JPS6196665A - Zinc alkaline primary battery - Google Patents

Abstract

PURPOSE:To obtain a zinc alkaline primary battery whose discharge performance and storage life are improved by using a low amalgamated corrosion resistant zinc alloy as a negative electrode and mixing a specified conductive material thereto. CONSTITUTION:Corrosion resistant zinc alloy powder having an amalgamation ratio of 2wt% or less is mixed to a conductive material comprising a metal or alloy which is powder, fiber, or flake, and is easy to be amalgamated, and has the alkali resistant surface and noble potential than zinc, to form a negative electrode. At least the surface of the conductive material consists of silver, thallium, gallium, indium, tin, lead, copper, gold, or an alloy mainly comprising these metals, such as brass. When a nonconductive material is used, the conductive surface is formed by applying chemical plating to the material, or electro- plating on the chemical plating.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is an improvement of a zinc-alkaline primary battery using zinc as a negative electrode active material, an alkaline aqueous solution as an electrolyte, and silver manganese dioxide oxide, mercury oxide, oxygen, etc. as a positive electrode active material. It is related to.

A common problem with conventional zinc-alkaline primary batteries is corrosion of the zinc negative electrode by the electrolyte during storage. Conventionally, i
[It has been adopted as an industrial method to increase the hydrogen overvoltage by using zinc chloride powder containing 4 to 10 parts of mercury to lead and to suppress corrosion to a level that poses no practical problems. There is. 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.
Various studies have been conducted. For example, methods have been proposed to improve corrosion resistance and reduce the rate of corrosion using alloy powders in which lead, gallium, indium, etc. are added to zinc, or powders in which zinc is coated with these elements. Although this method 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 the rate is lowered is unclear, but due to the lack of mercury, the diffusion-dominated electrochemical reactivity between the zinc surface and the electrolyte decreases. In addition to this, the main cause is thought to be insufficient electronic conductivity between the zinc particles of the negative electrode and between the zinc particles and the current collector.

There are still no proposals to solve the above-mentioned problems, and there are some related technologies that are seemingly similar to the content of the present invention described below, but they all have fundamentally different objectives 1 and effects. , does not solve this problem. Specifically, as one of the techniques for downsizing button-type alkaline batteries, it has been proposed to use a negative electrode made of a mixture of zinc hydrate powder and easily viscous metal powder. No. 147363)
. However, this proposal uses ordinary zinc for a powder negative electrode containing all mercury at a marketable rate of 5 to 25% by weight, improving weighing accuracy, uniformity of filling of the negative electrode, and making the current collecting surface of the negative electrode less cloudy. The purpose of this is to speed up the process, and for that purpose, a large amount of easily viscous metal powder with a viscosity rate of 5 to 25% by weight is used, which is 50 to 100% of the viscosity of zinc. Therefore, in order to satisfy the corrosion resistance and discharge performance of 9+ at a low water conversion rate, which is the objective of the present invention,
This proposal cannot be applied because it is based on the assumption that a large amount of mercury will be used.

Furthermore, as a related technology, I would like to add that in the technical field of secondary batteries, gold and silver are used in zinc chloride negative electrodes.

A method has been proposed to improve the charging and discharging properties of zinc negative electrodes by adding metals with high hydrogen overvoltage, such as tin (
% Kosho No. 45-6733).

In the above proposal, the action of the additive metal is to capture the mercury as a total amalgam released from zinc chloride during discharge, suppress the coarsening of mercury grains, reduce and stabilize the electrical resistance, and reduce the charging The main focus is to ensure the absolute amount of zinc precipitation nuclei and uniformly deposit zinc during the process, and is an improvement that is useful only in secondary batteries, especially when the zinc negative electrode contains a relatively large amount of mercury. It's technology.

In addition, with the zinc negative electrode with a relatively high oxidation rate of 4% by weight as disclosed in the above proposal, corrosion resistance and discharge performance of 5 strong can be obtained without any problems, and almost enough mercury can be deposited on the zinc negative electrode as a primary battery. It is determined empirically that

Problems to be Solved by the Invention The zinc negative electrode of the primary battery that is the subject of improvement in the present invention has a hydration rate of about 2% by weight or less, and the amount of mercury is insufficient to ensure corrosion resistance and discharge performance of 9 strong. It is. Therefore, in addition to using a special corrosion-resistant alloy for the negative electrode, it is necessary to establish all new means that can supplement or replace the function of mercury in order to ensure strong discharge performance. In the case of such a low rate of reduction, when zinc hydroxide and zinc oxide are deposited as insoluble substances on the surface of the zinc particles due to the discharge reaction, the mercury does not easily separate from the zinc particles because the amount of mercury contained in the zinc particles is small. Otherwise, the fine granular mercury that should be interposed between the particles and serve as a medium for electronic conduction is insufficient, increasing the internal resistance and deteriorating the strong discharge performance. Therefore, the present invention combines the above-mentioned proposal as a related art, and achieves the following objectives:
However, since the proposed method is applied in a different technical field to a primary battery, it would have little effect. As described above, it is an object of the present invention to establish a technology for a zinc negative electrode with a low hydration rate that combines corrosion resistance and strong discharge performance, and to realize a complete low-pollution zinc-alkaline primary battery.

Means to Solve the Problems The present invention uses an alkaline aqueous solution containing caustic potash, caustic soda, etc. as its main components as an electrolyte, zinc as a negative electrode active material, and manganese dioxide, silver oxide, mercury oxide, or mercury oxide as a positive electrode active material. In so-called zinc-alkaline primary batteries that use oxygen, etc., the main component is a corrosion-resistant zinc alloy powder containing at least indium and having an agglomeration rate of 2% by weight or less, which is granular, fibrous, or scaly and has at least an alkali-resistant surface. It is characterized by the use of a negative electrode mixed with a conductive material made of a metal or alloy that is easily oxidized and nobler than zinc. More specifically, the material of at least the surface layer of the conductive material is silver, thallium, gallium, indium, tin, lead, copper, gold, or an alloy containing these as main components, such as brass. In addition, in addition to cases where the conductive material is composed not only of the surface but also of the above-mentioned substances, there are also cases where the center is made of a solid substance that is resistant to deterioration, and the surface layer is coated with the above-mentioned substances. You can take it. for example,
Materials for the core include polyethylene, polypropylene, nylon, polyester, acrylic resin, polystyrene resin, fluorine resin, alkali-resistant resins such as cellulose and its derivatives, alkali-resistant ceramics such as alumina, and non-conductive materials such as glass. good. Furthermore, as conductive substances, carbon and alkali-resistant resins using carbon as a conductive filler are used, and as metals, metals that can be modeled and are more noble than zinc, such as nickel, stainless steel, or alloys mainly composed of nickel, are used. be able to.

It is possible to form a surface layer of the above-mentioned easily phosphorizable metal on the particles, short fibers, or scales of the material at the center of the kohachi to make it a conductive material. If the part is made of a non-conductive material, a surface layer may be formed by, for example, chemical plating or electroplating on the chemical plating layer.

Further, when the center portion is made of a conductive material, the surface layer can be formed by electroplating alone in addition to the above.

The corrosion-resistant zinc alloy powder used in the present invention may be obtained by adding additive elements such as indium to molten zinc in a nearly uniform distribution and then pulverizing it by an injection method, or pure zinc powder. Alternatively, the same effect can be obtained by applying an additive element to the surface of zinc alloy powder by displacement plating or vapor deposition, or by incorporating it into mercury at the time of oxidation.

Function The reason why an alloy containing indium is used as the corrosion-resistant zinc alloy powder in the present invention is that it is the most practical to ensure sufficient corrosion resistance as a negative electrode for zinc-alkaline primary batteries with a low hydration rate of 2% by weight or less. It's for a reason. In other words, indium is the most effective alloy additive element for increasing the corrosion resistance of zinc compared to other additive elements such as lead, thallium, cadmium, and gallium, and without the addition of indium, a zinc alloy can be obtained that is the decisive factor in corrosion resistance. That is difficult. Of course, by adding indium in an appropriate combination with each of the above elements, aluminum, carnoum, etc., a zinc alloy with better corrosion resistance can be obtained than with an alloy simply adding indium, and these corrosion-resistant zinc alloy powders One important requirement of the present invention is to use .

As mentioned above, in addition to ensuring the corrosion resistance of the zinc negative electrode with a low hydration rate of 2% by weight or less, it is also necessary to satisfy strong discharge performance, and an effective means for achieving this is to mix the above-mentioned conductive material in the negative electrode. Another important requirement of the present invention is to make it possible. As mentioned above, as a result of the discharge reaction of the zinc negative electrode, discharge products accumulate on the surface of the zinc particles and electrical conductivity between the particles worsens, but this problem has conventionally been solved by reducing the hydration rate to about 4 to 10% by weight. The problem has been solved by incorporating mercury into zinc and interposing fine granular mercury, which is liberated from the surface layer of the zinc particles upon discharge, between the zinc particles to ensure electronic conduction. However, in the case of a low porosity of 2% by weight or less, most of the mercury contained in the surface layer of the zinc particles consumed by discharge diffuses into the interior of the zinc particles, and becomes a medium for conduction between the zinc particles. There is almost no release of fine particulate mercury, which can become mercury. As a result, the electronic conductivity of the negative electrode active material becomes insufficient, and the strong discharge performance deteriorates. One of the roles of the conductive material used in the present invention is to completely complement or replace the above-mentioned effects of free mercury, and for this purpose, a conductive material that satisfies all of the following conditions is used. In other words, it has good alkali resistance and conductivity, does not discharge preferentially to zinc, and is not consumed in the final discharge stage 1, and has a high hydrogen overvoltage or is easily hydrated and has a high hydrogen overvoltage in the hydrated state. It is necessary that zinc not be corroded by local action, and furthermore, that it be in a shape that can serve as a medium for contact between each particle when mixed in zinc particles.

More preferably, a high concentration of mercury is supported on the surface layer of the conductive material, and no mercury is present in the center, so that only the surface layer is allowed to perform its substantial function by simply turning the conductive material into a liquid with a small amount of mercury. Using a conductive material coated with an easily oxidized metal is effective for reducing pollution.

The conductive materials listed above satisfy these conditions, and the effects of the present invention using these materials will be further explained. When an electrolyte comes into contact with a pressure-molded negative electrode in which a corrosion-resistant low-hydration zinc alloy powder and a fully conductive material are mixed in contact with each other, or a gel-like negative electrode, mercury is gradually released from the zinc alloy powder. It diffuses and the surface layer of the conductive material becomes transparent.

Therefore,! During or immediately after battery construction, the above hydration progresses to form a state in which there is no local corrosion between the conductive material and the zinc alloy powder, ensuring corrosion resistance of the negative electrode during battery storage. In order to more reliably form this state free of local corrosion, it is best to make the surface of the conductive material t=p- in advance and then mix it with the low-corrosion zinc alloy powder to form a battery.
This method is especially necessary when a zinc alloy powder with a hydration rate of zero or a hydration rate close to this is used as the negative electrode active material.

Next, when the battery is fully discharged, reaction products with high electrical resistance are gradually deposited on the surface of the zinc alloy powder, and as a result, the apparent volume of the negative electrode increases significantly, and under the compression force, the zinc alloy powder A conductive material interposed between the powder particles is partially press-fitted into the deposited layer and remains in contact with the unreacted portions of the zinc alloy powder. As a result, electrical continuity between the active surfaces of each zinc alloy powder is reliably maintained from the early stage to the final stage of discharge, without being hindered by the above-mentioned high-resistance deposited layer. The function previously performed by fine particles of free mercury can be supplemented or replaced by a conductive material. In this way, even with a low mercury content, it is possible to substantially expand the reaction surface area during discharge, and the increase in internal resistance is also suppressed, resulting in a battery with high discharge voltage and large capacity, especially at high current densities. can get. In addition, the role of the conductive material is to maintain electrical continuity between the negative electrode current collector and the zinc alloy powder in addition to the function as a conductive medium between the zinc alloy powders, and the conductive material fulfills both roles. As a result, the characteristics of the negative electrode are comprehensively improved.

In other words, in the case of the conventional zinc negative electrode, which has a relatively high conversion rate,
Mercury liberated during discharge acts as a medium for conduction with the current collector, but in the case of the present invention, as an alternative medium, the conductive material present near the current collector is a zinc alloy in the vicinity. Complete electrical continuity between the powder and the surface of the current collector. The function can be understood by thinking in the same way as the case between zinc alloys described above, so a complete explanation will be omitted. As described above, the present invention has realized a zinc-alkaline primary battery that has both discharge performance and storability by using a corrosion-resistant zinc alloy with a low wood reduction rate for the negative electrode and mixing it with the conductive material described in detail in the text. This will be explained in detail below using examples.

EXAMPLE FIG. 1 is a sectional view of a cylindrical alkaline manganese battery used in an experiment to confirm the effects of the present invention, and FIG. 2 is an enlarged view of the main parts. 1st. In Fig. 2, numeral 1 is a positive electrode case made of iron with nickel agate, inside of which is a positive electrode 2 made of a mixture of graphite and manganese dioxide and pressure molded, a separator 3 made of polypropylene non-woven fabric, a bottom plate 4 made of cellulose, and a bottom plate made of carboxymethyl cellulose. A gel-like negative electrode 7 is housed in which various kinds of non-oxidized or non-oxidized zinc alloy powders 5 and various conductive materials 6 are mixed and dispersed in an electrolyte of a gelled caustic potassium aqueous solution. There is. FIG. 2 is an enlarged view of a part 7' of the negative electrode when granular conductive material 6 is used. 8 is a sealing plate made of polypropylene that seals the opening of the case 1, and a negative electrode current collector 9 made of brass is placed in the center.
is fixed.

10 is a negative terminal plate, 1111″i is a positive terminal plate, 12.1
3 is an insulating ring, 14 is a heat-shrinkable resin tube, and 16 is a metal exterior can. The prototype batteries were AA-sized alkaline manganese batteries; among the batteries prototyped at the same time as comparative examples, there were batteries that did not use conductive material 6 for the negative electrode, and batteries that did not use conductive material 6 for the negative electrode.
Although there is a battery using powder of high purity zinc (more than 99,997) in place of the battery, the structure of the battery is basically the same as that shown in FIG. The particle size of both zinc alloy powder and pure zinc powder is 5.
These powders, ranging from 0 to 150 Metsutsuyu, were made in the following manner. That is, various zinc alloys are prepared by adding all the elements listed in Table 1 to zinc ingots with a purity of 99. and sieved to the above particle size range.
If the above powder requires oxidation, use 1 part of caustic potash.
The above powder was put into a 0% by weight aqueous solution, and while stirring, a predetermined amount of mercury was added dropwise to form a solution. Thereafter, it was washed with water, substituted with acetone, and dried to produce a zinc oxide powder or a zinc oxide alloy powder. For the conductive material, copper or silver powder of 100 to 300 meters, or glass powder of 100 to 300 meters is electrolessly plated with copper to a thickness of 1 to 300 meters.
Electroless plating is applied to the surface of graphite fibers with a fiber diameter of 6 to 20 μ and a length of 2 to 5 UIL to a thickness of 0.
．． The one to which 5 to 1 μm of copper was attached was used. In addition, if the conductive material is to be pre-condensed before constructing the battery, copper powder or copper-attached graphite fibers are added to a dilute hydrochloric acid solution containing dissolved water, stirred, and washed with water.

After drying, the copper was converted into water. The amount of mercury in the conductive material was 4% by weight relative to copper in the case of copper powder, and 2% by weight in the case of graphite fibers attached with tuning.

Table 1 shows the details of the AA alkaline manganese batteries prototyped using these materials. The weight of zinc in the negative electrode of each battery was 2.6f, and the weight of the conductive material was unified to 4% (0.1y-) relative to zinc by weight before b- conversion.

Further, the oxidation rate was expressed as the ratio of the weight of mercury to the weight of zinc, and the content of added elements in the zinc alloy was expressed as weight % with respect to the weight of the zinc alloy.

Below are the margins, and as shown in Table 1, each of the prototype batteries was tested at 45°C.
After storage for one month, the continuous discharge performance of 1 QΩ and the degree of expansion of the battery were evaluated at 20'C.

Table 2 shows the evaluation results for -t.

Table 2 As shown in Tables 1 and 2, among the comparative examples listed below, the case where corrosion-resistant zinc containing indium was not used and the reduction rate was as low as 2% (Comparative Example 1゜3 ) has extremely poor discharge performance despite using a conductive material. This is because the corrosion resistance of the negative electrode is poor, as can be seen from the fact that the total height change (expansion) of the battery is larger than that of other batteries, and a large amount of hydrogen gas is generated due to the corrosion reaction of zinc. It is thought that the EL discharge reaction is inhibited by the presence of the metal and by the deformation caused by the increase in internal pressure, which causes poor contact. In addition, Comparative Example 2 had a high conversion rate of 4,
The corrosion resistance of the negative electrode is almost sufficient, and the discharge performance is comparable to that of the examples, but the disadvantage is that a large amount of mercury, 100111 g, is required per battery.

Furthermore, since Comparative Example 4 uses a corrosion-resistant alloy containing indium, the corrosion resistance is sufficient at a oxidation rate of 2. However, as the discharge reaction progresses, the reaction resistance of the negative electrode increases, resulting in unsatisfactory discharge performance. I can't get it. The disadvantages of these comparative examples are
All of the examples show improved characteristics. That is, the use of a corrosion-resistant zinc alloy containing indium is the lowest point. Corrosion resistance is ensured at a low corrosion rate, and excellent discharge performance can be obtained due to the action of the conductive material. Among these, cases in which the easily-fading metal is attached only to the surface of the conductive material (Examples 1 to 3) and cases in which the conductive material is composed only of the easily-fading metal (Examples 8 to 9) When compared using the same amount of mercury, the corrosion resistance effect and the improvement effect on discharge performance are particularly large. Of course, among the examples, those with relatively soft properties and a high hydration rate are good, but even if the hydration rate is less than 0.5 inch, the conductive material may be hydrated using a small amount of mercury in advance. It has been shown that sufficient performance can be obtained for practical use if used in the same way.

Effects of the Invention As described above, according to the present invention, a zinc-alkaline primary battery with low pollution and excellent performance can be obtained by reducing the filtration rate of negative electrode zinc.

[Brief explanation of the drawing]

FIG. 1 is a partially cross-sectional side view of a cylindrical alkaline manganese battery used in an example of the present invention, and FIG. 2 is an enlarged view of all essential parts of the same negative electrode. 2゛°...Positive electrode, 3...Separator, 5...
... Corrosion-resistant zinc alloy powder, 6 ... Conductive material, Completed.
...Gel-like negative electrode. Name of agent: Patent attorney Toshio Nakao and 1 other person
1 Figure 2 Figure 5--1 Corrosion resistant material 6, -111 Conductive material

Claims (9)

[Claims] (1) Mainly consists of corrosion-resistant zinc alloy powder that has been bleached with 2% by weight or less of mercury or has not been bleached, and that has a granular, fibrous or scaly shape with at least the surface being alkali-resistant and easy-graining. A zinc-alkaline primary battery that has a zinc negative electrode mixed with a conductive material made of a metal or alloy nobler than zinc. (2) The zinc-alkaline primary battery according to claim 1, wherein the corrosion-resistant zinc alloy contains at least indium. (3) At least the surface of the conductive material is copper, silver, tin, thallium,
The zinc-alkaline primary battery according to claim 1 or 2, which is composed of one or more selected from the group consisting of gallium, indium, lead, gold, or alloys containing these as main components. (4) The zinc-alkaline primary battery according to claim 3, in which the central portion of the conductive material is made of a solid material that is resistant to deterioration. (5) The zinc-alkaline primary battery according to claim 4, wherein the center of the conductive material is glass. (6) The zinc-alkaline primary battery according to claim 4, wherein the center portion of the conductive material is made of alkali-resistant plastic. (7) The zinc-alkaline primary battery according to claim 4, wherein the center of the conductive material is made of carbon or a conductive, alkali-resistant plastic containing carbon as a conductive filler. (8) The zinc-alkaline primary battery according to claim 4, wherein the central portion of the conductive material is made of a metal or alloy that is resistant to weathering and is nobler than zinc and resistant to alkali. (9) The zinc-alkaline primary battery according to any one of claims 1 to 8, wherein at least the surface of the conductive material is coated before battery construction.