JPS6110860A - Alkaline zinc battery - Google Patents

Abstract

PURPOSE:To reduce the generation of hydrogen gas within an alkaline zinc storage battery to improve the characteristic of storage by using low amalgamated or unamalgamated zinc alloy powder which contains specific metallic elements and is specified with a amalgamation rate and a bulk specific gravity as active material for a negative pole. CONSTITUTION:In an alkaline battery, low amalgamated unamalgamated zinc alloy powder with a spraying state, which contains two or more kinds of metallic elements belonging to the groups of I b, IIb, IIIb, IVb, Vb, and has an amalgamation rate under 2wt% and a bulk specific gravity under 3.5g.cm<-3>, is used as active material for a negative pole. Preferrably, the containing rate for zinc oxide in the alloy powder is set to be under 0.2wt%. According to the alkaline battery, it is possible to restrain the generation of hydrogen gas within a battery in the same degree as a battery, in which zinc powder with a high amalgamation rate is used in the conventional manner. Further, it is possible to increase the volume of the active material in the same volume of the negative pole and improve the characteristic of rapid discharging in low temperatures.

Description

[Detailed Description of the Invention] 1. Technical Field of the Invention] The present invention relates to a zinc negative electrode that is used with a low or zero concentration rate in an alkaline electrolyte containing an alkali metal hydroxide as the main electrolyte. It is.

[Technical background of the invention] Zinc powder or zinc alloy powder, which is generally a negative electrode material for alkaline batteries, can be produced by various methods, but the most widely used method is 4N (purity 99.99%).
A zinc powder consisting of a group of irregularly shaped particles obtained by atomizing using the above-mentioned high-purity electrolytic zinc, with a particle size (minor diameter) of about 60flIIl to 350 μm,
It has a shape index of about 2.0 to 2.3 and a zinc oxide content of about 0.2% to 0.3% by weight.

[Issues with back-stain technology] This kind of zinc powder has a low hydrogen overvoltage in an alkaline electrolyte, and the chemical polarization when discharged in a battery where the amount of electrolyte is actually extremely limited is also compared. Due to the large size of the frozen zinc powder, it is common to use it with various degrees of freezing (amal(]amatiOn) depending on the type, structure, and purpose of use of the battery. The weight ratio is in the range of 5% to 25% by weight, but a ratio of about 1% to 12% by weight is particularly frequently used.

In addition, the zinc oxide content is 0.4% by weight to 0.9% by weight.
Many of them are about % by weight.

The presence of a large amount of mercury in the negative electrode is inevitably a design problem.
This is not preferable because it leads to a decrease in the amount of active material within the volume determined for the negative electrode to occupy within the battery, resulting in a decrease in battery capacity. In addition, as is well known, mercury is a pollution control substance, and reducing its usage has become a particularly strong social demand in recent years.

Research has been widely conducted to reduce the amount of mercury added in negative electrode zinc, and the main methods for improving this are zinc alloy composition, surface treatment of zinc particles, and corrosion inhibitors (formerly known as InL) in the alkaline electrolyte. ). Among these, one of the most basic methods is the addition of a third metal element that increases the hydrogen overvoltage by alloying with zinc and does not impede the discharge characteristics. Most of the proposed additive elements/υ
What is Group Ib, Group 1 [b, Group IbM, and ■b of the periodic table?
It is a metallic element belonging to Group IVb, Group Vb.

Zinc alloys for this purpose are being obtained to a certain level through research, but these zinc alloys are powdered and used in an anhydrous state, or at least at a lower freezing rate than before. However, it has not been found to be as effective in suppressing hydrogen gas generation as conventional frozen zinc powder with a high hydration rate, and has not been put to practical use as a negative electrode active material for commercial alkaline batteries.

[Objective of the Invention] The main object of the present invention is to improve both the chemical composition and physical properties of negative electrode zinc powder or zinc alloy powder for alkaline batteries, compared to those of the prior art. Even when used in an extremely low or anhydrous state, the generation of hydrogen gas within the battery is as low as that of the currently used icing zinc powder, which has a high icing rate, and therefore has good storage characteristics. To provide zinc batteries.

[Summary of the invention] That is, in the method of the present invention, by adding a small amount to zinc and alloying it, multiple types of metallic elements are added that provide a corrosion-preventing effect in an alkaline electrolyte and do not impede the polarization characteristics. When granulating the zinc alloy to a predetermined practical particle size or an average particle size, the atomized zinc alloy powder is heated to an alkaline battery so that the bulk specific gravity is significantly larger than that of conventional products. By using it as a negative electrode active material, it is possible to suppress the generation of hydrogen scum in the battery to a practically sufficient level even when used at a significantly lower freezing rate than conventional products or at no temperature. It is something.

[Embodiments of the invention] The present invention will be described in detail below using Examples.

Table 1 shows a comparison of the hydrogen gas generation rate, bulk specific gravity, average shape index, and zinc oxide content in an alkaline electrolyte between the sprayed zinc alloy powder according to the present invention and the sprayed zinc alloy powder according to the prior art. In Table 1, the hydrogen gas generation rate is 10 Il of a 35% KO)-1 solution saturated with zinc oxide.
10 g of a test sample was immersed in a liquid solution, degassed for 30 minutes under a reduced pressure of several torr, and then the electrolyte surface was filled with liquid paraffin and left at 60° C. for 174 hours. In addition, the average shape index is Q, when the length in the maximum direction of each particle is the button (major axis), and the maximum length in the direction perpendicular to the 9 axes is S (minor axis). This is a shape index that expresses the degree of deformation in terms of slenderness. Atomized zinc powders in practical use include those of various shapes, and it is most simple and practical to use the average shape index to indicate the degree of deformation of these particles.

Most of the commonly used atomized zinc particles have a shape index of about 1.8 to 3.6, and their average shape index is about 2.0 to 2.3. The particle size or particle size distribution shown by classifying a certain powder using a standard sieve and a shaker is approximately the particle size or particle size distribution of the short diameter (S) described above if the classification conditions are appropriate. It is.

Table 1 In Table 1, E is an example of the present invention, A is a conventional example, B, C
is a comparative example. That is, A in Table 1 is a typical conventional product, in which electrolytic zinc with a purity of 4N is granulated by the atomization method in the air, then classified into particles in the range of 100 μm to 300 μm, and then granulated with metallic mercury in a dilute NaO+-1 solution. This is a frozen atomized zinc powder with a freezing rate of 6.5% by weight obtained by freezing. The bulk specific gravity of this item is 3.12 (1・Ko-3
However, this is because the true specific gravity has increased due to the high mercury content, and it is because the true specific gravity is larger than before freezing (
The bulk specific gravity of unfrozen ice is usually about 2.5 g-cnr3 to 2.8 g cm-3.

Next, B in Table 1 is a comparative amount, and a zinc alloy containing 0.20% by weight of lead, 0.18% by weight of gallium, and 0.06% by weight of tin was granulated by the atomization method in the air, and after classification. The powder was treated in a dilute CH3C0OH solution containing the required amount of mercuric chloride and frozen to produce a low hydration atomized zinc alloy powder with a freezing rate of 1.37% by weight. C in Table 1 is also a comparative amount, and after a zinc alloy containing 0.15% by weight of lead, 0.13% by weight of gallium, and 0.25% by weight of indium O' was granulated by an atomization method in the air, 100μm to 30
This is anhydrous atomized zinc alloy powder obtained by classification into a 0 μm range.

Table 1 and E are examples of the present invention, and D is zn-pb-Qa-3n having the same composition as B.
Freezing obtained by granulating a quaternary alloy by atomization in a nitrogen atmosphere, classifying it to a particle size of 100 μm to 300 μm, and then treating it in a dilute CH3C0OH solution containing the required amount of mercuric chloride. It is a low-fragility zinc alloy powder with a ratio of 1.34% by weight. Further, E is Zn − having the same composition as the above C.
The pb-Ga-Jn quaternary alloy was granulated by the atomization method in a nitrogen gas atmosphere and then classified to have a particle size of 1001.
It is an anhydrous atomized zinc alloy powder with a particle size ranging from 1 m to 300 μm.

As can be seen from the hydrogen gas generation rates in Table 1 B and C, the periodic table groups Ib, 1[b, mb, Wb, I
Sprayed zinc alloy powder to which multiple metallic elements selected from the group of elements belonging to group Vb and group Vb are added in an effective combination has a lower freezing rate or no freezing rate when used compared to conventional products. As such, hydrogen gas generation is greatly reduced. In other words, with atomized zinc powder having a purity of 4N and produced in the same manner as the electrolytic zinc powder, the hydrogen gas generation rate is several tens of times higher than the value at 60°C in Table 1 G even at a test temperature of 45°C in the case of non-oxidizing. This is because it shows that

However, it can be seen that the amount of hydrogen gas generated is still large compared to the conventional products with a high freezing rate shown in Table 1A. On the other hand, in the case of the zinc atomized alloy powder of the present invention, which is shown as E in Table 1 and has a large bulk specific gravity, it is used at a low or non-grading rate of 1.34% by weight. It can be seen that the hydrogen gas generation rate is halved compared to B and C, and the ice formation rate is close to that of the conventional example. In addition to the examples of alloy compositions shown in Table 1, F, Group Ib, Group Ib, and Group 1 [
A metallic element selected from the group of elements belonging to Group b, Group Wb, Group 1), such as Pb, T1. Ga.

Sprayed zinc alloy powders made of other component compositions in which two or more of ln, cd, 3n, 3i, etc. are effectively combined and added in appropriate amounts can also be atomized and granulated using vacuum or inert gas, etc. Examples were also carried out in which the bulk density was increased by a method such as carrying out in a non-oxidizing atmosphere, and almost the same effect as E was obtained.

The reason why the atomized zinc alloy particles having a large bulk specific gravity in the present invention generate less hydrogen gas in an alkaline electrolyte when the particle size is approximately the same has not been fully elucidated. However, when viewed under SEM, differences in particle shape as shown in the drawings are observed. FIG. 1 shows a particle shape model of the atomized zinc alloy powder according to the present invention, and FIG. 2 shows a particle shape model of the conventional powder. In each figure, (a) is the one with a large particle size, (
b) is a shape model with a small short axis.

The atomized zinc alloy particles of the present invention shown in Fig. 1 have significantly fewer sharp parts in the particle shape than the conventional product shown in Fig. 2, and the particle ends are rounded as a whole. Almost no wrinkle-like pattern is observed on the surface.

In addition, the particles with small particle diameters are more similar to spheres than the conventional products, and there are many particles with a shape index close to 1.0. Corresponding to this change in shape, the average graininess index is also 1.8 or less in the case of the present invention, compared to about 2.0 to 2.3 in the conventional case. These changes in shape are thought to be the main reason for increasing the bulk specific gravity, but at the same time, it has been recognized that the powder flow rate is also improved because it reduces friction between particles and makes it difficult to form bridges. There is.

Further, as shown in Table 1, the zinc oxide content of the atomized zinc alloy powder having a large bulk specific gravity is extremely small. If the zinc oxide content is excessive, it will not affect the hydrogen gas generation rate much, but it will easily cause variations in the hydrogen gas generation electrode.
In particular, when used in alkaline batteries, the properties under severe usage conditions, such as rapid discharge properties and pulse discharge properties at low temperatures, may be degraded.

Furthermore, since zinc oxide is a reaction product of batteries, and its excessive content means a decrease in the amount of active material, it is desirable that its content be as small as possible.

[Effects of the Invention] From the following observations, the effects of the present invention can be considered as follows. In other words, from a transient phenomenon point of view, in the conventional case, molten zinc or molten zinc alloy extruded from a nozzle is rapidly and simply deposited on the surface of metal particles in the form of clean droplets immediately after being atomized by air blow. An oxide film with a thickness of a molecular layer or more is produced. The formation of an oxide film changes the interfacial tension of the liquid metal particles, and the individual particle shapes cool and solidify below the melting point before they are sufficiently affected by agglomeration due to the interfacial tension. Particles with various irregular shapes are produced depending on acceleration, direction, gravity, etc., and sharp edges are likely to be formed at the ends of the particles. In addition, the formation of wrinkle-like patterns on the surface of metal particles occurs because liquid metal particles with an oxide film formed on the surface change shape every moment as they cool and solidify, and each time the oxide film on the surface is broken and a fresh metal is formed. It is thought that it was produced by repeatedly exposing a surface and then covering it again through re-oxidation.

On the other hand, in the case shown in Example N of the present invention, molten zinc or molten zinc alloy extruded from a nozzle is sprayed into an inert gas atmosphere with high-pressure nitrogen gas, and when it is granulated, it becomes a liquid. Since the surface of the alloy particles undergoes little or no oxidation, they are easily susceptible to agglomeration9 and spheroidization due to interfacial tension, and are also susceptible to the effects of acceleration and gravity until the particles are cooled below their melting point and solidified. It is thought that small particles are likely to become spherical.

For particles with a large radius, it is difficult for the particle shape to become spherical as a whole due to the influence of gravity, etc., and it is easy to become irregular in shape.
Locally, the edges of the particles become rounded and the sharp angles are reduced, so the shape index becomes small. Furthermore, the particle surface is not affected by the oxide film, so it becomes a relatively smooth surface. From these results, it seems that the average shape index becomes smaller, the friction between particles decreases, improving fluidity and increasing the bulk specific gravity. In addition, these changes bring about some changes in the state of alloy crystals and grain boundaries, as well as in the segregation behavior of unavoidably contained impurity elements and effective additive elements in grain boundaries, and as a result, the hydrogen overvoltage of the sprayed zinc alloy powder according to the present invention increases. It seems that he is in a serious situation. In any case, it has been found that such changes in preferable properties can be collectively managed using the bulk specific gravity, since they correlate with changes in the bulk specific gravity.

As described above, the present invention provides a zinc alloy in which an appropriate amount of multiple metallic elements belonging to Group 1L, Group IIb, Group Mb, Group Wb, and Group B of the Periodic Table are effectively combined and added. By using atomized zinc alloy powder formed to have a bulk specific gravity of 3.5 g/am-3 or more in the practical particle size range as the negative electrode active material, a low hydration rate or zero mercury content with a mercury content of 2% or less can be achieved. When used in the alkaline electrolyte, the amount of hydrogen gas valve element in the alkaline electrolyte is extremely small, and therefore an alkaline battery with good storage characteristics and environmentally friendly properties can be provided. In addition, by using powder with a high bulk density, the amount of active material in the same negative electrode volume can be increased, and rapid discharge characteristics at low temperatures can be improved. This method has great industrial effects, such as being able to obtain a gelled zinc negative electrode with little variation in the weight filled in the battery during measurement.

The zinc alloy powder of the present invention which has low or no gradient has a so-called gel method in which a gelled zinc mixed with an alkaline electrolyte and an arbitrary gelling agent is used as a negative electrode, and a gelling agent is mainly provided on the surface of the zinc alloy particles. A thin layer is formed and then gelled by injecting an alkaline electrolyte into the negative electrode container.
It can be applied to any Qel method.

The technology of the present invention also applies to silver peroxide batteries and silver oxide batteries.

Nickel/zinc batteries, alkaline/manganese batteries.

It is effective when applied to alkaline batteries of various structures (cylindrical, button, coin, ultra-flat, etc.) that use zinc as a negative active material, such as air/oil-lead batteries.

[Brief explanation of drawings]

FIG. 1 is a particle shape model of particles constituting the atomized zinc powder of the present invention, and FIG. 2 is a particle shape model of particles constituting a conventional atomized zinc alloy powder. Each figure (a)
(b) shows the particle shape of a large particle size, and (b) a small particle size. Figure 1 2 @ (b) (b) Procedural amendment @ (method) % formula % [ 1. Indication of the case 1982 Patent Application No. 104675 2. Title of the invention Alkaline Zinc Battery 3. Person making the amendment Relationship to the case Patent applicant Address: Toshibasonde 4, 3-4-10 Minamishinayo, Tokyo Parts Co., Ltd. Date of amendment order: August 8, 1980

Claims (3)

[Claims] (1) In an alkaline battery using zinc alloy powder as a negative electrode active material, the zinc alloy powder is
Zinc alloy containing two or more metallic elements arbitrarily selected from the group of elements belonging to Group IIb, Group IIIb, Group IVb, and Group Vb, and has a hydrogenation rate of 2% by weight or less. An alkaline-zinc battery characterized by using a sprayed zinc alloy powder having low or no gradation and having a bulk specific gravity of 3.5 g·cm^-^3 or more. (2) The alkaline zinc battery according to claim 1, wherein the atomized zinc alloy powder has an average shape index of 1.8 or less. (3) The alkaline zinc battery according to claim 1, wherein the zinc oxide content of the atomized zinc alloy powder is 0.2% by weight or less.