JPS59175558A - Alkali cell - Google Patents

Abstract

PURPOSE:To prevent gas generation in alkali cell while it is stored, by using a zinc negative electrode which is provided by zinc powder with tellurium deposited on the surface thereof and free from mercury. CONSTITUTION:A zinc negative electrode 4 of zinc powder with tellurium existing on the surface layer thereof and free from mercury is used. The tellurium concentration should preferably be 0.01-0.1% by weight to the zinc powder. By way of example, 100pts. of zinc powder is mixed with a solution of 0.18pt. of orthotelluric acid (H6TeO6) dissolved in 100pts. of water, at 20 deg.C; the mixture is then held for 24hr gently shaken, whereby the tellurium ion in the water solution is substitutionally deposited as Te on the surface of the zinc in the proportion of approximately 0.1%; and the same is washed and dehydrated and thereafter mixed with an electrolyte composed of about 37% of KOH, 4.5% of ZnO, 1.5% polyacrylic sodium, and remaining portion of water, whereby the negative electrode 4 is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to the use of non-amalgamated zinc powder in a zinc negative electrode in a battery having an alkaline electrolyte.

Although zinc is highly reactive, it has a low hydrogen overvoltage, so it reacts with the electrolyte during long-term storage of the battery and tends to self-corrode according to the following reaction formula.

Zn + 40H-→Zn(OH); + :2e-2
H, O+2e-→20H-+ H2↑Hydrogen gas generated by self-corrosion increases the gas pressure inside the battery, which has the problem of lowering the reliability of the airtightness of the battery seal.

For this reason, a commonly adopted method is to add mercury to zinc powder to utilize the hydrogen overvoltage on the mercury surface, thereby preventing self-corrosion of zinc.

That is, an amalgam zinc powder containing 6 to 10% by weight of mercury was used.

However, the addition of 6 to 10% by weight of mercury, which is not directly related to the negative electrode reaction, deteriorates the weight efficiency of the zinc negative electrode, and there has been a desire to improve this point.

In addition, as a solution to these problems, the idea of preventing self-corrosion by using an alloyed zinc powder made by adding gallium, indium, lead, etc. to zinc was proposed, but zinc has a low melting point and is generally homogeneous with other elements. Since it is difficult to obtain a good condition, this method still has problems with self-dissolution (gas generation) during battery storage.

This invention prevents gas generation during storage in alkaline batteries by using a zinc negative electrode with tellurium deposited on the surface of zinc powder to which mercury is not added.

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows an example in which the present invention is applied to an LR6 type alkaline battery.

In the figure, reference numeral 1 denotes a metal container, into which a cylindrical positive electrode mixture 2 containing manganese dioxide and zinc is filled under pressure.

The hollow part of this positive electrode mixture 2 is filled with a negative electrode 4 mainly made of zinc through a separator 3 made of a nonwoven fabric of fine polypropylene fibers having excellent alkali resistance.

A negative electrode terminal 7 is provided, and the metal container 1 is covered with a metal outer can 9 via an insulating tube 8.
Fold the upper opening inward to press the periphery of the negative electrode terminal 7, and bend the lower opening inward to form the positive electrode terminal plate 1.
By pressing the bottom surface of the metal container 1 through the metal container 1, the battery is sealed and the battery is completed.

In this case, the negative electrode 4 is orthotelluric acid (H, T ea
. ) 0.18 parts dissolved in 100 parts of water is mixed with 100 parts of zinc powder at 20°C, and then the tellurium ions in the aqueous solution are precipitated on the zinc surface by holding the mixture for 24 hours while shaking gently. It is.

After 24 hours of gentle shaking, tellurium ions ionized from 0.18 parts of orthotelluric acid are precipitated on the zinc surface at a rate of approximately 0.1% as Te, which is thoroughly washed after 24 hours. After that, the water was removed and the mixture was mixed with an electrolytic solution consisting of about 37% KOH, 4.5% Zn, 1.5% sodium polyacrylate, and the balance water.

As the tellurium deposited on the zinc surface is rubbed against each other by shaking, the deposited tellurium is homogenized, which also has the effect of homogenizing the surface potential of the zinc powder surface. Yes, as shown in Table 1, LFL
6 The amount of gas generated after storage of the battery was the same as that of a conventional battery using mercury, which was a very effective result.

After storing 50 JIS name LR6 type alkaline batteries of conventional battery C using silver and conventional battery B without adding mercury to zinc powder in a storage room at 60°C, the amount of gas in the battery was determined after a specified period of time. This shows the measured values collected in water.

In addition, as a result of various tests regarding the amount of tellurium bent on the surface of zinc powder, it was found that it was 0.01% by weight based on the weight of zinc powder.
The effect was observed above, and no corrosion prevention effect was observed at less than 0.01% by weight.

Moreover, if the amount exceeds 1.0% by weight based on the zinc powder, the battery voltage will drop significantly, which is not desirable or desirable. Therefore, the preferred range of tellurium amount is 0.01 to 1.0% by weight in the zinc powder.

In addition to the wet method, methods for depositing zinc powder on the zinc powder surface include a dry method that does not use a solvent, such as a sputtering method on the surface of the zinc powder, and a method of irradiating the surface of the zinc powder with an accelerated tellurium ion beam. A doping method according to the method is also effective.

Therefore, according to the present invention, by using a gel-like negative electrode using zinc powder in which tellurium is present in an amount of 0.01 to 1.0% by weight based on the weight of the zinc powder on the surface of the zinc powder, battery storage is possible. It is possible to prevent self-discharge of zinc inside the battery and gas generation inside the battery after storage, which reduces the reliability of battery sealing caused by increased gas pressure inside the battery. It is possible to make a product with high marketability without causing any damage.

[Brief explanation of drawings]

FIG. 1 is a sectional view of an alkaline battery showing an embodiment of the present invention. - 1... Metal container 2... Positive electrode mixture 3...
Separator 4... Negative electrode 5... Insulating gasket 6... Current collector rod 7... Negative electrode terminal 8...
Insulating tube 9...Exterior can 1o...Positive terminal plate Name of patent applicant Toshiba Battery Corporation No. 114

Claims (2)

[Claims] (1) An alkaline battery using a mercury-free zinc negative electrode with tellurium present in the zinc powder surface layer. (2) The alkaline battery according to claim 1, wherein the concentration is 0.01 to 0.1% by weight based on the zinc powder.