JPH0337961A - Alkaline battery and its negative active material - Google Patents

Abstract

PURPOSE:To retard hydrogen gas evolution for a long time even if the content of mercury is remarkably reduced and furthermore to keep discharge performance high for a long time by using a negative electrode material containing a silane coupling agent and a surface active agent in addition to zinc alloy powder and an electrolyte. CONSTITUTION:A negative electrode material contains a silane coupling agent and a surface active material in addition to zinc alloy powder and an electrolyte. The contents of the silane coupling agent and the surface active agent are preferably 0.001-1.0 pts.wt. each based on 100 pts.wt. zinc alloy powder. Even if the content of mercury is reduced to a lower level such as 0.2wt% or less based on the weight of the zinc alloy powder, hydrogen gas evolution is remarkably retarded and discharge performance is increased and kept high for a long time.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to alkaline batteries and their negative electrode active materials. Specifically, the present invention relates to alkaline batteries and their negative electrode active materials. By adding a surfactant and a surfactant, the amount of hydrogen gas generated is significantly suppressed and the battery performance is improved, and the amount of hydrogen gas generated and the battery performance are maintained at a high level for a long period of time.Alkaline batteries and their Regarding negative electrode active materials.

[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 Unexamined Patent Publication No. 181266/1983). Further, zinc alloy powders to which gallium, aluminum, bismuth, 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 ultra-low mercury content of 0.2% by weight or less, the effect of mercury in item (3) is no longer fully exerted, resulting in deterioration of discharge performance. It is thought that then.

Therefore, as a means to solve the above problem, it is effective to add a surfactant to the negative electrode material.

This is considered to be because the surfactant is adsorbed on the surface of the zinc alloy powder and contributes to improving the corrosion resistance of the zinc alloy powder. By this means, even though the mercury content is significantly reduced in alkaline cells, hydrogen gas generation rates and discharge performance approximately equivalent to those of conventional high mercury contents can be achieved.

However, in an alkaline battery having a negative electrode material containing the above-mentioned surfactant, when stored at room temperature for a long period of time, the effect of the surfactant decreases, hydrogen gas generation rate increases, and discharge performance deteriorates. Tend. This is thought to be because the surfactant adsorbed on the surface of the zinc alloy powder gradually desorbs when it remains in the electrolyte for a long period of time.

In view of the current situation, the present invention provides an alkaline battery and its negative electrode in which hydrogen gas generation is stably suppressed over a long period of time while the mercury content is significantly reduced, and discharge performance is maintained at a high level for a long period of time. The purpose is to provide active materials.

[Means for Solving the Problems] As a result of intensive research in line with this objective, the present inventors added a silane coupling agent and a surfactant to a negative electrode active material made of zinc alloy powder or an electrolytic solution made of an alkaline aqueous solution. By adding these agents, hydrogen gas generation is significantly suppressed and discharge performance is improved compared to when no additives are added, and the amount of hydrogen gas generated and discharge performance are maintained at a high level over a long period of time. The inventors have discovered that an alkaline battery can be obtained and have arrived at the present invention.

That is, the alkaline battery of the present invention is an alkaline battery having a negative electrode material containing a silane coupling agent and a surfactant in addition to a zinc alloy powder and an electrolyte.

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 includes lead, bismuth, indium,
Examples include those containing a certain amount of at least one of aluminum, calcium, cadmium, tin, gallium, nickel, silver, etc. The method for producing this zinc alloy powder includes, for example, adding a predetermined amount of additional elements such as lead, indium, and bismuth to molten zinc, stirring to form an alloy, and then atomizing with compressed air to form a powder. The powder obtained by sieving and sizing is used. The content of each additional element in this zinc alloy powder is generally 0.001 to 0.5% by weight.

In the present invention, a 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, for example, 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. A zinc chloride alloy powder obtained by wet freezing with a desired amount of mercury in an alkaline solution may be used; in this case, the mercury content in the zinc chloride alloy powder is lower than the conventional one, i.e. 3.0 wt. % or less, and in consideration of low pollution, it is more preferably 1.5% by weight or less.

The silane coupling agent used in the present invention is a silicon compound that has the ability to chemically bond organic substances and inorganic materials, and a typical example thereof is the following general formula
: X-3iR.

Or the following general formula ■: R35t-X-8iR3 Examples include compounds represented by: General formula I above.

In (2), X represents an organic functional group selected from an amino group, a vinyl group, an epoxy group, a mercapto group, a chloro group, an alkylene group, a polymethylene group, an alkoxy group, an alkyl group, etc., or a combination thereof. Moreover, the above general formula 1. In II, R represents an alkoxy group, an alkyl group, etc., preferably a group that allows the compound to be hydrolyzed, and particularly preferably a methoxy group, an ethoxy group, or a methyl group.

Specifically, such silane coupling agents include γ-(2-aminoethyl)aminopropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, and methyltrimethoxysilane. Methoxysilane and hexamethyldisilazane are preferred.

Note that the silane coupling agent used in the present invention may be any one of the above-mentioned silane coupling agents, or may be a mixture of two or more.

In addition, the surfactants used in the present invention include anionic, cationic, nonionic, or amphoteric surfactants, and specifically, higher fatty acid alkali salts, alkyl sulfates, alkyl sulfonic acid salt, alkylaryl sulfonate, sulfosuccinate ester salt, alkoxypolyethylene oxide sulfonate, alkylphenyl poly, ethylene glycol ether sulfate ester salt, polyoxyethylene alkyl ether phosphate ester, polyoxyethylene alkyl ether phosphate ester salt, Polyoxyethylene alkyl ether sulfate triethanol ammonium salt, acyl methyl taurate,
Acyl sarcosinate, acyl sarcosine, higher amine halide, alkyl pyridinium halide, quaternary ammonium salt, polyethylene glycol alkyl ether, polyethylene glycol fatty acid ester, polyoxyethylene difatty acid ester, polyoxyethylene polyoxyalkylene alkyl ether, sorbitan Fatty acid ester, polyoxyethylene sorbitan fatty acid ester, fatty acid monoglyceride, polyglycerin fatty acid ester, fluorinated alkyl ester, perfluoroalkyl(poly)methylene(poly)oxyalkylene fatty acid ester, polyoxyethylene alkylamine, fatty acid jetanolamide, ethylene Bis fatty acid amine, amino acid, dimethylalkyl betaine, 2-alkyl-N-
Examples include sodium hydroxypolymethylene-N-hydroxyethylimidazolinium betaine hydroxide.

Incidentally, the surfactant used in the present invention may be any one of the above surfactants, or two types of surfactants.
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 silane coupling agent and surfactant described above. These can be added by coating zinc alloy powder with a silane coupling agent and surfactant and using this as the negative electrode active material, or by coating the silane coupling agent and surfactant with an aqueous solution of potassium hydroxide, Examples include a method of adding zinc alloy powder to an electrolytic solution such as an aqueous sodium solution or a gelling agent, but in the present invention, zinc alloy powder is added to a solvent such as toluene to which a silane coupling agent and/or a surfactant are added. After adding and mixing, the solvent is dried and evaporated to form a coating layer of a silane coupling agent and a surfactant on the surface of the zinc alloy powder simultaneously or sequentially (the order does not matter), and this is used as a negative electrode active material. However, the effect of suppressing hydrogen gas generation,
Most preferred from the viewpoint of improving discharge performance.

In addition, in the present invention, mercury is added and mixed into the electrolytic solution that forms the negative electrode material together with the zinc alloy powder on which a coating layer of the above-mentioned silane coupling agent and surfactant is formed. Good too.

Here, the amounts of the silane coupling agent and surfactant added to the negative electrode material are not particularly limited, and are appropriately selected so as to obtain an alkaline battery with good characteristics, but are preferably zinc alloy powder. The amount of silane coupling agent added is 0.001 to 1.0 parts by weight, and the amount of surfactant added is also the same <0.001-1.0 parts by weight per 100 parts of ffi.
It is 0 parts by weight. If the amount of each of the silane coupling agent and the surfactant added is less than o and oot parts by weight, it tends to be difficult to obtain the effects of the present invention, such as improving the corrosion resistance of zinc and preventing hydrogen gas generation. If the amount exceeds 1 part by weight, the silane coupling agent and/or surfactant present in the coating layer of the silane coupling agent and surfactant formed on the surface of the zinc alloy powder, the electrolyte, etc. It may act as a barrier and inhibit the dissolution reaction of zinc, and good discharge performance may not be obtained.

Furthermore, in the present invention, a solvent, a dispersant, etc. may be mixed with the silane coupling agent and surfactant as needed, as long as the properties of the silane coupling agent and surfactant are not impaired. do not have.

Although the effects of the added silane coupling agent and surfactant have not been fully elucidated, it is estimated that
During battery storage, the silane coupling agent is adsorbed on the surface of the zinc alloy powder, and since the silane coupling agent has excellent heat resistance and exists relatively stably even in alkaline electrolytes, the zinc alloy powder remains stable for a long period of time. Present on the powder surface. Further, as mentioned above, surfactants have a remarkable effect on improving the corrosion resistance of zinc. Furthermore, it is believed that the silane coupling agent acts to bind the zinc alloy powder and the surfactant. These interactions have the effect of stably improving the corrosion resistance of zinc over a long period of time, suppressing the generation of hydrogen gas that accompanies corrosion of zinc, and also suppressing the hydrogen gas bubbles that were conventionally seen during electrical discharge. It is thought that the discharge performance is improved and maintained for a long period of time because the negative effects such as inhibition of electrical contact between zinc alloy powder particles are suppressed.

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

Examples 1 to 12 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
It was powdered using Ng/ci). This powder is 50 to 1
Zinc alloy powder was obtained by sieving to a particle size range of 50 mesh.

Next, mercury was added to the above powder in an alkaline solution of 10% potassium hydroxide so that the content ratio was as shown in Table 1, and the oxidized zinc alloy powder shown in Table 2 was obtained. Ta.

Next, the above glazed zinc alloy powder was added to a toluene solvent in which the silane coupling agent shown in Table 1 was added and dissolved, and the toluene was dried and volatilized while mixing. A coating layer of the silane coupling agent shown in Table 1 was formed in the ratio shown in Table 1. Next, on the surface of the frozen zinc alloy powder having the coating layer of the silane coupling agent, a coating layer of the surfactant shown in Table 1 was applied in the same manner as in the case of the silane coupling agent at the ratio shown in Table 1. This was formed to give a negative electrode active material.

Further, an electrolytic solution was prepared by adding about 1.0% of carboxymethyl cellulose and sodium polyacrylate as gelling agents to a 40% potassium hydroxide aqueous solution saturated with zinc oxide.

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. IL
It is composed of an outer can 12.

The discharge load was 2Ω for this alkaline manganese battery immediately after manufacture (first time) and after storage at 60°C for 30 days.
The discharge duration up to the final voltage of 0.9 V was measured under the discharge conditions of 20°C, and the glazed zinc alloy powder with a mercury content of 5.0% by weight was coated with no silane coupling agent or surfactant. It is expressed as an index with the initial measurement value of the alkaline manganese battery in Comparative Example 3 used as the negative electrode active material set as 100.

The results are shown in Table 1.

Regarding the above negative electrode material, the amount of gas generated (μQ/g-day) after 20 days and 40 days at 60°C was
The results are shown in Table 1.

Example 13 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, 3.0 II g of the same silane coupling agent as in Example 2, and The discharge duration and gas generation rate were measured in the same manner as in Example 2, except that the negative electrode material was made by adding and mixing surfactant 3.0 + ag and gelatinized, and the results were summarized in the first example. Shown in the table.

(structural formula; The negative electrode materials of Examples 1 to 12 used as substances had a composition of the frozen zinc alloy powder that was the negative electrode active material, compared to the negative electrode material of Comparative Example 1 in which a silane coupling agent and a surfactant were not added. Regardless of the difference and the type of silane coupling agent and surfactant used, the hydrogen gas generation rate is significantly reduced,
Moreover, alkaline batteries incorporating this negative electrode material had extremely excellent discharge performance. Furthermore, in the negative electrode materials of Examples 1 to 12, zinc chloride alloy powder with a mercury content of 50 times (5.0% by weight) was used as a negative electrode active material without coating with a silane coupling agent or a surfactant. The hydrogen gas generation rate was lower than that of the negative electrode material of Comparative Example 3 used, and the discharge performance of alkaline batteries was also excellent.

In addition, the negative electrode materials of Examples 1 to 12 were stable for a long period of time in which the hydrogen gas generation rate was reduced compared to the negative electrode material of Comparative Example 2 which was not coated with a silane coupling agent. Furthermore, the discharge performance of alkaline batteries incorporating this negative electrode material was also maintained at a high level over a long period of time.

Furthermore, Example 13 uses a negative electrode material in which a silane coupling agent and a surfactant are added and mixed into an alkaline aqueous solution as an electrolytic solution, but in this case as well, hydrogen gas generation occurs over a long period of time. This was stably suppressed, and the discharge performance of alkaline batteries incorporating this negative electrode material was also maintained at a high level over a long period of time.

[Effects of the Invention] As explained above, according to the alkaline battery of the present invention having a negative electrode material to which a silane coupling agent and a surfactant are added, when the mercury content is lowered than before, the mercury content is particularly low. The proportion of zinc alloy powder is 0.2ffiffi
Even when the amount of mercury is extremely low, such as % or less, hydrogen gas generation within the battery is significantly suppressed, battery performance is improved, and this state is maintained at a high level for a long period of time.

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 silane coupling agent and a surfactant.

[Brief explanation of drawings]

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

Claims (1)

[Claims] 1. An alkaline battery having a negative electrode material containing a silane coupling agent and a surfactant in addition to zinc alloy powder and an electrolyte. 2. A negative electrode active material for alkaline batteries comprising a zinc alloy powder coated with a silane coupling agent and a surfactant.