JPH0119622B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to alkaline batteries, such as alkaline manganese batteries, silver oxide batteries, and air batteries, which use zinc as a negative electrode and an alkaline electrolyte. The object of the present invention is to provide a battery that can be used as a practical battery by reducing the amount of mercury compared to conventional alkaline batteries, suppressing gas generation from the negative electrode, and at the same time preventing deterioration of heavy load discharge characteristics. . In conventional alkaline batteries, zinc powder is usually used to increase the reaction area of the negative electrode, and amalgamation is performed to increase the hydrogen overvoltage and prevent gas generation. However, since the surface area is large, 5 to 10 wt% of mercury is required relative to zinc.
For example, in large alkaline batteries such as JIS LR20, LR14, or LR6, the amount of zinc used in the negative electrode is large, so the amount of mercury is also inevitably large. For these reasons, various metals have been added to zinc in order to reduce the amount of mercury, prevent corrosion of zinc in alkaline electrolyte, suppress gas generation, and thereby prevent leakage of electrolyte. It is proposed to add For example, according to Japanese Patent Application Laid-open No. 53-103127, zinc is coated with an alloy of indium (In) and gallium (Ga), either alone or in a mixture with mercury, and in this case, indium or gallium is 2 to 10 wt% of mercury to zinc, and 2 to 10 wt% of mercury to zinc.
It is coated with a concentration of 14wt%. Other examples include tantalum (Ta), thallium (T), gallium (Ga), and indium (In).
JP-A-53-41733 also discloses that one or three of these and no mercury or a trace amount of mercury may be amalgamated in arbitrary proportions and coated on zinc powder. In this conventional example, the amount of mercury added is not specifically described. Furthermore, JP-A No. 47-35727 discloses that an intermetallic alloy or an interstitial alloy obtained by chemical or electrolytic co-reduction or electrolytic co-deposition method is used as a homogeneous solid-phase molten alloy at the melting point or at the melting point. A zinc alloy containing gallium (Ga), lead (Pb), and germanium (Ge) obtained by a well-known method to form a homogeneous solid-phase soluble alloy in a nearby area is injected with 10wt of mercury relative to zinc.
Alkaline batteries using % amalgamated negative electrodes have also been proposed. From the description of each of the above conventional examples, it is found that using mercury in the range of a minimum of 2wt% to a maximum of 14wt% relative to zinc is effective in suppressing gas generation that promotes electrolyte leakage and improving heavy-load discharge characteristics. Therefore, it can be understood that the amount added is appropriate. When using the load described in the conventional example above,
Although the effects of suppressing the amount of gas generated and increasing heavy load discharge characteristics can be sufficiently obtained, it is desirable to reduce the amount of mercury used as much as possible from the viewpoint of environmental pollution. Currently, used alkaline batteries are buried in the soil and sprayed with artificial seawater to measure the amount of mercury eluted.
As a result of measurement in accordance with the 0102 factory wastewater test, the elution amount after one year was 0.3 μg/, and it is necessary to obtain an alkaline battery that uses a smaller amount of mercury and does not deteriorate the battery discharge performance. As a result of various studies, the present inventors found that gallium,
The amount of mercury is 0.05wt relative to zinc in the alloy powder of two or more metals of indium and thallium and zinc.
It has been found that by using a negative electrode containing mercury in an amount of 1.8 wt % or more in an alkaline battery, the heavy load discharge characteristics are not impaired and an alkaline battery without mercury elution can be obtained. Embodiments of the present invention will be described below with reference to the drawings. Example 1 1 is a metal container in which a positive electrode mixture 2 containing manganese dioxide and scaly graphite is filled under pressure. 3 is a separator made of a mixture of pulp and synthetic fibers, and inside is a negative electrode 4 containing mercury in zinc powder having the alloy composition shown in Table 1 below, and an alkaline electrolyte saturated with zinc oxide containing polyacrylic acid. It is filled with an electrolyte made into a gel with soda. 5 is an insulating gasket made of synthetic rubber or polyethylene. A brass current collector rod 7 welded to the negative electrode terminal plate 6 is inserted into the center of the negative electrode 4. An insulating tube 8 covers the outer circumferential edge of the positive terminal plate 9, the negative electrode terminal plate 6, and the outer circumferential edge of the metal container, and the upper and lower open ends of the metal exterior can are bent inward to form an alkaline battery with a sealed opening. The zinc alloy powder in the above examples was obtained as follows. In this example, predetermined amounts of three metals, gallium, indium, and thallium, were added to molten zinc, stirred and mixed to form an alloy, and then zinc powder was prepared. This alloy powder was amalgamated by pouring metallic mercury into a slightly alkaline aqueous solution while stirring, then washed with water, and dried under reduced pressure at approximately 60°C to prepare the powder. The alloy composition is shown in Table 1, and the heavy load discharge performance and mercury elution amount were measured using the negative electrode of the JIS name LR6 type alkaline battery described in the above example.
Shown in the table.

[Table] In Table 1, the zinc utilization rate is the utilization rate of the zinc negative electrode determined from the discharge duration until the final voltage is 0.9V when constant current discharges are performed at 250 mA and 500 mA. The amount of mercury eluted was determined by chemically analyzing the mercury eluted into the soil one year after burying a battery with a hole in a metal container in the soil and spraying artificial seawater. In the alloy compositions of samples No. 1 to 3 in this example, the zinc utilization rate is high in all cases.
This value was higher than that of a conventional product containing 6.4 wt% of mercury in amalgam form. The reason for this is that the three metals gallium, indium, and thallium prevent corrosion of zinc, and the amount of mercury relative to zinc is 0.05wt% or more and 1.8wt%.
This is considered to be because self-discharge of zinc in the electrolytic solution is prevented even if the amount is below. In addition, in order to further clarify the effects of the present invention,
The amount of gas generated was measured to evaluate the corrosivity of negative electrode zinc. This test involved zinc oxide saturated
Each sample No. 1 to 7 in 3.5 ml of 35 wt% caustic potash solution
Weigh and soak 5.00g of zinc alloy powder up to 45
The hydrogen gas generated after being left at ℃ for 72 hours was captured and the amount of gas generated (ml/g/day) was determined. The result is the second
Each is shown in the table.

[Table] As can be seen from this table, in the range of 0.05 to 1.80 wt% mercury, the gas generation amount is 0.002 to 0.006 ml/g/day, and the comparative sample No. 4, which does not contain mercury Since the amount of mercury of 0.04wt% in Sample No. 5 and Sample No. 5 results in gas generation of 0.045ml/g/day and 0.009ml/g/day, respectively, the three metals of the present invention are alloyed with zinc. It can be seen that it has a preservative effect. In addition, the amount of mercury is required to be 0.05wt% or more compared to samples No. 5 and No. 6 of the comparative example, and from the relationship with the amount of mercury elution shown in Table 1, it is 1.8wt%.
The following are desirable. In each of the examples described below, gallium is added to zinc.
Zinc powder was obtained by melting two metals, indium and thallium, and amalgamated with mercury in the same manner as in Example 1. Further, the zinc utilization rate and the mercury elution amount were measured using an LR6 type alkaline battery having the same structure as described in Example 1, and the same test method as in Example 1 was used for the gas generation amount. Example 2 In this example, a zinc alloy powder of zinc-gallium-thallium was used as the negative electrode. The alloy composition is shown in Table 3, and the amount of gas generated is shown in Table 4.

【table】

[Table] Example 3 In this example, a zinc alloy powder of zinc-indium-thallium was used as the negative electrode. The alloy composition is shown in Table 5, and the amount of gas generated is shown in Table 6.

【table】

[Table] Example 4 In this example, a zinc alloy powder of zinc-gallium-indium was used as the negative electrode. The alloy composition is shown in Table 7, and the amount of gas generated is shown in Table 8.

【table】

[Table] Comparing the above examples, the one in which mercury amalgam is made of an alloy of zinc and three metals, gallium, indium, and thallium, has an excellent zinc utilization rate and gas generation amount. Even when two types of thallium are selected and made into an alloy, the zinc utilization rate is at least 92 at 250mA discharge.
%, 79% at 500mA discharge, which is slightly inferior to the conventional product amalgamated with 6.4wt% mercury, but at this level there is no problem in using it as a practical battery. In the present invention, the metals added to zinc as an alloy are limited to three types, gallium, indium, and thallium, because these three types of metals have a particularly high corrosion-preventing effect among metals that exhibit a corrosion-preventing effect. Further, if only one of these metals is used, the zinc utilization rate and gas generation amount will be high in any case, and the effects of the present invention cannot be expected. Furthermore, in the present invention, the amount of mercury is reduced to 0.05wt% or more.
The reason for limiting the amount to 1.8wt% or less is that as shown in the zinc utilization rate, 0.05wt% or more is necessary from the viewpoint of heavy load discharge characteristics, but considering the impact on the natural environment due to mercury elution, 1.8wt% or less is better. . In the case of the battery of the present invention, gallium, indium, and thallium remain in an amalgamated form with mercury, and therefore are considered to be difficult to elute. As described above, the present invention can provide an alkaline battery with reduced mercury content without impairing heavy load discharge characteristics.

[Brief explanation of drawings]

The drawing is a longitudinal sectional view of an alkaline battery in an embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Metal container, 2... Positive electrode mixture, 3... Separator, 4... Negative electrode, 6... Negative terminal plate, 7... Current collector rod.

Claims (1)

[Claims] 1 2 of gallium, indium, and thallium
What is claimed is: 1. An alkaline battery comprising: a negative electrode comprising a zinc alloy powder containing at least 0.05 wt% and 1.8 wt% of mercury based on zinc;