JPS6177265A - Zinc alkaline battery - Google Patents

Abstract

PURPOSE:To obtain a low amalgamated zinc negative electrode having high corrosion resistance and good discharge performance by alloying zinc with a specified amount of Al and/or Mg, and adding a specified amount of In and at least one of Pb, Cd, and Sn to the zinc alloy. CONSTITUTION:Zinc alloy containing 0.05-0.5wt% indium, total 0.01-0.5wt% at least one of lead, cadmium, and tin, and total 0.005-0.2wt% aluminium and/or magnecium is used as a negative electrode 2 of a zinc alkaline battery. Since Al and Mg in the zinc alloy has lower potential than zinc, discharge utilization factor of zinc is increased. Indium in the zinc alloy increases hydrogen overvoltage of zinc alloy and moreover increases corrosion resistance of the zinc alloy by synergetic effect with Pb, Cd, and Sn.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention uses zinc as a negative electrode active material, an alkaline aqueous solution as an electrolyte, and manganese dioxide, silver oxide, or silver oxide as a positive electrode active material.
This invention relates to improvements in zinc-alkaline batteries using mercury oxide, oxygen, etc.

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 5 to 10% by weight of mercury to zinc, and to suppress corrosion to the extent that there is no practical problem. . However, in recent years, there has been an increasing social need to reduce the amount of mercury contained in batteries in order to reduce pollution, and research on type 2 is being conducted. For example, 11 in zinc
),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 products cover the active zinc surface and the hydroxide ions necessary for the discharge reaction are transferred to the zinc surface. This is thought to be due to the fact that the degree of blockage of mercury supply is greater than when the mercury content is high, and the establishment of a low-density zinc negative electrode that has both corrosion resistance and strong discharge performance is an important issue for the future.

In addition, with the aim of improving manganese dry batteries, there is a proposal that using zinc or a zinc alloy with indium added to the zinc alloy for the negative electrode has a large anti-corrosion effect (Japanese Patent Publication No. 33-3204). .

Among the above proposals, in addition to indium, Fe, Cd, Cr, Pb, Ca, and H are used as elements in the zinc alloy.
g.

Bi, Sb, AI, Ag, Mg, Si, Ni, Mn, etc. are described as impurities or additives, including cases where I or two or more types are included, or when indium onboard is used together as an additive element. Other than their effectiveness, there is no indication of whether they contain the miscellaneous elements listed above as impurities or are added as effective elements, and it is not even clear whether these elements are effective in preventing corrosion. Indium for proper addition amount.

There is no mention of anything other than lead. The effects of ♀11 synthesis of these elements, and the determination of an effective alloy composition by examining this in a zinc-alkaline battery, remain as future issues.

Problems to be Solved by the Invention As mentioned above, there is a need for a zinc negative electrode for Akinonori batteries that has a low hydration rate, high edibility and strong discharge performance.

3. The present invention has a negative electrode zinc corrosion resistance of 1'1", a reduction in the water rate without deteriorating the bV electrical performance, low pollution, discharge performance, storage performance, and In and I leakage properties. Means for solving the problems of alkaline battery systems (11+ low performance zinc) The present invention provides an electrolyte containing an aqueous solution containing caustic glue, or 11-soda as a main component. ) 1η, use zinc as the negative electrode active material, manganese dioxide, silver oxide, mercury oxide, oxygen, etc. as the positive electrode active material. 5 weight δ,
#;) (Pb), horn 1~mium (Cd), tin (Sn
) or (''2 or more -1- elements together) 0.01
~0.5% by weight, AJ Reminium (81).

It is characterized by using a zinc alloy containing one or two elements of magnesium (tVlg) in a total amount of 0.005 to 0.02%.

Effects of the present invention Firstly, the discharge reaction product coats the active tf zinc surface, and 1) the hydration rate tends to be particularly low because it impairs the f11 supply of acid ions and prevents the discharge reaction from proceeding smoothly at large currents. AI,
The problem was solved by adding an appropriate amount of an element selected from 1g of h.
At the same time, an appropriate amount of an element selected from the group consisting of Pb, Cd, and Sn is added to further synergistically enhance the anticorrosion effect of In, resulting in a low water content with excellent J stiffness, corrosion resistance, and discharge performance. This is the realization of a zinc negative electrode.

''As shown in the examples below, the effects of adding AI and Mg are effective when added in appropriate amounts, and the mechanism of their action has not been fully elucidated. Presumably, AI and Mg contained in the zinc alloy of the negative electrode have a more base potential than zinc, and are discharged together with zinc, resulting in the dissolution of the discharge products of zinc into the electrolyte. The discharge that depletes zinc creates a state in which hydroxide ions are abundantly supplied to the active surface of zinc, and serves to promote the zinc surface passivation due to the densification of the undissolved product layer. It is considered to be possible to maintain it continuously until the end of the stage and increase the discharge utilization rate of A11).

In addition, In is known as one of the most effective additive elements for corrosion prevention among all elements, but it is possible to further enhance the corrosion prevention effect by combining with other additive elements. can.

The effect of adding In is that it has the effect of increasing the hydrogen perelectron in the zinc alloy91 and has a large affinity with mercury11, so the mercury added for hydration is fixed on the surface and grains W of the zinc alloy, and the crystals are It is thought that a greater corrosion-preventing effect can be obtained by suppressing the diffusion of mercury into the inside of the zinc alloy and maintaining a high mercury concentration on the surface and the inside of the zinc alloy by adding a small amount of mercury.

In the present invention, Cd, S
Since n has a relatively low affinity for mercury, the presence of these elements in the grains W of the zinc alloy suppresses the diffusion of mercury in the zinc alloy, which has hydrated from the surface, from the surface layer to the grain boundaries. Since JfF is effective in maintaining a high surface concentration of mercury, it is determined that JfF exhibits a synergistic anticorrosion effect with In.

In addition, in the present invention, ＼1. The main effect of adding Mg is the discharge 11. However, depending on the amount added, it also has a slight effect on increasing the anticorrosion effect of other elements listed in "1-1-". When corroded by electrolyte, since it is a base metal than zinc, it is easily oxidized preferentially to zinc, and forms an oxide film that inactivates the active sites on the surface of the zinc alloy, suppressing corrosion. It is thought that it has some effect, but if it is added in more than the amount necessary to form the oxide film mentioned above, it will corrode preferentially to the excessively added element or zinc, which will actually increase the generation of hydrogen gas. considered to be a thing.

As described above, in the present invention, we have experimentally investigated the combination and amount of added elements in the zinc alloy used for the negative electrode, and have achieved a zinc negative electrode with a low water conversion rate that combines discharge performance and corrosion resistance. be.

Examples Various zinc alloys were prepared by adding various elements as shown in the table later to zinc ingots with a purity of 99.997% or more.
Melt it at 00℃ and inject it with compressed air to powder it,
The particles were sieved to a particle size ranging from 0 to 150 mesh to 7-. Next, the above-mentioned powder was put into a 10% by weight aqueous solution of caustic sardine, and a predetermined amount of mercury was added dropwise with stirring to freeze it. Thereafter, it was washed with water and replaced with acetone to prepare a dried L, fertilized Ti) alloy powder. Further, hydrated aluminum 1;) Alloy powder other than the examples of the present invention was prepared using the same method as a comparative example of monomerization.

Using these hydrated powders, the button-shaped silver oxide battery shown in the figure was manufactured. In the figure, I is a sealing plate made of stainless steel, and the inner surface is coated with copper plating. 2 is a zinc 1) electrode in which an electrolytic solution containing a 40% by weight aqueous solution of caustic glue saturated with zinc oxide is gelatinized with carboxymethyl cerolose, and hydrated powder is dispersed in the gel. 31
11 is a separator made of porous polypropylene, 5 is a positive electrode formed by mixing black 81) with silver oxide, and 6 is a positive electrode made of iron with niso'r)I plating. The positive electrode ring, 7, is a positive electrode can made of stainless steel, and the inner four surfaces are coated with (Nira-buki plating). 8 is a polypropylene gasket, which is compressed between the positive electrode ring and the sealing plate when the positive electrode can is bent. The prototype battery has a diameter of 11.6 mm and a height of 5.4 mm, the weight of the hydrated powder of the negative electrode was unified to 193 mg, and the amount of mercury added (
The hydration rate) was 1% by weight based on the zinc alloy powder. The following table shows the composition of the zinc alloy of the prototype battery, and the changes in discharge performance and total battery height after storage at 60°C for one month. The discharge performance was expressed as the discharge duration when discharging at 20° C. at 510Ω with a final voltage of 0.9V.

1 Yu/1 station!・ 1. As seen in this table, compared to the conventional case where only In was added (tooth 1), Pb, Cd or Sn was added to I
When added together with n (interval, 3,5.6>), the expansion of the battery is smaller and the corrosion resistance is improved as a synergistic effect.However, it is not true that In is the element that strongly controls the corrosion resistance. For example, it is clear from the comparison between NO2 and Separation 3.

Furthermore, as shown in gaps 4 and 8, if too many elements are added to improve corrosion resistance, it will have the opposite effect. Among these conventional examples, if the battery expands significantly, the discharge performance may be poor.For example, even if the battery is judged to have sufficient corrosion resistance, such as Nn3, 5.6, the duration under heavy load discharge of 510Ω is As described later, it is shorter than the product of the present invention. On the other hand, when one or both of AI and Mg are simultaneously added as additive elements with the main purpose of increasing the corrosion resistance due to the combined effect of these additive elements and smoothing the discharge reaction of the negative electrode (
~32), discharge performance.

It is judged that both corrosion resistance has been improved over the conventional example.
0.01-0.5% by weight of In, Pb, Cd.

A total of 0.01 to 1 or more elements of Sn
0. When a zinc alloy containing a total of 005 to 0.2% by weight of one or two elements of AI and Mg is used (N], IO,1).

12, +5.16.18,19,20,21°22.2
3,25,27,28.30), and if the amount of added elements is insufficient or excessive, 1+, 9,13°14.17,24
．． 2G, 29.3]) has a slight combined effect, which is not much different from the relatively good conventional examples, but on the contrary, it has the opposite effect. A remarkable effect is observed.

As described above, the present invention provides one of the additive elements having a large corrosion resistance effect.
11 and at the same time, by containing an appropriate range of elements whose main purpose is to facilitate the discharge reaction, a zinc-alno-J battery with low pollution and excellent practical performance was realized.

In addition, in the examples, a battery using a zinc chloride negative electrode was explained, but in an air battery or a sealed zinc-alkaline battery equipped with a hydrogen absorption mechanism, the permissible amount of hydrogen gas generated is relatively large. , -14= When the present invention is applied to such a case, the water reduction rate may be lowered, and depending on the case, it may be carried out with the water being made anhydrous.

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

[Brief explanation of drawings]

The figure is a partially sectional side view of a button-shaped silver oxide battery used in an example of the present invention. 2... Zinc negative electrode, 4... Separator, 5... Silver oxide positive electrode.

Claims (1)

[Claims] 0.01 to 0.5% by weight of indium, 0.01 to 0.5% by weight of one or more of lead, cadmium, and tin;
0.0 of one or both of aluminum and magnesium
A zinc alkaline battery using a zinc alloy containing 0.05 to 0.2% by weight as a negative electrode active material.