JPH0287464A - Alkaline battery and negative electrode active substance thereof - Google Patents

Abstract

PURPOSE:To suppress generation of hydrogen gas while the Hg content is decreased to a great extent by adding a specified amount of polyoxyethylenesorbitane-aliphatic acid ester to an electrolyte consisting of alkali aque-solution or a neg. electrode active substance consisting of Zn alloy powder. CONSTITUTION:Existing invention includes Zn alloy powder, electrolyte, and a negative electrode material formed by adding 0.001-1.0 parts by weight polyoxyethylenesorbitane- aliphatic acid ester to 100 parts by weight Zn alloy powder. The Zn allow powder used as neg. electrode active substance shall contain a certain amount of at least one of the lead, aluminum, etc. Polyoxyethylenesorbitane-aliphatic acid ester is added to this neg. electrode material. For ex., Zn alloy powder is added into a solvent such as toluen, to which polyoxyethylenesorbitane-aliphatic acid ester is added, and upon mixing, the solvent is dried and volatilized to accomplish a coating layer of polyoxyethylenesorbitane-aliphatic acid ester over the surface of Zn alloy powder. Use of thus obtained substance to a neg. electrode active substance is the most favorable for suppressing generation of hydrogen gas and enhancing the discharging performance.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to an alkaline battery and its negative electrode active material, and more specifically, the present invention relates to an alkaline battery and its negative electrode active material. ) Formula (IIl [) is an ester bonded fatty acid represented by RCOOH, x, y, and z each represent an integer of 0 or more, and x, y, and z may be the same or different] 0.001 parts by weight of polyoxyethylene sorbitan fatty acid ester per 100 parts by weight of the zinc alloy powder.
The present invention relates to an alkaline battery and its negative electrode active material, in which the amount of hydrogen gas generated is significantly suppressed and the battery performance is improved by adding 1 part of -1.0mff.

[Prior Art] In an alkaline battery using zinc as a negative electrode active material, a strong alkaline electrolyte such as an aqueous potassium hydroxide solution is used, so the battery must be sealed tightly. This sealing of the battery is particularly important when attempting to miniaturize the battery, but it also traps hydrogen gas generated due to corrosion of zinc during battery storage. Therefore, during long-term storage, the gas pressure inside the battery increases, and the more completely the battery is sealed, the greater the risk of explosion.

As a countermeasure, research has been conducted to prevent the corrosion of zinc, which is an active material for the negative electrode, and to reduce the generation of hydrogen gas inside the battery. It is being done. For this reason, the negative electrode active materials of alkaline batteries commercially available today contain a large amount of mercury, about 3.0% by weight, and there is a social need to develop lower mercury or mercury-free batteries. It has become highly anticipated.

Therefore, various proposals have been made regarding zinc alloy powders in which various metals are added to zinc in order to reduce the mercury content in batteries. For example, there are zinc alloy powders in which lead is added to zinc, or zinc alloy powders in which lead and indium are added to zinc (Japanese Patent Application Laid-Open No. 181268/1983). Further, zinc alloy powders to which gallium, aluminum, etc. are added have also been proposed.

[Problems to be Solved by the Invention] By using zinc alloy powder in this way, it is certainly possible to suppress hydrogen gas generation even if the mercury content is reduced to a certain extent. The problem of deterioration in discharge performance accompanying a significant reduction in In other words, if the mercury content of zinc alloy powder is reduced to about 0.1 to 0.2% by weight in response to social needs, compared to the conventional mercury content of about 3.0% by weight. The hydrogen gas generation rate increases by about 4 to 5 times, and the discharge performance deteriorates to about 80%.

The following may be the cause of this.

That is, the following is considered to be the effect of mercury in the battery.

(1> Helps electrical contact between zinc alloy powder particles.

(2) It is effective in suppressing the formation of a passivation film on the surface of zinc alloy powder particles and uniformly dissolving zinc.

(3) Improve the corrosion resistance of zinc, and suppress electrical contact between zinc alloy powder particles from being inhibited by hydrogen gas bubbles generated as zinc corrodes.

However, when the mercury content of the zinc alloy powder becomes an extremely low mercury content of 0.2% by weight or less, the effect of mercury described in item (3) cannot be fully exerted. is considered to deteriorate.

In view of the current situation, it is an object of the present invention to provide an alkaline battery and its negative electrode active material in which the mercury content is significantly reduced, hydrogen gas generation is suppressed, and discharge performance is maintained at a high level. .

[Means for Solving the Problem] As a result of intensive research in line with this objective, the present inventors identified polyoxyethylene sorbitan fatty acid ester for use in negative electrode active materials made of zinc alloy powder or electrolytes made of alkaline aqueous solutions, etc. The present inventors have discovered that by adding a certain amount of polyoxyethylene sorbitan fatty acid ester, it is possible to obtain an alkaline battery in which hydrogen gas generation is significantly suppressed and discharge performance is improved compared to a battery without the addition of polyoxyethylene sorbitan fatty acid ester.

That is, the alkaline battery of the present invention includes □zinc alloy powder,
0 parts by weight of the zinc alloy powder.
．． The alkaline battery has a negative electrode material to which two parts of polyoxyethylene sorbitan fatty acid ester are added.

The present invention will be explained in more detail below.

In the present invention, the zinc alloy powder used as the negative electrode active material contains a certain amount of at least one of lead, aluminum, indium, magnesium, calcium, cadmium, tin, gallium, nickel, silver, etc. is exemplified. The method for producing this zinc alloy powder includes, for example, adding a predetermined amount of additional elements such as lead and aluminum to molten zinc, stirring to form an alloy, and then atomizing with compressed air to form a powder. The powder obtained by further sieving and sizing is used. The content of each additional element in this zinc alloy powder is 0
．． 0.001 to 0.5% by weight is common.

In the present invention, frozen zinc alloy powder obtained by further adding a desired amount of mercury during the production of the zinc alloy powder,
The above-mentioned zinc alloy powder is dry-blended with a desired amount of mercury using a V-type mill or a rotating drum, or the above-mentioned zinc alloy powder is mixed with a diluted solution such as potassium hydroxide or sodium hydroxide. Zinc alloy powder obtained by wet freezing with a desired amount of mercury in an alkaline solution may also be used, in which case the mercury content in the zinc alloy powder is lower than conventionally, i.e. 3.0 wt. % or less, and in consideration of low pollution, it is more preferably 1.5% by weight or less.

Further, the polyoxyethylene sorbitan fatty acid ester used in the present invention is a compound represented by the general formula (1). This compound is a polyoxyethylene sorbitan represented by the general formula (n) and the general formula (m
) A fatty acid represented by RCOOH is ester bonded, and x, y, and z each represent an integer of 0 or more, and x, y, and z may be the same or different. The preferable range of the carbon number of the fatty acid 1) in the present invention is 10 to
20, and specifically preferred ones include capric acid, undecylic acid, lauric acid, tridecylic acid, myristic acid, pentadecylic acid, valmitic acid, heptadecylic acid, stearic acid, nonadecanoic acid, arachidic acid, oleic acid, etc. Higher fatty acids are mentioned, and oleic acid is particularly preferred. The polyoxyethylene sorbitan fatty acid ester used in the present invention may be any one of the polyoxyethylene sorbitan fatty acid esters represented by the general formula (1), or two types of polyoxyethylene sorbitan fatty acid esters.
It may be a mixture of more than one species.

In the alkaline battery of the present invention, in the negative electrode material containing the zinc alloy powder and an electrolyte such as an aqueous potassium hydroxide solution,
Add the polyoxyethylene sorbitan fatty acid ester described above. The method of addition is to coat zinc alloy powder with polyoxyethylene sorbitan fatty acid ester,
Examples include a method of using this as a negative electrode active material, or adding it to an electrolytic solution such as an aqueous potassium hydroxide solution or an aqueous sodium hydroxide solution or a gelling agent, but in the present invention, polyoxyethylene sorbitan fatty acid ester After mixing the zinc alloy powder in a solvent such as toluene that has been added with It is most preferable to use it from the viewpoint of suppressing hydrogen gas generation and improving discharge performance.

In addition, in the present invention, the zinc alloy powder on which the coating layer of polyoxyethylene sorbitan fatty acid ester is formed on the surface is frozen by the same method as the method for freezing the zinc alloy powder described above, A coating layer containing a mixture of polyoxyethylene sorbitan fatty acid ester and mercury may be formed on the surface of the zinc alloy powder.

Further, mercury may be added and mixed into the electrolytic solution forming the negative electrode material together with the zinc alloy powder on which the coating layer of polyoxyethylene sorbitan fatty acid ester is formed on the surface.

Here, the amount of polyoxyethylene sorbitan fatty acid ester added to the negative electrode material is 100% of the above zinc alloy powder.
The amount is 0.001 to 1.0 parts by weight. Added amount of polyoxyethylene sorbitan fatty acid ester is 0
．． If it is less than 0.001 parts by weight, the effects of the present invention, such as improving the corrosion resistance of zinc and preventing hydrogen gas generation, cannot be obtained;
．． If the amount exceeds 0 parts by weight, during discharge, the polyoxyethylene sorbitan fatty acid ester present in the electrolyte, etc. in the coating layer of polyoxyethylene sorbitan fatty acid ester formed on the surface of the zinc alloy powder acts as a barrier, and the zinc Good discharge performance cannot be obtained because the dissolution reaction is inhibited.

Although the effects of these polyoxyethylene sorbitan fatty acid esters have not been fully elucidated, it is presumed that during storage of the battery, polyoxyethylene sorbitan fatty acid esters adsorb to the surface of zinc alloy powder and act as an inhibitor. It is effective in improving the corrosion resistance of zinc alloy powder, suppresses the generation of hydrogen gas that accompanies corrosion of zinc, and also eliminates the negative effects of inhibiting electrical contact between zinc alloy powder particles due to hydrogen gas bubbles that were previously observed during discharge. It is thought that the discharge performance is improved by suppressing the discharge.

[Examples] The present invention will be specifically described below based on Examples and Comparative Examples.

Examples 1 to 5 and Comparative Examples 1 to 3 Zinc alloys were created by melting zinc ingots with a purity of 99.997% or higher at about 500°C and adding each element shown in Table 1, excluding mercury. This is then heated with high pressure argon gas (ejection pressure 5
Kg/crA). This powder is 5
Zinc alloy powder was obtained by sieving to a particle size range of 0 to 150 mesh.

Next, mercury was added to the above powder in an alkaline solution of 10% potassium hydroxide so that the content ratio shown in Table 1 was obtained, and the hydrated zinc alloy/powder shown in Table 1 was subjected to freezing treatment. I got it.

Next, polyoxyethylene sorbitan fatty acid ester (
Manufactured by NOF■, product 82 Nonion 0T-221, composition:
The above glazed zinc alloy powder was added to the toluene solvent in which polyoxyethylene sorbitan monooleate (polyoxyethylene sorbitan monooleate) was added and dissolved, and the toluene was dried and volatilized while mixing, and the surface of the glazed zinc alloy powder was coated with the powder shown in Table 1. A coating layer of polyoxyethylene sorbitan fatty acid ester in the proportion shown was formed to form a negative electrode active material.

Further, an electrolytic solution was prepared by adding carboxymethyl cellulose and sodium polyacrylate as a gelling agent to a 40% potassium hydroxide aqueous solution saturated with zinc oxide at about 1.theta.%.

Negative electrode active material obtained above 3. Og and electrolyte 1.8
A negative electrode material was prepared by mixing g and forming a gel. Also,
A positive electrode material was prepared by mixing manganese dioxide and a conductive agent. Using these negative electrode materials and positive electrode materials, an alkaline manganese battery shown in FIG. 1 was prepared and tested.

The alkaline manganese battery shown in Figure 1 consists of a positive electrode can 1, a positive electrode 2,
Negative electrode (gelled frozen zinc alloy powder) 3, separator 4, sealing body 5, negative electrode bottom plate 6, negative electrode current collector 7, cap 8, heat-shrinkable resin tube 9, insulating ring 10, 11 outer can 12 It is configured.

Using this alkaline manganese battery, the discharge load is 2Ω, 20
The discharge duration up to a final voltage of 0.9 V was measured under the discharge conditions of 0.0C and expressed as an index with the measured value of Comparative Example 1 using a conventional negative electrode material not containing polyoxyethylene sorbitan fatty acid ester as 100. The results are shown in Table 1.

In addition, the gas generation rate (d/g-day) was measured for 20 days at 60°C using the above negative electrode material, and the results were compared to Comparative Example 1 using a conventional negative electrode material that does not contain polyoxyethylene sorbitan fatty acid ester. It is also listed in Table 1 as an index with the constant value of 7TIJ as 1.0.

Example 6 Polyoxyethylene sorbitan fatty acid ester (manufactured by NOF ■) was applied to the surface of the same unfrozen zinc alloy powder as in Example 2 in the same manner as in Example 2 without being subjected to ice treatment. Name: Nonion 0T-22L Composition: Polyoxyethylene sorbitan monooleate) was used to form a coating layer of polyoxyethylene sorbitan fatty acid in the proportion shown in Table 1.
The discharge duration and gas generation rate were determined in the same manner as in Example 2, except that the negative electrode active material was obtained by applying ice treatment to the ratio shown in Table 1 in the same manner as in Example 2. ΔIIJ was determined and the results are also listed in Table 1.

Example 7 Polyoxyethylene sorbitan fatty acid ester (manufactured by Nippon Oil & Fats Corporation, commercial product Name: Nonion 0T-221, Composition: Polyoxyethylene sorbitan monooleate) was used to form a coating layer of polyoxyethylene sorbitan fatty acid ester in the proportions shown in Table 1. The discharge duration and gas generation were determined in the same manner as in Example 2, except that 3.0 mg of mercury was added to 1.8 g of the same electrolyte as in Example 2, mixed to form a gel, and used as the negative electrode material. Perform the n1 constant of the ratio and apply each result to the first
Also listed in the table.

Example 8 To 1.8 g of the same electrolyte as in Example 2, 3.0 g of the same frozen zinc alloy powder as in Example 2 and polyoxyethylene sorbitan fatty acid ester (manufactured by NOF ■, product 82) were added. 3. Nonion 0T-221, composition: polyoxyethylene sorbitan monooleate). The discharge duration and gas generation rate were measured in the same manner as in Example 2, except that On+g was added and mixed to form a gel, and the negative electrode material was used. The results are also listed in Table 1.

As shown in Table 1, Example 1 using a negative electrode material in which the negative electrode active material was a glazed zinc alloy powder coated with polyoxyethylene sorbitan fatty acid ester containing 0.1% by weight of mercury. -4 shows that compared to Comparative Examples 1 and 2 in which polyoxyethylene sorbitan fatty acid ester was not added to the negative electrode material, the hydrogen gas generation rate was lower regardless of the difference in the composition of the glazed zinc alloy powder that is the negative electrode active material. Moreover, alkaline batteries incorporating this negative electrode material had excellent discharge performance.

In addition, Example 5 used a negative electrode material in which the negative electrode active material was a frozen zinc alloy powder with a mercury content of 1.0% by weight coated with polyoxyethylene sorbitan fatty acid ester. In this case as well, compared to Comparative Example 3 in which polyoxyethylene sorbitan fatty acid ester was not added to the negative electrode material, the discharge performance of the alkaline battery incorporating this negative electrode material was improved and the hydrogen gas generation rate was significantly reduced.

Furthermore, Example 6 used a negative electrode material in which the surface of unhydrated zinc alloy powder was coated with polyoxyethylene sorbitan fatty acid ester and then subjected to a hydration treatment. In this case, the hydrogen gas generation rate was significantly reduced, and alkaline batteries incorporating this negative electrode material had excellent discharge performance.

Example 7 uses polyoxyethylene sorbitan fatty acid ester coated on the surface of unfrozen zinc alloy powder as the negative electrode active material, and uses a negative electrode material obtained by adding and mixing together with mercury into the electrolyte. However, even in this case, the hydrogen gas generation rate was significantly reduced and the discharge performance of the alkaline battery incorporating this negative electrode material was significantly improved.

Example 8 uses a negative electrode material in which a predetermined amount of polyoxyethylene sorbitan fatty acid ester is added and mixed into an alkaline aqueous solution as an electrolytic solution, but this also has the effect of suppressing hydrogen gas generation. Moreover, it was also effective in improving the discharge performance of alkaline batteries incorporating this negative electrode material.

[Effects of the Invention] As explained above, according to the alkaline battery of the present invention having a negative electrode material to which a specific amount of polyoxyethylene sorbitan fatty acid ester is added, when the mercury content is lowered than before, the mercury Even when using an ultra-low mercury content of 0.2% by weight or less of the zinc alloy powder used, hydrogen gas generation within the battery is significantly suppressed.
Moreover, battery performance is improved. Furthermore, since the mercury content can be lowered than before, it also meets social needs. In particular, the effect is even more remarkable by using a negative electrode active material in which zinc alloy powder is coated with a specific amount of polyoxyethylene sorbitan fatty acid ester.

[Brief explanation of the drawing]

FIG. 1 shows a side sectional view of an alkaline manganese battery according to the present invention. 1: positive electrode can, 2: 4: separator 6 two negative electrode bottom plates, 8: cap 1 positive electrode, 3: negative electrode, 5: sealing body, 7: negative electrode current collector, 9: heat-shrinkable resin tube, 10, 11: Insulation ring, 12: Exterior can. Patent applicant Mitsui Metal Mining Co., Ltd.

Claims (1)

[Claims] 1. Zinc alloy powder and electrolyte, the zinc alloy powder 10
An alkaline battery having a negative electrode material to which 0.001 to 1.0 parts by weight of polyoxyethylene sorbitan fatty acid ester is added. 2. 0.001 to 1 per 100 parts by weight of zinc alloy powder
．． A negative electrode active material for an alkaline battery, comprising 0 parts by weight of polyoxyethylene sorbitan fatty acid ester coated on the surface of the zinc alloy powder.