JPS6110859A - Alkaline-zinc battery - Google Patents

Abstract

PURPOSE:To reduce hydrogen gas generation inside an alkaline-zinc battery as well as to aim at improvements in a storage characteristic, by using zinc alloy powder being low amalgamation unamalgamation, specifying amalgamation rate, zinc oxide content and bulk specific gravity, as a negative active material. CONSTITUTION:In case of an alkaline battery, zinc alloy powder of low analgamation or unamalgamation being below amalgamation rate 3wt%, below zinc oxide content 0.3% and more than bulk specific gravity 3.4g/cm<-3> is used for a negative active material. According to this alkaline battery, hydrogen gas generation inside the battery is restrainable as much as the same degree as that using zinc dust of the conventional amalgamation rate. In additional active material quantity in the same negative capacity is increasable and, what is more, a rapid discharge characteristic in time of low temperature is improvable.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a zinc negative electrode used in an alkaline electrolyte containing an alkali metal hydroxide as the main electrolyte with a low concentration ratio or in an anhydrous state. .

[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%) or higher. Zinc powder consisting of a group of irregularly shaped particles obtained by atomizing high-purity electrolytic zinc using the atomization method, with a particle size (minor axis) of about 60 μm to 350 μm, and a shape index of 2.0 to 2.3. degree, zinc oxide content 0.
It is about 2% by weight to 0.3% by weight.

[Problems in the background art] Such zinc powder has a low hydrogen overvoltage in an alkaline electrolyte, and also has a relatively low chemical polarization when discharged in a battery where the amount of electrolyte is actually extremely limited. Because of the large size of the battery, it is usually used after being frozen to various degrees depending on the type of battery, construction, and purpose of use.In this case, the freezing rate t is The weight ratio of the bulk is in the range of 5% to 25% by weight, and those having a culm of 6% to 12% by weight are particularly frequently used.

In addition, the zinc oxide content is 0.4% by weight to 0.9% by weight.
In many cases, it is about % between molds.

The presence of a large amount of mercury in the negative electrode is undesirable because it inevitably leads to a decrease in the amount of active material within the volume that the negative electrode is designed 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 methods for doing so are mainly chemical methods, such as zinc alloy composition, surface treatment of zinc particles, and changes in alkaline electrolyte. corrosion inhibitor (l nh
ibitor), etc.

Attempts for this purpose have been achieved to a certain degree in research, but zinc or zinc alloys are powdered and used in a non-oxidized state, or at least at a lower percentage of oxidation than in the past. However, it has not been found to be as effective in suppressing hydrogen gas generation as the conventional frozen zinc powder with a high degree of oxidation, and has not yet been put into practical use as a negative electrode active material for commercial alkaline batteries.

[Objective of the Invention] The object of the present invention is to improve the physical properties of zinc powder or zinc alloy powder used in the negative electrode of alkaline batteries, thereby making the zinc powder or zinc alloy powder lower or less resistant than those of the prior art. To provide an alkaline-zinc battery that generates as little hydrogen gas within the battery as the currently used frozen zinc powder with a high degree of oxidation even when used under conditions of .

[Summary of the Invention] In other words, in the present invention, by adding a small amount to high-purity zinc or zinc with an unavoidable contamination element, especially iron content as low as possible, and alloying it, a corrosion-preventing effect is brought about in an alkaline electrolyte, and When using a zinc alloy to which metallic elements are added that do not inhibit polarization characteristics, and when granulating the zinc or zinc alloy to a practical predetermined particle size or average particle size, it is bulkier than conventional products. By using atomized zinc alloy powder with a significantly increased specific gravity as the negative electrode active material of alkaline batteries, even when used at a lower rate of oxidation or no oxidation compared to conventional products, the ( ]
This makes it possible to suppress hydrogen gas generation to a practically sufficient level.

[Example of explanation] 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 determined by immersing 10 (l) of the test sample in 10 m of a 35% KOH solution saturated with zinc oxide, degassing it for 30 minutes under a reduced pressure of several torr, and then Filled with liquid paraffin and left at 60°C for 174 hours.The average shape index is the length of each particle in the maximum direction (major axis), and the maximum length in the direction perpendicular to the axis. When S (minor axis) is defined as S (minor axis), i/s is the shape index that expresses the degree of deformation of the particle in terms of slenderness.Practical atomized zinc powder includes a variety of shapes. It is simplest and most practical to use the average shape index to indicate the degree of deformation of these particles.The shape index of the commonly used atomized zinc particles is mostly around 1.8 to 3.6. , its 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 an S 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 something.

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 mixed with metallic mercury in a dilute NaOH solution. This is frozen zinc powder with a viscosity of 6.5% by weight.

The bulk specific gravity of this thing before freezing (unfrozen) is usually 2.5.
g-cnr3 to about 2.8 gcm-3.

Next, B in Table 1 is a comparative amount, in which electrolytic zinc with a purity of 4N was granulated by the atomization method in the air, and after classification,
This is a low filtration zinc alloy powder with a filtration rate of 2.81% by weight, obtained by treating a dilute CH3C0OH solution containing the required amount of mercuric chloride and freezing it.

C in Table 1 is also a comparative amount! This is an amorphous zinc alloy powder obtained by atomizing a zinc alloy containing 10.15% by weight and 0.13% by weight of gallium in the air by an atomizing method, and then classifying the powder into particles in the range of 100 μm to 300 μm.

In Table 1, E to E are examples of the present invention, and D is the same as B above, granulated electrolytic zinc with a purity of 4N by the atomization method in a nitrogen atmosphere and classified to have a particle size of 100 μm. to 300 μm, and then treated in a dilute CH3CO0H solution containing the required amount of mercuric chloride. This is a low filtration zinc alloy powder with a filtration rate of 2.85% by weight. Further, E is a non-aqueous zinc alloy powder which is made by granulating a Zn-Rb-Ga ternary alloy having the same composition as C above by an atomizing method in a nitrogen gas atmosphere, and then classifying the powder to have a particle size in the range of 100 μm to 300 μm. It is.

In the case of the zinc alloy powder of the present invention, which has a high bulk specific gravity as indicated by E in Table 1, the bulk specific gravity is small even when it is used with a low water conversion rate of 2.85% by weight or with no water content. B, C
It can be seen that the hydrogen gas generation rate is significantly reduced compared to the above. Furthermore, E can further reduce the rate of hydrogen gas generation by freezing it to a low aging rate of 1 to 3% by weight.

The reason why the 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 substantially the same has not been fully elucidated. However, according to 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 zinc alloy grains of the present invention shown in Fig. 1 have significantly fewer sharp angles in the particle shape than the conventional product shown in Fig. 2, and the particle ends are rounded as a whole, and the particle surface There is hardly any wrinkle-like pattern formation 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.

Furthermore, as shown in Table 1, zinc alloy powders with large bulk specific gravity have a significantly low zinc oxide content.

The zinc oxide content does not significantly affect the hydrogen gas generation rate if it is not excessive, but it tends to cause variations in the amount of hydrogen gas generated, and especially when used in alkaline batteries, the characteristics under harsh usage conditions, such as rapid discharge characteristics at low temperatures. This may cause the pulse discharge characteristics to deteriorate.

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 above observations, the effects of the present invention can be considered as follows. In other words, from a transient phenomenon perspective, in the conventional case,
Immediately after the molten zinc or molten zinc alloy extruded from the nozzle is atomized by air blowing, an oxide film of a monomolecular layer or thicker is rapidly formed on the surface of the clean droplet-shaped metal particles. . The formation of an oxide film changes the interfacial tension of liquid metal particles, and the shape of each particle cools to below the melting point and solidifies before it is sufficiently affected by agglomeration due to the interfacial tension. Particles with various irregular shapes are produced depending on the acceleration/direction of n@, gravity, etc., and sharp parts 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 move until they solidify in the cold. It is thought that the metal surface was exposed and that part was repeatedly oxidized.

On the other hand, in the case shown in Example 1 of the present invention, molten zinc or molten zinc alloy pressed out from a nozzle is sprayed into an inert gas atmosphere with high-pressure nitrogen gas, and when granulated, it becomes a liquid. Since the alloy particle surface undergoes little or no oxidation, it is easily susceptible to the effects of agglomeration and spheroidization due to interfacial tension, and is less affected by acceleration and gravity until the particles are cooled below their melting point and solidified. It is thought that fine particles are easily 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 changes. It seems that it is making the . In any case, it has been found that such changes in preferable characteristics are correlated with changes in bulk specific gravity, and can therefore be collectively managed based on bulk specific gravity.

As described above, the present invention provides high purity zinc or a zinc alloy to which a metallic element is added which provides a corrosion-proofing effect in an alkaline electrolyte by adding a small amount to zinc and alloying it, and which does not impede the polarization characteristics. When granulating the zinc or zinc alloy to a practical predetermined particle size or average particle size, the zinc powder or zinc alloy powder whose bulk specific gravity is significantly larger than that of conventional products is treated with an alkali. By using it as a negative electrode active material in a battery, it is possible to suppress the generation of hydrogen gas within the battery to a considerable extent even when the battery is used at a lower rate of oxidation or no oxidation than before. In addition, by using a powder with a large bulk density, the amount of active material can be increased in the same C negative electrode volume, improving rapid discharge characteristics at low temperatures, and improving handling workability in the battery manufacturing process. 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. 71I layer is formed in advance, and this is gelled by injecting an alkaline electrolyte in the negative electrode container, so-called Powder with.
It can be applied to any Gel 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 the negative electrode active material, such as air-zinc batteries.

[Brief explanation of the drawing]

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 the conventional atomized zinc alloy powder. Each figure (a7 shows the particle shape of a large particle size, (b) shows the particle shape of a small particle size. Figure 1 Figure 2 (Q) (η) (b) Cb) Procedure correction steel (
Method) % formula % 1, Indication of the case Patent Application No. 104674 of 1982 2, Name of the invention Alkaline Zinc Battery 3, Relationship with the person making the amendment Patent applicant address 14g Shinagawa Gminami Shinagawa Address Tokyo Parts Toshibasonde No. 3-4-10 Minamishina - Name (353) Toshiba Battery Co., Ltd. 4 Date of amendment order August 8, 1980

Claims (2)

[Claims] (1) In an alkaline battery using zinc alloy powder as the negative electrode active material, the zinc alloy powder has a viscosity rate of 3% by weight or less, a zinc oxide content of 0.3% by weight or less, and a bulk specific gravity of 3.4g. An alkaline zinc battery characterized in that it uses a zinc alloy powder with low or zero flux of at least cm^-^3. (2) The alkaline zinc battery according to claim 1, wherein the zinc alloy powder has an average shape index of 1.8 or less.