JPS59205155A - Alkaline battery - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention uses VrC zinc as a negative electrode active material, manganese dioxide as a positive electrode active material, various depolarizers such as silver oxide, oxygen, mercury oxide, and nickel hydroxide, and an alkaline electrolyte as an electrolyte. The present invention relates to improvements in various alkaline batteries each using an aqueous solution.

A common problem of the conventional alkaline batteries described in [1] and [2] is to effectively suppress self-depletion due to corrosion of negative electrode zinc during storage and generation of hydrogen gas.

Therefore, conventionally powdered zinc is hydrated and pressure molded or dispersed in a gel to form a so-called gel negative electrode, and at least the surface of the negative electrode aggregate that comes into contact with this negative electrode is frozen. It is formed from metals that are easy to use and are electrochemically stable and inexpensive, such as copper, tin, and brass, and when it freezes, it increases the hydrogen overvoltage of the zinc itself, and it also diffuses from the zinc and migrates to the surface of the current collector. A commonly used method is to prevent corrosion by hydrating the current collector and increasing the hydrogen overcurrent capacity on the current collecting surface.

In this case, due to the potential difference between the zinc and the current collecting surface, a local cell is formed in which the zinc acts as an anode and the current collecting surface acts as a cathode, and a reaction occurs that generates hydrogen gas from the zinc melting "and the current collecting field". Or, when the mercury from the lead stops diffuses into the current collecting surface and the current collecting surface becomes frozen, the hydrogen overvoltage increases and the hydrogen generation reaction is suppressed, causing the zinc dissolution reaction corresponding to f'L. However, if zinc corrosion is inevitably suppressed, zinc corrosion is effectively suppressed to a satisfactory state, and this has the effect of ensuring storability as a practical battery and suppressing the acceleration of battery expansion and leakage. It recognized.

However, as a drawback of the above method, when compared to zinc punching,
(It is necessary to hydrate with about 6 to 12% mercury in terms of quantity ratio, and if the amount of mercury is insufficient, the hydrogen peroxide pressure in the local battery cannot be sufficiently increased, inhibiting the corrosion reaction. This means that a large amount of mercury must be used (/C) because it causes deterioration of storage performance, liquid leakage, and battery expansion. This is a social need due to pollution and is a factor that cannot be ignored in terms of cost reduction. Therefore, alloying of zinc and investigation of additives have been conducted as a means to reduce the amount of mercury in alkaline batteries. However, the current situation is that there is still no method that can be expected to have a significant effect.

purpose of invention The goal is to reduce pollution and reduce costs.

Composition of the Invention The present invention (・'1. Zinc as the negative electrode active material. An alkaline aqueous solution is used as the electrolyte, and at least the surface of the negative electrode current collector is electrochemically higher in quality than zinc, such as copper, tin, or surface edges. In various alkaline batteries made of metals that are easily amalgamated, tMj is characterized by the presence of cadmium on the surface of the negative electrode current collector in contact with the negative electrode active material.Cadmium has a large hydrogen overvoltage and has a low solubility in mercury. Cadmium has an extremely large property of about 4.9%, compared to about 2.2% of zinc, about 0.6% of tin, and 0.003% of copper. In addition, the corrosion reaction of zinc negative electrodes is dominated by a local battery reaction in which zinc dissolves as an anode and the surface of the current collector acts as a cathode, generating hydrogen gas. Recognizing that increasing the mercury concentration on the surface of the current collector to reduce hydrogen overvoltage is the most important issue in preventing corrosion of zinc, we decided to attach cadmium, which can increase the mercury concentration on the surface of the current collector. It is something that

It has been found that this method can sufficiently suppress corrosion even when the mercury concentration in zinc is extremely low.

The amount of mercury that diffuses and transfers from zinc hydrate to the current collector surface increases as the mercury content in the zinc hydrate increases.
Furthermore, what is important in understanding the mechanism of action of the present invention is that
The higher the compatibility with mercury on the surface of the current collector, that is, the greater the solubility, the higher the mercury migration 1i5 to the surface of the current collector, that is, the higher the concentration of mercury. Conventionally, tin, copper, and brass, which have been used as surface materials for current collectors, have poor compatibility with mercury compared to zinc, so they can only be applied to the surface of current collectors at concentrations lower than the mercury concentration in zinc. Unless the water concentration in the negative electrode zinc is at a high concentration of 5 to 12 wt to maintain the mercury concentration, water Qk a is sufficient to increase the hydrogen overvoltage on the surface of the body.
I can't do it. On the other hand, by making clear domicum, which has extremely high affinity with mercury, exist on the surface of the current collector, it becomes possible to contain mercury in cadmium at a much higher concentration than that in zinc. Even when the degree of mercury in zinc is low, the mercury concentration on the surface of the current collector can be increased, and the local battery and action can be effectively made negative by increasing the hydrogen concentration by -1.

The above explanation has been made with a battery configuration method in which all mercury is transferred from frozen zinc to the current collector surface to suppress local effects, but in the case of the present invention, the battery configuration is changed as described below. It is also effective to apply this method to a battery construction method in which the surface of the current collector is hydrated to a high concentration in advance, and 111j lead, which is anhydrous or has a low freezing rate, is used as the negative electrode.

In other words, in the conventional method in which the current collector surface is formed only with metals such as copper, surface edge, and tin that are compatible with mercury or are smaller than lead, even if the current collector surface is hydrated to a high concentration in advance, , After battery construction 9, mercury gradually migrates to the zinc oxide, and the mercury concentration on the surface of the current collector decreases, so the local battery action becomes active.
This means that the corrosion reaction of zinc cannot be suppressed. In contrast, in the present invention, the relationship between mercury compatibility between cadmium on the surface of the current collector and zinc is completely opposite. Even after formation, the mercury concentration in the zinc is extremely low, and the corrosive reaction of zinc due to local action can be effectively suppressed in the sintered state.

As mentioned above, the present invention can maintain the mercury concentration on the surface of the current collector in a high state even when the mercury concentration in zinc is low, effectively suppressing the corrosion reaction of 4 ml lead, and reducing the mercury concentration on the surface of the current collector. Niba,
Even at high concentrations, the absolute sum of mercury is extremely low (ft:J), so the amount of mercury used can be greatly reduced.

DESCRIPTION OF EXAMPLES In order to specifically demonstrate the effects of the present invention, an experiment using a button-type alkaline manganese battery will be described below. The figure is a cross-sectional view of the battery used in the experiment. In the figure, 1 is a sealing plate, which has a core material of Φ÷iron, an outer surface 1' of which is nickel, and an inner surface 1" of which is a clad plate with an edge.
The composition is a zinc negative electrode containing frozen powder made by freezing 50 to 100 meshes of zinc powder at a ratio of 4Φ as described below. f: A gel electrolyte solution is used which is saturated and further has carboxymethylcellulose dispersed therein as a gelling agent. 3 is a liquid retaining material made of cellulose, 4 is a microporous 1η- polypropylene separator, 6 is a positive electrode made by adding and mixing manganese dioxide with artificial graphite, 6 is a positive electrode ring made of stainless steel, and 7 is made of iron. A positive electrode case consisting of a nickel 7' clad plate as the core material, both on the outer and inner surfaces.
8 is a polypropylene gasket, and the positive electrode case 7
Sealing is accomplished by bending the opening. In addition to the negative electrode 2, a liquid retaining material 3, a separator 4, and a positive electrode 5 are impregnated with the electrolytic solution, and the liquid composition is the same as that of the electrolytic solution in the negative electrode 2. Here, since the part that acts as the negative electrode current collecting surface is the inner surface 1'' of the sealing plate 1, the effects of the present invention will be examined by varying the conditions of the lower and inner surfaces of the sealing plate and the hydration rate of zinc. Table 1 shows the contents of the prototype.

Table 1 below: Use zinc powder with a particle size of 50 to 100 meso/yu and a purity of 99.9 or higher. Place the zinc powder in a potash solution with a concentration of about 10 wt and stir. While doing so, a predetermined amount of mercury was added, and the mixture was washed with water and dried to form ice. The shape of the prototype button battery is 1t1, 11.6mm in diameter, and 3 in total height.
, unified to 0 axilla. For each of these prototype batteries (a-q), the discharge performance and 'I+i,/l! Table 2 shows the results of investigating the total height change and occurrence of leakage.

As shown in Table 2 below, when untreated brass is used for the inner surface of the sealing plate (a-e), the battery expands when the hydration rate of zinc is 3 wt% or less (c, d, e). Both the leakage and leakage were significant, indicating that the pressure inside the battery had increased due to hydrogen gas generated during storage.

To completely suppress the generation of hydrogen gas, 10 wt of hydration a is required. Although these problems can be solved to the extent that there is no major problem in practical use even if the diameter is about 5φ, there is still a shortcoming in terms of reliability. Furthermore, the deterioration of discharge performance after storage is greater as more hydrogen gas is generated, and this is thought to be due to poor chemical and physical contact due to gas pressure and consumption of zinc. In addition, as an application example of the present invention, a method of coating cadmium on the surface of brass (■ ~
In l), the problem after storage is that the hydration rate of salivary lead is 6wt.
%f1 completely eliminates the problem, and even with 1 to Swt ratios g and h, an effect equivalent to 5wt%b when not coated with cadmium is obtained. Further, even if cadmium is coated, if mercury is insufficient or not contained in zinc, B and H will have a poor effect in suppressing the generation of hydrogen gas, and storage performance will also deteriorate.

Next, after hydrating the inner surface of the sealing plate in advance, construct the battery.
However, the effects are different when the inner surface of the sealing plate is made of brass and when it is coated with cadmium, and the latter has extremely poor properties after storage.
There is no problem at all when n and o are more than Iwt, and there are few problems even when p and q are less than 0.5wt%.

These results demonstrate that the effects of the present invention described above are actually realized. +
I-It is something to do.

As described above, the present invention effectively suppresses corrosion of zinc negative electrode in alkaline electrolyte by using mercury.
This is extremely effective in reducing battery pollution and cost.

[Brief explanation of the drawing]

The figure is a sectional view of a button-shaped alkaline battery used in an experiment to demonstrate the effects of the present invention. 1 is the sealing plate, 1″ is the inner surface of the sealing plate that also serves as the negative electrode current collecting surface,
2 is 1''l (lead page electrode, 3 is liquid retaining material, 4 is separator, 5 is
is the positive electrode, 6 is the positive electrode ring, 7 (/i, i]-pole one step,
8 is a gasket.

Claims (1)

[Claims] Using zinc as the negative electrode active material and an alkaline aqueous solution as the electrolyte, at least the negative electrode active material of the negative electrode current collector is