JPH07169463A - Alkaline battery - Google Patents

Abstract

PURPOSE:To further improve the discharge characteristic of a mercury-free alkaline battery, and particularly enhance the capacity at low temperature discharge and high load discharge. CONSTITUTION:This battery contains no mercury and has, a negative electrode active material, a zinc-based alloy to which a trace amount of one kinds or more of lead, indium, aluminum, gallium, tin, calcium, magnesium, bismuth, lithium, sodium, etc., are added. The particle size of the zinc-based alloy powder ranges from 75 to 540mum, and those having particle sizes less than 300mum account for 90% or more.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an alkaline battery using a zinc powder (to be exact, a zinc-based alloy powder to which a trace amount of alloying elements is added) as a negative electrode active material, and in particular, zinc powder is amalgamated with mercury. The present invention relates to a technique for improving characteristics of a so-called silver-free alkaline battery, which has been eliminated.

[0002]

2. Description of the Related Art As is well known, zinc powder for alkaline batteries is usually produced by an atomizing method and has a particle size of about 75 to 450 μm, and most of them have a potato-like particle shape (comparison). It is usually a mixture of potato-shaped and round sweet potato-shaped ones). Since zinc in the form of powder having a large surface area is used for the negative electrode, it has excellent reactivity in the electrolytic solution, and therefore this type of alkaline battery is suitable for high current discharge. On the other hand, because of the large surface area, the negative electrode zinc is easily corroded in the electrolytic solution, and conventionally, a large amount of mercury has been used to maintain the corrosion resistance. However, due to concern over the environmental pollution problem of mercury in waste dry batteries, technical improvements have been made to reduce mercury in alkaline batteries and to make them silver-free.

The amalgamation of zinc powder with mercury is abolished, and instead, a zinc-based alloy powder containing a trace amount of a suitable alloying element is used as the negative electrode active material, thereby improving its corrosion resistance and battery characteristics. From this point of view, extensive research has been conducted and a number of alloying elements effective for corrosion prevention have been found. For example, lead, indium, aluminum, gallium, tin, calcium, magnesium, bismuth, lithium, sodium, etc. (However, there is a concern about environmental pollution problems with lead, so it is being used as little as possible). A lot of meaningful data has been accumulated on matters such as what and how much of these alloy elements should be added, and which elements and which elements should be added together to obtain a large synergistic effect. As a result, a mercury-free alkaline battery that is practically practical is being realized.

[0004]

The current mercury-free alkaline battery has some inadequacies in characteristics as compared with the conventional alkaline battery using mercury. One of them is that the discharge performance at low temperature is much lower than that at normal temperature. Further, there is a problem that the capacity at the time of high load discharge is small. Discharge between a conventional alkaline battery (hereinafter referred to as a mercury-containing alkaline battery) that uses zinc amalgamated zinc powder containing 250 ppm of mercury and an anhydrous silver alkaline battery that uses a zinc-based alloy powder to which aluminum, bismuth, and indium are added in appropriate amounts. The performance was comparatively tested. The discharge capacity at room temperature was comparable to that of mercury-free alkaline batteries and mercury-containing alkaline batteries. However, comparing the discharge capacities at low temperature (-10 ° C, 10Ω continuous discharge, final voltage 0.9V), when the capacity of the mercury-containing alkaline battery was set to 100, that of the mercury-free alkaline battery was 56, which was very small. It was Moreover, the capacity at the time of high load discharge is considerably smaller than that of the mercury-containing alkaline battery. That is, converting the zinc powder into an amalgam has a great effect not only on improving the corrosion resistance of zinc but also on maintaining good discharge characteristics at low temperature and under high load.

The present invention has been made in view of the above-mentioned conventional problems, and an object thereof is to contain no trace amount of lead, indium, aluminum, gallium, tin, calcium, magnesium, bismuth, lithium, sodium and the like without containing mercury. Another object is to further improve the discharge characteristics of a mercury-free alkaline battery that uses the added zinc-based alloy powder as a negative electrode active material, and particularly to increase the capacity during low-temperature discharge and high-load discharge.

[0006]

In the present invention, therefore, attention has been paid to the particle size distribution of the zinc-based alloy powder. First, when the particle size distribution of the conventional zinc-based alloy powder for a mercury-free alkaline battery was measured, it was in the range of 75 to 450 μm, and only 80% or less of the powder having a small particle size of 300 μm or less was found. That is, 20% or more of powder having a large particle size of 300 μm or more was contained. On the other hand, with a zinc-based alloy powder having a particle size distribution of 75 to 450 μm, the proportion of powder having a small particle size of 300 μm or less was made larger than that of the conventional one, and an anhydrous silver alkaline battery was prototyped.
It was investigated how the discharge performance changes.

As a result, it is made of a zinc-based alloy which does not contain mercury and is added with a trace amount of one or more of lead, indium, aluminum, gallium, tin, calcium, magnesium, bismuth, lithium and sodium, and has a particle size distribution of 7.
When an alkaline battery is constructed by using, as a negative electrode active material, a powder having a small particle size of 5 to 450 μm and having a small particle size of 300 μm or less occupying 90% or more, good discharge characteristics are exhibited even at low temperature. I found it. That is, 300μ
In the present invention, the compounding ratio of the particle diameter of m or more was 20% or more, whereas in the present invention, it was 10% or less.

[0008]

[Function] The particle size distribution of the zinc-based alloy powder is 75 to 450 μm
Even if the range is the same as the above range, the compounding ratio of the large particle size of 300 μm or more is as large as 20% or more in the conventional one, whereas the compounding ratio of the large particle size of 300 μm or more is as small as 10% or less in the present invention. Therefore, the present invention has more fine particles than the conventional one. Therefore, the total surface area of the zinc-based alloy powder is increased, so that the reactivity in the electrolyte is improved, the reaction continues even at low temperature and under high load discharge, the utilization factor of the active material is improved, and the large discharge capacity is increased. Will be shown. 300μ
Since the zinc-based alloy powder with a large particle size of m or more has a smaller surface area per volume than the powder with a smaller particle size, the reactivity in the electrolytic solution is low and the active material during discharge at low temperature and high load is used. The usage rate of is very poor. By reducing the compounding ratio of such an undesirable powder having a large particle size of 300 μm or more, the utilization ratio of the active material is improved and the discharge capacity is increased.

[0009]

[Example] A trial manufacture of a mercury-free alkaline battery was carried out as follows.
Each discharge performance was comparatively evaluated. 4 aluminum
0 ppm, bismuth 150 ppm, indium 50
Using a zinc-based alloy containing 0 ppm and 10 ppm of lead as a raw material, a zinc-based alloy powder was manufactured by the atomization method. The particle size distribution is in the range of 75 to 450 μm, but this powder is appropriately classified and compounded, and the mixing ratio of the small particle size powder in the range of 75 to 300 μm is 75%, 80%, 90%. And four types of negative electrode materials were obtained. Using the four types of negative electrode materials as active materials, 100 LR6 alkaline batteries were manufactured with the same configuration except for the above.

For each prototype battery, -10 ° C, 1
A low-temperature discharge test under the conditions of 0Ω continuous discharge and a cutoff voltage of 0.9V and a high load discharge test under the conditions of 20 ° C., 2Ω continuous discharge and a cutoff voltage of 0.9V were performed. The average value for each was calculated. The results are shown in the graph below. In this graph, 7
It is shown as a relative value with the discharge capacity of a battery using a zinc-based alloy powder having a fine particle content in the range of 5 to 300 μm of 75% as 100. As you can see from this graph, 7
90% of the compounding ratio of the powder of the small particle size in the range of 5-300 μm
By increasing the amount above, good discharge characteristics were obtained.

[0011]

[Table 1]

[0012]

As described in detail above, according to the present invention, a zinc group which does not contain mercury and to which a trace amount of lead, indium, aluminum, gallium, tin, calcium, magnesium, bismuth, lithium, sodium or the like is added is added. It is possible to further improve the discharge characteristics of a mercury-free alkaline battery using alloy powder as a negative electrode active material, and particularly to increase the capacity during low temperature discharge and high load discharge.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kuniyoshi Nishida 5-36-11 Shinbashi, Minato-ku, Tokyo Fuji Electric Chemical Co., Ltd.

Claims (1)

[Claims] 1. Mercury-free lead, indium, aluminum, gallium, tin, calcium, magnesium,
What is claimed is: 1. An alkaline battery in which a powder of a zinc-based alloy to which a trace amount of one or more of bismuth, lithium, sodium and the like is added is used as a negative electrode active material, and the particle diameter of the zinc-based alloy powder is 75 to 45.
90 in the range of 0 μm and 300 μm or less
Alkaline battery characterized by occupying more than 100%.