+2e--'-208-+H.

When the anticorrosive agent adsorbs to the surface of the negative electrode and forms a film, it prevents the hydroxide ions that cause the anode reaction from approaching the zinc negative electrode, and the water molecules necessary for the cathode reaction cannot exist near the surface of the zinc negative electrode. Zinc corrosion is suppressed. 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 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, zinc is adsorbed to the present invention and corrosion of zinc is suppressed. As described above, the anticorrosive agent used in the present invention is thought to have an anticorrosion effect because it covers the surface involved in the corrosion reaction of zinc. Zinc alloy or JP-A-6
0-175368, JP-A-61-77267, JP-A-61-181068, JP-A-61-203563, etc., which contain indium and lead, and further include 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 if the icing rate is reduced to about 0.2%. . However, when the above anticorrosives are used together, 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 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. Shitachi.

It is.

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 5me, and then freeze in the solution. 10g of zinc powder was added, and the amount of hydrogen gas generated over 20 days at a temperature of 45°C was measured. The freezing rate of frozen zinc powder is 1.0%, and the particle size is 3.
The number was 5 to 150 meshes. The measurement results obtained are shown in Table 1.

In Table 1, the group of Nnl-11 using the anticorrosive agent of the present invention is different from the group of NQ11 using the anticorrosive agent proposed conventionally.
The amount of hydrogen gas generated was smaller than that of the groups NQI to NQ14 and FF115 to which no anticorrosive agent was added (it can be seen that the corrosion inhibiting effect of the anticorrosive agent of the present invention is large. Among the groups NQI to NQ11,
In N11-43, the number of carbon atoms in the alkyl group of the anticorrosive agent was unified to 12, and the anticorrosive effect was investigated when the number of carbon atoms in the alkyl group of the anticorrosive agent was varied by neutralization with an alkali metal. As you can see by comparing Arashi 1 to 4 to 7, the alkyl group has 5 to 35 carbon atoms (Ki 1 and Fk5.Th6)
shows a hydrogen gas generation amount of 172 or less in the case of Arashi 15 without additives, which is particularly good. Other anticorrosive agents of the present invention also have anticorrosion effects in the same carbon number range.
This is clear from the results of the amount of hydrogen gas generated in No. 11.

(Example 2) Next, based on the results obtained in Example 1, a typical anticorrosive agent was selected, and its effect on reducing the corrosion rate of zinc or zinc alloy, which is a negative electrode active material, was evaluated using the buttons shown in Figure 1. A prototype silver oxide battery was manufactured and compared. In FIG. 1, reference numeral 1 denotes a sealing plate made of stainless steel, the inner surface of which is plated with steel. 2 is an electrolytic solution in which a 40% by weight aqueous solution of potassium hydroxide is saturated with zinc oxide (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. This is a zinc negative electrode in which 50 to 150 meshes of powder of zinc hydrate or zinc hydrate alloy are dispersed in this gel. 3 is cellulose-based liquid retaining material, 4
5 is a porous polypropylene separator, 5 is a positive electrode made of a mixture of silver oxide and graphite and pressure molded, 6 is a positive electrode ring made of nickel-plated iron, and 7 is a nickel-plated stainless steel positive electrode can. be. A polypropylene gasket 8 is compressed between the positive electrode can (7) and the sealing port (1) by bending the positive electrode can (7). The prototype battery has a diameter of 11.6 m and a total height of 5.4 m.

Table 2 shows the changes in discharge performance and total battery height of the prototype batteries after storage at 60° for one month, and the number of batteries in which leakage was observed by visual inspection. The discharge performance was expressed as the discharge connection time when discharging at 20° C. with a 510Ω load and a final voltage of 0.9V.

Table 2 Table 2 (#fE) Table 2 (one after another) In normal button batteries, after sealing the battery, the total battery height increases over time until the stress relationship between each battery component becomes stable. However, in batteries where a large amount of hydrogen gas is generated, as evidenced by the corrosion of the negative electrode zinc, there is a strong tendency for the total battery height to increase due to an increase in battery internal pressure. The corrosion resistance of zinc can be evaluated.Batteries with insufficient corrosion resistance will not only increase the total height of the battery, but also be prone to leakage due to increased battery internal pressure, and discharge performance will deteriorate due to consumption of negative electrode zinc due to corrosion and surface oxidation.

From this point of view, the prototype experiment results shown in Table 2 are evaluated as follows. First, l1hl~6 has extremely good corrosion resistance as a negative electrode active material, and if the corrosion rate is usually 1.5% or more, zinc alloy (Pb The effectiveness of the anticorrosive agent was compared by constructing a battery with an extremely low corrosion rate of 0.05% (zinc alloy containing , In, and AI). Cases 1 to 3 in which additives were added were significantly better than cases in stones 4 to 6 in which conventional anticorrosion agents were added or no additives were added, and the above corrosion-resistant zinc alloys and the present invention 0 by using anti-corrosion agent.
．． It is shown that sufficient corrosion resistance of the negative electrode can be ensured with a freezing rate of 0.05% or more, and that a zinc-alkaline battery with an extremely low freezing rate can be constructed. In addition, NQ7 to 12 are zinc alloys (Zinc alloys) that are currently in practical use as popular materials with a 3% filtration rate.
The effect of the anticorrosive agent of the present invention was investigated by reducing the viscosity of a zinc alloy containing Pb and In to 0.2%. In this case, the embodiment of ll & 17-9 is NQIO
A clear difference in battery performance can be seen between the conventional example of ~12 and the case without additives, and when the above zinc alloy and the anticorrosive agent of the present invention are used together, the corrosion resistance of the negative electrode is improved with a corrosion rate of 0.2% or more. This shows that it is possible to construct a zinc-alkaline battery with a low wood reduction rate that is sufficient and has excellent practical performance. Furthermore, in &13 to 18, when pure zinc powder, which normally requires a filtration rate of about 7 to IO%, is used as the negative electrode active material, it is sufficient to reduce the filtration rate to 3% by applying the present invention. This shows that it is possible to construct a practical battery. In addition, Arashi 19-26 showed that the effect of the present invention can be achieved when a zinc alloy with a corrosion rate of 1.5 to 3% is used for the negative electrode, which can ensure the corrosion resistance of the negative electrode without the aid of anticorrosive agents. It was confirmed that ff119.20 and N
In the case of the example of n23.24, the properties are further improved than the conventional example of Nh21, 22, and ff125.26 or the case of no additives, and the quality is stabilized by ensuring a high degree of corrosion resistance. It shows.

Nn29,30 is the result of investigating the effect of the present invention using a zinc alloy containing Pb, In, and Ga with a corrosion resistance of 0.2%, which has almost the same corrosion resistance as a zinc alloy containing Pb and In. In the case of the example, it is shown that a filtration rate of 0.2% can be achieved, similar to the examples of Arashi 7 to 9 with zinc alloys containing Pb and In.

Nn27-28 is expected to be a zinc alloy with almost the same corrosion resistance as a corrosion-resistant zinc alloy containing Pb, In, and AI, and has a corrosion rate of 0.05.
%, the effect of the present invention was investigated, and any of the examples (I
Vkt27.29.31.33.35) also shows excellent battery performance even at a low level of 0.05%, similar to the example of Nnl-3 in a zinc alloy containing Pb, In, and Al. . 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.
9.40.41 shows an embodiment of the present invention other than the method of adding an anticorrosive agent to the electrolytic solution. Almost the same effect was observed when the material was impregnated with an anticorrosive agent and 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 anticorrosion effect. In particular, when the separator or liquid retainer is impregnated with the anticorrosive agent, the anticorrosion agent gradually dissolves into the electrolyte after the battery is constructed. Penetration is rapid, which simplifies battery construction and has the effect of increasing productivity.

(Example 3) Next, as a typical anticorrosive agent, The relationship between the solution concentration and the amount of corrosion of zinc hydrate alloy powder was investigated.

Zinc hydrate alloy powder contains 0.05% each of Pb, In, and AI.
Using a mercury drop method in an alkaline solution on the ends of 35 to 150 meshes of zinc alloy containing zinc, we hydrated it at a filtration rate of 0.05%, weighed 10g of it, and added potassium hydroxide. The grains were immersed in an electrolytic solution containing a 40% by weight aqueous solution of zinc oxide and dissolved in an anticorrosion agent, and then heated at 45°C.
The sample was left to stand for O days, and the amount of hydrogen gas generated during that time was measured. The anticorrosive agent in the electrolytic solution was adjusted by mixing an electrolytic solution saturated with an anticorrosive agent and an electrolytic solution containing no anticorrosive agent in an appropriate ratio. The results are shown in FIG.

As seen in Fig. 2, a remarkable effect is seen above, and an almost constant effect is obtained above about 500 PPm up to the saturation concentration of about 1.900 PPn+. In addition to this anticorrosive agent, the anticorrosive agents used in steps 1 to 3 of Example 1 also had similar effects, and the appropriate concentration of the anticorrosive agent of the present invention is from about 1.0 OOPPo+ or more to less than the saturated concentration. It was found that it is preferable to

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 drawings]

Figure 1 is a partially sectional side view of a button-shaped silver oxide battery used in an example of the present invention, and Figure 2 shows the relationship between the amount of anticorrosion agent dissolved in the electrolyte and the amount of hydrogen gas generated. It is a diagram. 2...Zinc negative electrode, 4...Separator,
5...Silver oxide positive electrode. Name of agent: Patent attorney Toshio Nakao and one other person 2---i
Minoru Komae-1 Paleta

Claims (7)

[Claims] (1) A zinc-alkaline battery using at least one selected from the group consisting of alkylbenzene sulfonates and salts obtained by neutralizing these with alkali metals as a corrosion inhibitor for the negative electrode active material. (2) The zinc-alkaline battery according to claim 1, wherein the alkyl group of the anticorrosive agent has 5 to 35 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 patent 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% by weight. 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 consisting 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% by weight.