JPH07161356A - Alkaline battery - Google Patents

Abstract

PURPOSE:To improve discharge characteristics of non-amalgamated alkaline battery using zinc alloy powder as a negative pole active material by setting in a specified range, bulk density of zinc alloy powder, in which no mercury is contained but small amount of more than one of specified alloy elements are added. CONSTITUTION:An alkaline battery which is composed of zinc alloy, in which small amounts of more than one kind of lead, indium, alminium, gallium, tin, calcium, magnesium, bismuth, lithium, sodium, etc., are added but no mercury is contained, and formed by using the powder within the range of bulk density of 2.2-2.6g/cm<3> as a negative electrode active material, expresses favorable discharge characteristic ever under a low temperature. Zinc alloy power having small bulk density has a large surface area per volume. Therefore reactivity in electrolyte is improved, reactivity continues even if discharging under a low temperature, utilization rate of active material is improved, and large discharge capacity is exhibited.

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 400 .mu.m, most of which have a potato-like particle shape (relatively. Round potatoes and elongated sweet potatoes are usually mixed). 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 to improve 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, with regard to lead, there is a concern of environmental pollution problems, so there is a tendency to use it as little as possible). A large amount of data has been accumulated regarding the appropriate addition amount of these alloy elements and the combined addition of a plurality of elements, and 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 significantly lower than that at normal temperature. 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 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 temperatures.

The present invention has been made in view of the above-mentioned conventional problems, and does not contain mercury and contains lead, indium, aluminum, gallium, tin, calcium, magnesium,
The object is to further improve the discharge characteristics of a mercury-free alkaline battery using a zinc-based alloy powder to which a small amount of bismuth, lithium, sodium, etc. is added as a negative electrode active material, and particularly to increase the capacity during low-temperature discharge.

[0006]

Therefore, in the present invention, attention is paid to the apparent density of the zinc-based alloy powder. First JIS
-According to the apparent density test method specified in Z-2504,
When the apparent density of the conventional zinc-based alloy powder for a mercury-free alkaline battery was measured, it was in the range of 2.7 to 4.0 g / cm. On the other hand, various conditions for producing the zinc-based alloy powder by the atomization method were changed to produce various powders with an apparent density of 2.8 g / cm ³ or less, and alkaline batteries using these zinc-based alloy powders were manufactured. It was manufactured in the same manner as the conventional one, and its discharge performance was examined.

As a result, mercury-free zinc-based alloys containing trace amounts of one or more of lead, indium, aluminum, gallium, tin, calcium, magnesium, bismuth, lithium, sodium, etc., have an apparent density of 2 It has been found that when an alkaline battery is constructed by using a powder in the range of 0.2 to 2.6 g / cm ³ as a negative electrode active material, good discharge characteristics are exhibited even at low temperatures.

[0008]

The apparent density of the metal powder is a numerical value related to the particle shape, and the larger the surface area per volume, the smaller the apparent density. The zinc-based alloy powder having an apparent density of 2.2 to 2.6 g / cm ³ which is smaller than the conventional one has a larger surface area than the conventional one. Therefore, it is considered that the reactivity in the electrolytic solution is improved, the reaction is continued even at the discharge at a low temperature, the utilization factor of the active material is improved, and a large discharge capacity is exhibited. When the zinc powder was produced by the atomization method, the apparent density had a lower limit of about 2.1 g / cm ^{3 due} to production characteristics.

[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
Six kinds of zinc-based alloy powders having different apparent densities were manufactured by using a zinc-based alloy with 0 ppm and 10 ppm of lead added as a raw material (the particle size distribution is in the range of 75 to 450 μm and in the range of 75 to 300 μm). Is common to 6 species). In this way, six types of zinc-based alloy powders having different apparent densities are used as negative electrode active materials,
Others have the same structure and each one LR6 type alkaline battery
I made 00 pieces.

For each prototype battery, -10 ° C, 1
A low temperature discharge test was carried out under the conditions of 0Ω continuous discharge and a final voltage of 0.9 V, the discharge capacity was measured, and an average value of 100 pieces of each of 6 types was obtained. The results are shown in the graph below.
In this graph, the relative density is shown with the discharge capacity of the battery using the zinc-based alloy powder having an apparent density of 2.8 g / cm ³ as 100. As you can see from this graph,
A battery using a zinc-based alloy having an apparent density in the range of 2.2 to 2.6 g / cm ³ showed good characteristics.

[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. The discharge characteristics of a mercury-free alkaline battery using the alloy powder as a negative electrode active material can be further improved, and in particular, the capacity at low temperature discharge can be increased.

 ─────────────────────────────────────────────────── ─── 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 apparent density of the zinc-based alloy powder is 2.2.
Alkaline battery characterized by being in the range of up to 2.6 g / cm ³ .