JPS6177268A - Zinc alkaline battery - Google Patents

Abstract

PURPOSE:To obtain a low amalgamated zinc negative electrode having good discharge performance and high corrosion resistance by alloying zinc with a specified amount of calcium and adding indium to the zinc alloy. CONSTITUTION:Zinc alloy containing 0.05-0.5wt% indium and 0.005-0.15wt% calcium is used as a negative electrode of zinc alkaline battery. Calcium contained in the zinc alloy is discharged with zinc and increases discharge utilization factor of zinc. Since indium which has large affinity with zinc exits on the surface of the zinc alloy, diffusion of mercury which is added to the zinc alloy for amalgamation to the interior of the zinc alloy and the interior of crystals of the zinc alloy is retarded. Regardless of use of a small amount of mercury, mercury concentration on the surface or in the grain boundary of the zinc alloy is kept high and corrosion resistance is increased.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a zinc-alkaline battery using zinc as a negative electrode active material, an alkaline aqueous solution as an electrolyte, and manganese dioxide, silver oxide, mercury oxide, oxygen, etc. as a positive electrode active material. It is about improvement.

A common problem with prior art zinc-alkaline batteries is corrosion of the zinc negative electrode by the electrolyte during storage.

Conventionally, it has been adopted as an industrial method to increase the hydrogen overvoltage using zinc hydrate powder, which is made by adding about 5 to 10% by weight of mercury to zinc, and to suppress corrosion to a level that poses no practical problems. . However, in recent years, in order to reduce pollution, there has been an increasing social need to reduce the amount of mercury contained in batteries, and research on species I has been conducted. For example, 51
),gallium.

It has been proposed to improve corrosion resistance and reduce the hydration rate by using alloy powders containing indium and other additives. Although this is effective in suppressing corrosion, it has the opposite effect of deteriorating strong discharge performance by reducing the hydration rate. In these proposals, the cause of the deterioration of strong discharge performance when considering the bushing rate is unclear, but the discharge product or the active zinc surface is covered, and the surface of hydroxide ions necessary for the discharge reaction is This is thought to be because the extent to which the supply of mercury is inhibited is greater than when the mercury content is high, and the establishment of a low hydration rate zinc negative electrode that has both edibility and strong discharge performance is considered an important future issue.

Furthermore, with the aim of improving manganese dry batteries, there has been a proposal that the use of zinc or a zinc alloy in which indium is added to a zinc alloy for the negative electrode is highly effective in preventing corrosion (Japanese Patent Publication No. 33-3204).

Among the above proposals, in addition to indium, the elements in the zinc alloy include Fe, Cd, Cr, Pb, Ca, 1
-1g.

The description includes cases in which Bi, Sb, AI, Ag, hh, Si, Ni, Mn, etc. are included as impurities or additives, or indium and lead are used together as additive elements. 91 does not indicate at all whether the miscellaneous elements listed in L are included as impurities or added as effective elements, and it is not even clear whether these elements are effective for corrosion prevention. And what about the appropriate addition amount of indium?

There is no description of anything other than the ship's equipment. It remains a challenge for the future to study the effects of the combination of these elements in zinc-alkaline batteries and to find an effective alloy composition.

Problems to be Solved by the Invention As described above, there is a need for a zinc negative electrode for alkali batteries that has a low hydration rate, corrosion resistance, and strong discharge performance.

The present invention provides corrosion resistance 11:, discharge 11. The purpose of the present invention is to provide a zinc-alkaline battery that reduces the hydration rate without deteriorating the performance, has low pollution, and has excellent discharge performance, storage performance, Ii, and I leakage properties.

Means for Solving the Problems The present invention uses an aqueous alkali solution containing caustic glue, caustic soda, etc. as the main ingredients for the electrolytic i11, zinc as the negative electrode active material, and manganese dioxide, silver oxide, and oxide as the positive electrode active material. The negative electrode of a sub-I1) alkaline battery using mercury, oxygen, etc. contains >0.01-0.5% by weight of indium (In), calcium (Ca
) is characterized by using a zinc alloy containing 0.005 to 0.15% by weight.

Effect of the present invention First, the discharge reaction product covers the active zinc surface, impairs the lt supply of hydroxide ions, and the discharge reaction at a large current tends not to proceed smoothly. By adding an appropriate amount of Ca to the alloy, we solved the problems that occur when used in zinc alloys, and by adding In, which has a great effect on the anti-corrosion properties of zinc alloys. Through the synergistic effect with the above, we have realized a zinc negative electrode with a low water conversion rate that combines discharge performance and corrosion resistance. Although the mechanism of action regarding the effect of Ca addition has not been fully elucidated, as shown in the examples below,
It is effective within an appropriate amount of addition, and is effective for negative electrode "Tlj
k:) is discharged to both Ca and zinc contained in the alloy, and the discharge product promotes the dissolution of the zinc discharge product into the electrolytic solution or dissolves the undissolved discharge product. By densifying the zinc layer and slowing down the passivation effect on the zinc surface, the active surface of 'IE j'f) is supplied with abundant hydroxide ions and the zinc is depleted. Inherited from Zazu Mi and got 1v! This is considered to be due to the increase in the discharge utilization rate of IIi).

Among all elements, In is known as the most effective additive element for corrosion prevention, and has the effect of increasing the hydrogen overvoltage of zinc alloys.
/l! The surface of the t1) alloy has an affinity for mercury (
Due to the presence of mercury 11, the mercury added for hydration of the zinc alloy is fixed on the surface and grains W of the zinc alloy, and its diffusion inside the zinc alloy and within the crystal grains is suppressed. Therefore, by adding a small amount of mercury, the surface and
) <It is thought that maintaining a high silver concentration can have a large anticorrosion effect.

In the present invention, the above-mentioned effect of adding Ca not only improves the discharge performance, but depending on the amount added,
It has been recognized that Ca is effective in increasing the anti-corrosion effect of t), and when the zinc negative electrode is corroded by the electrolyte during the storage period of the battery, Ca takes precedence over zinc because it is a more base metal. It is presumed that the zinc alloy is oxidized and forms an acid film that inactivates the active sites on the surface of the zinc alloy, thereby inhibiting corrosion.

However, if it is present in too large a quantity, oxidation of Ca will proceed more than necessary, resulting in an increase in hydrogen gas generation, which will affect the discharge performance! : In order to obtain a zinc alloy with corrosion resistance, it is necessary to set appropriate amounts of both of the above elements.

Examples Various sub-6F) alloys were prepared by adding the elements shown in the table below to a zinc ingot with a purity of 99.997% or more, melted at about 500°C, and powdered by spraying with compressed air. ~+5
The particles were sieved to a particle size range of 0 mesh. Next, the above-mentioned powder was put into a 10% by weight aqueous solution of caustic No. 1, and a predetermined amount of mercury was added dropwise to the solution while stirring to hydrate it. Thereafter, it was washed with water, replaced with acetone, and dried to prepare a hydrated 11) alloy powder.

Furthermore, zinc hydrate alloy powders or zinc hydrate powders other than the examples of the present invention were also prepared in the same manner as comparative examples.

Using these hydrated powders, the cylindrical alkaline manganese battery shown in the figure was manufactured. In the figure, 1 is a positive electrode case made of iron coated with nickel metal. Inside is a positive electrode 2 made of a mixture of manganese dioxide and graphite and pressure molded, a separator 3 made of polypropylene nonwoven fabric, a bottom plate 4 made of cellulose,
Norboxymethyl cellulose is nylated or fi
The negative electrode 5 is housed in a square shape, each having a zinc hydrate alloy dispersed in a dilute aqueous electrolyte. 6 is a polypropylene sealing plate with the opening 11 of case 1 made 11 [1].
An h-pole collector 7 made of brass is fixed in the center. 8 is a negative terminal plate, 9 is a positive terminal plate, 10. II is an insulating ring,
12 is a heat-shrinkable resin tube; 13 is a metal tube (canned).

The prototype battery was an AA-sized alkaline manganese battery = 7-, the total amount of zinc hydrate alloy powder used for the negative electrode was unified to 2.80 g, and the amount of mercury added (consolidation rate) was changed to the zinc alloy powder. On the other hand,
The content was 3% by weight.

After storing the prototype battery at 60°C for one month, its continuous discharge performance at 10Ω, leakage resistance, and degree of expansion were evaluated at 20°C. The following table shows the test results for the sub-t1) alloy used in the negative electrode.

= 10 - seen in this table. Among the conventional examples, I
When only n is added (b to ``), gas generation is significantly suppressed compared to case (a) with no addition, but there is little expansion or leakage of the battery, but the strong load of 10Ω The duration of discharge is inferior to the performance of the product of the present invention, as described below.

Furthermore, the main purpose of smoothing the discharge reaction of the negative electrode is to
When only a is added (g, h), the corrosion protection is insufficient and the battery often expands and leaks, and the discharge performance also deteriorates significantly due to self-depletion during storage and discharge reaction due to built-in gas 1: ■ damage. are doing. As described in -1-, the conventional method (a -
h) With a water conversion rate as low as 3% by weight, a zinc negative electrode having both corrosion resistance and discharge performance cannot be obtained. On the other hand, In and C
Discharge performance among cases (1 to q) when a is added at the same time.

Good leakage resistance and little battery expansion (improved over conventional examples with In content of 0.01 to 0.5% by weight)
In the case of a sub-6F) alloy with Ca content of 0.005-0.15% by weight, F, k, I, o, p), it is inferior to or not much different from Add-11, and is suitable as in 2 series. A remarkable effect is observed within the range of the content of the added element.

As in Jul 2, the present invention complements the shortcomings of methods 1) to ``g'' and ``h'', and determines the content of added elements that can effectively obtain a synergistic effect, thereby achieving low pollution. This is a zinc-alkaline battery with excellent practical performance.

In addition, in the examples, a battery using a zinc hydrate negative electrode was explained, but the permissible amount of hydrogen gas generated is Since the amount of water is relatively large, when the present invention is applied to such a case, it is possible to reduce the water content even further, and in some cases, it may be possible to carry out the process with anhydrous state.

Effects of the Invention According to the present invention, the hydration rate of negative electrode zinc can be reduced and a low-pollution zinc-alkaline battery can be obtained.

[Brief explanation of drawings]

The figure is a partially sectional side view of an alkaline manganese battery used in an example of the present invention. 2... Positive electrode, 3... Separator, 5...
...Zinc negative electrode.

Claims (1)

[Claims] 0.01-0.5% by weight of indium, 0% of calcium
．． A zinc alkaline battery using a zinc alloy containing 0.005 to 0.15% by weight as a negative electrode active material.