JP6734155B2 - Alkaline battery - Google Patents

Description

TECHNICAL FIELD The present invention relates to an alkaline battery that has good medium-load discharge characteristics and a small amount of gas generated in the battery during overdischarge.

An alkaline battery using zinc as a negative electrode active material is used as a power source for various electronic devices, and various characteristics are required according to its use. Until now, development was mainly promoted for applications that require a relatively large current, such as digital cameras, cameras with flash, portable TVs, and emergency chargers.

For example, in Patent Document 1, the water content of any one of the positive electrode mixture, the positive electrode pellets, and the positive electrode is measured, and the injection amount of the alkaline electrolyte is determined according to the water content, thereby varying the water content of the entire battery. It has been proposed to produce an alkaline battery that suppresses the above and has excellent heavy load discharge characteristics.

In Patent Document 2, 100 ppm or more of Al is contained in the zinc alloy powder, and the amount of water in the battery system is 0.250 to 0.300 g per 1 g of the positive electrode active material (or 0.6 per 1 g of the zinc alloy powder). ~ 0.7 g), it is proposed to improve the utilization efficiency of water during discharge of the battery, have excellent heavy load discharge characteristics, and suppress the gas generation during overdischarge. ing.

On the other hand, in Patent Document 3, in order to prevent the deterioration of the discharge performance after storage, by adding a granular water-absorbing polymer obtained by removing the uncrosslinked portion of the polyacrylate as a gelling agent to the gelled negative electrode, It has been proposed to avoid deterioration of discharge performance of an alkaline battery after storage and troubles in the manufacturing process.

JP, 2013-45619, A JP, 2010-118285, A JP, 10-50303, A

However, recently, the proportion of alkaline batteries used in devices requiring large current as described above has decreased, and instead, in devices requiring relatively small current, such as LED lights and health appliances. Due to the increased use, it is necessary to consider a battery design having excellent discharge characteristics at medium load, unlike the conventional battery design optimized for heavy load applications.

Further, in order to further improve the reliability of the battery, it is still required to suppress gas generation in the battery during over-discharge, for example.

The present invention has been made in view of the above circumstances, by improving the utilization efficiency of the active material in the negative electrode of the alkaline battery, to improve the characteristics in medium-load discharge, gas generation in the battery during over-discharge The purpose is to suppress and improve reliability.

The alkaline battery of the present invention that can achieve the above object is a zinc alloy powder, a negative electrode containing a granular water-absorbing polymer, an alkaline electrolyte, a positive electrode and a separator, wherein the zinc alloy powder is , 0.005 to 0.015 mass% of Al, 0.005 to 0.015 mass% of Bi, 0.02 to 0.04 mass% of In, and 0.0001 to 0.003 mass% of Mg, respectively. In the zinc alloy powder, the proportion of the powder that passes through the 50-mesh sieve is 98 mass% or more of the entire zinc alloy powder, and the proportion of the powder that passes through the 200-mesh sieve is zinc alloy. It is 15% by mass or less of the whole powder, and the content of the granular water-absorbing polymer in the negative electrode is 0.75 to 1.1 parts by mass with respect to 100 parts by mass of the zinc alloy powder. And

According to the present invention, it is possible to provide an alkaline battery that has good medium-load discharge characteristics and a small amount of gas generated in the battery during overdischarge.

It is sectional drawing which shows an example of the alkaline battery of this invention. It is sectional drawing which shows the other example of the alkaline battery of this invention.

In the conventional alkaline battery, in order to improve the heavy load discharge characteristics, the amount of water is examined from the viewpoint of improving the reaction efficiency of the positive electrode, and for the negative electrode, the particle size of the zinc alloy powder that is the active material is reduced to reduce the reaction area. It has been dealt with so that the desired characteristics can be obtained by increasing.

On the other hand, the present inventors have found that as the discharge progresses, the water content in the negative electrode decreases and an active material that does not contribute to the discharge reaction is generated, which reduces the utilization rate of the negative electrode active material and reduces the load under medium load discharge. I noticed that it is one of the causes of the deterioration of the characteristics. Therefore, in order to improve the medium-load discharge characteristics, the present inventors reconsidered the design of the battery so that the necessary water content was maintained in the negative electrode even when the discharge proceeded.

However, increasing the amount of electrolyte in the entire battery to increase the amount of water contained in the negative electrode increases the possibility of battery leakage unless the filling amount of the positive electrode or negative electrode is reduced. Will end up.

On the other hand, if the amount of water contained in the negative electrode is increased by changing the distribution of the electrolytic solution between the positive electrode and the negative electrode without increasing the total amount of electrolytic solution in the battery, the water necessary for the reaction of the positive electrode is insufficient. However, the reaction efficiency of the positive electrode is reduced and the discharge capacity is reduced.

The present inventors have examined the battery configuration that can improve the utilization rate of the active material of the negative electrode without causing the above-mentioned problems, and as a result, in the zinc alloy powder that is the negative electrode active material, the type of additive element and its Adjusting the content and reducing the proportion of fine particles and coarse particles, and a certain amount of water is retained in the negative electrode even when the discharge has progressed, and the water necessary for the reaction is supplied to the negative electrode active material. As described above, the granular water-absorbing polymer that absorbs water of the electrolytic solution and swells is contained in the negative electrode at a constant ratio with respect to 100 parts by mass of the zinc alloy powder. I figured out what I could do.

That is, in the zinc alloy powder used for the negative electrode of the present invention, Al is 0.005 to 0.015 mass% (50 to 150 ppm), Bi is 0.005 to 0.015 mass% (50 to 150 ppm), In. Is 0.02 to 0.04 mass% (200 to 400 ppm), and Mg is 0.0001 to 0.003 mass% (1 to 30 ppm). Al is preferably 0.007 to 0.013 mass %, Bi is preferably 0.007 to 0.013 mass %, and In is 0.025 to 0.035 mass %. It is preferable that Mg is 0.0003 to 0.002 mass %.

If the amount of the additive element is too small, the effect of the present invention will be insufficient, and if it is too large, the degree of segregation will be large, which will cause deterioration of the discharge characteristics of the battery or promotion of gas generation.

In addition, the zinc alloy related to the zinc alloy powder typically contains Zn and unavoidable impurities other than the above alloy elements, but contains other alloy elements such as Ca within a range that does not impair the effects of the present invention. You may have.

Further, in the zinc alloy powder used for the negative electrode of the present invention, the proportion of the powder that passes through the 50-mesh sieve is 98% by mass or more, preferably 98.5% by mass or more, and more preferably the mass of the entire zinc alloy powder. 99 mass% or more. That is, the particle size of the zinc alloy powder is adjusted so that substantially all of the zinc alloy powder passes through the 50-mesh sieve. On the other hand, the proportion of the powder that passes through the 200-mesh sieve is set to 15% by mass or less, preferably 12% by mass or less, and more preferably 9% by mass or less. That is, the particle size distribution is adjusted so that the particle size of most of the zinc alloy powder exists between 50 mesh and 200 mesh.

The 50 mesh corresponds to a sieve opening of 300 μm, and the 200 mesh corresponds to a sieve opening of 75 μm.

Thereby, the discharge reaction in the negative electrode easily progresses uniformly, and it becomes possible to discharge efficiently with a smaller content of water. In addition, since the variation in the depth of discharge of each zinc alloy powder is reduced, it is possible to prevent the generation of powder that is more likely to generate gas because the discharge is less likely to proceed than other powders. It is also possible to suppress the amount of gas generated in the battery.

Here, the granular water-absorbing polymer that absorbs water and swells in the negative electrode in an amount of 0.75 parts by mass or more, preferably 0.8 parts by mass or more, more preferably 0.1 part by mass with respect to 100 parts by mass of the zinc alloy powder. By containing 85 parts by mass or more, the granular water-absorbing polymer can hold the electrolytic solution (water) necessary for discharge. Therefore, even if the flowable electrolytic solution in the negative electrode is reduced due to the progress of discharge and the distribution of the electrolytic solution is likely to be biased, the electrolytic solution held by the granular water-absorbing polymer gradually enters the negative electrode. Since it is supplied, the discharge reaction of the zinc alloy powder can proceed in the entire negative electrode, the utilization factor of the negative electrode can be improved, and the medium-load discharge characteristics can be improved.

However, if the content of the granular water-absorbing polymer is too large, the electrolytic solution is retained in the granular water-absorbing polymer more than necessary, and the flowable electrolytic solution is insufficient, resulting in an increase in the reaction resistance of the negative electrode, zinc, etc. The content of the granular water-absorbing polymer in the negative electrode is the zinc alloy powder because the filling amount of the alloy powder is reduced or the fluidity of the gelled negative electrode mixture described below is deteriorated and the productivity is deteriorated. The amount is 1.1 parts by mass or less, preferably 1.05 parts by mass or less, and more preferably 1 part by mass or less, relative to 100 parts by mass.

The content ratio of the granular water-absorbing polymer in the negative electrode means the ratio in a dry state before absorbing the electrolytic solution.

Further, in the process in which zinc oxide, which is a reaction product, is generated and diffuses as ions along with the discharge of the negative electrode, a part of the zinc oxide remains on the surface of the zinc alloy, hinders the discharge reaction, and reduces the resistance of the negative electrode. It is known to raise the temperature and cause a decrease in the utilization factor of the negative electrode. The present inventors considered that it is necessary to facilitate the diffusion of the reaction product of the negative electrode in the negative electrode configuration in order to further improve the medium-load discharge characteristics, and further studied the negative electrode configuration. It was

As a result, when the alkaline electrolyte contained in the negative electrode is an aqueous solution containing potassium hydroxide in a concentration of 33% by mass or more, preferably 33.5% by mass or more, oxidation to the surface of the zinc alloy is performed. We have found that it is possible to suppress the deterioration of the discharge characteristics due to the precipitation of zinc. The alkaline electrolyte contained in the negative electrode is increased in potassium hydroxide concentration as the discharge reaction proceeds, and the concentration of the alkaline electrolyte used for forming the positive electrode mixture described later is the concentration of the alkaline electrolyte contained in the negative electrode. If it is higher than the above, the concentration gradually increases after the battery is assembled. However, at least at the time of assembling the battery, the concentration of potassium hydroxide in the alkaline electrolyte contained in the negative electrode is preferably 38% by mass or less in order to improve the ionic conductivity, and 36.5% is preferable. The content is more preferably not more than mass%, and most preferably not more than 35 mass%.

Hereinafter, the structure of the alkaline battery of the present invention will be described in detail.

<Negative electrode>
A gelled negative electrode mixture (gelled negative electrode) containing the zinc alloy powder, the granular water-absorbing polymer, and an alkaline electrolyte is used for the negative electrode in the alkaline battery of the present invention.

As described above, the zinc alloy powder has a particle size adjusted so that the proportion of coarse particles and fine particles is reduced, but in order to further improve the effect of the present invention, its average particle size is: The thickness is preferably 120 μm or more, more preferably 150 μm or more, while it is preferably 200 μm or less, more preferably 185 μm or less.

The granular water-absorbing polymer is not particularly limited as long as it absorbs an alkaline electrolyte and swells when forming a negative electrode mixture and can retain the water necessary for the reaction in the negative electrode. Preferably used are (meth)acrylic acid and crosslinked products thereof, and poly(meth)acrylic acid salts and crosslinked products thereof. The poly(meth)acrylic acid and the poly(meth)acrylic acid salt may contain monomer components other than (meth)acrylic acid and the (meth)acrylic acid salt. Examples of poly(meth)acrylic acid salts include alkali metal salts and ammonium salts, and sodium salts and potassium salts are preferably used.

By using the water-absorbing polymer in the form of granules having excellent liquid retention properties, it becomes possible to sufficiently retain the water necessary for the reaction of the negative electrode active material.

The average particle size of the granular water-absorbing polymer is preferably 50 μm or more, more preferably 100 μm or more, and more preferably 150 μm or more in order to easily hold the zinc alloy powder in the negative electrode. Most preferred. On the other hand, in order not to hinder the discharge reaction, it is preferably 700 μm or less, more preferably 500 μm or less, and most preferably 300 μm or less.

The alkaline electrolyte to be contained in the negative electrode is not particularly limited, and is similar to the electrolytes used in conventionally known alkaline batteries and alkaline storage batteries (for example, potassium hydroxide, lithium hydroxide, water). Although an alkaline aqueous solution such as an aqueous solution of an alkali metal hydroxide such as sodium oxide) can be used, it is an aqueous solution containing at least potassium hydroxide from the viewpoint of facilitating the diffusion of the reaction product of the negative electrode described above. An aqueous solution having a concentration of 33% by mass or more is used.

The negative electrode for the alkaline battery of the present invention may contain various additives as they are or in the state of being dissolved in the alkaline electrolyte. As the additive, an indium compound or a zinc compound is preferably used.

By including an indium compound in the negative electrode, In is segregated on the surface of the zinc alloy powder, and the effect of suppressing discharge gas deposition on the surface of the zinc alloy powder and gas generation due to corrosion of the zinc alloy powder can be expected. .. Examples of the indium compound include indium oxide and indium hydroxide. The content of the indium compound is preferably 0.003 to 0.05 parts by mass with respect to 100 parts by mass of the zinc alloy powder.

In addition, by including a zinc compound in the negative electrode, an effect of suppressing gas generation due to corrosion of the zinc alloy powder can be expected. As the zinc compound, for example, compounds such as zinc oxide, zinc silicate, zinc titanate, and zinc molybdate can be used, and it is preferable that the zinc compound is contained in a state of being dissolved in an alkaline electrolyte, and particularly zinc oxide. Is preferably used.

The content of the zinc compound is preferably 1 to 4% by mass, and more preferably 2.5 to 3.5% by mass when dissolved in an alkaline electrolyte and used.

The negative electrode for the alkaline battery of the present invention preferably contains a thickener that is soluble in the alkaline electrolyte in order to keep the viscosity in the gelled state within a suitable range. Examples of the thickener include celluloses such as poly(meth)acrylic acid, poly(meth)acrylic acid salt, carboxymethylcellulose, methylcellulose, and hydroxypropylcellulose, or salts thereof, and crosslinked branched poly(meth). Acrylic acid and crosslinked branched poly(meth)acrylic acid salts are preferably used. Examples of the poly(meth)acrylic acid salt and the salts of celluloses include alkali metal salts and ammonium salts, and sodium salts and potassium salts are preferably used.

The content of the thickener in the negative electrode is preferably 0.15 parts by mass or more based on 100 parts by mass of the zinc alloy powder in order to sufficiently increase the viscosity of the negative electrode mixture, The amount is more preferably not less than 0.3 parts by mass, and more preferably not more than 0.35 parts by mass, and more preferably not more than 0.3 parts by mass, in order to impart a certain degree of fluidity to the negative electrode mixture.

Further, the total content of the granular water-absorbing polymer and the thickener is preferably 0.95 to 1.35 parts by mass with respect to 100 parts by mass of the zinc alloy powder, and is 1 part by mass or more. It is more preferable that it is 1.05 parts by mass or more, most preferably 1.35 parts by mass or less, and most preferably 1.25 parts by mass or less.

The zinc alloy powder, the granular water-absorbing polymer, the alkaline electrolyte, the thickener and the like are mixed to form a gelled negative electrode mixture, which is used as the negative electrode of the alkaline battery of the present invention. The content of the zinc alloy powder in the negative electrode mixture is, for example, preferably 60% by mass or more, more preferably 65% by mass or more, and preferably 75% by mass or less. More preferably 70% by mass or less.

<Positive electrode>
The positive electrode according to the alkaline battery of the present invention is, for example, a positive electrode active material, a conductive auxiliary agent, and further mixed with an alkaline electrolyte and a binder for molding to obtain a positive electrode mixture, and the positive electrode mixture is formed into a ring shape or the like. It is formed by pressure molding.

As the positive electrode active material, manganese oxide such as manganese dioxide, nickel oxide such as nickel oxyhydroxide, silver oxide such as silver oxide and the like can be used, but manganese dioxide is preferably used.

The positive electrode active material preferably has a BET specific surface area of 20 m ² /g or more, and more preferably 25 m ² /g or more, in order to make the reaction area constant or more and increase the reaction efficiency.

On the other hand, it is desirable to improve the characteristics on the positive electrode side as well as the characteristics of the negative electrode. By setting the BET specific surface area of the positive electrode active material to 40 m ² /g or less, preferably 35 m ² /g or less, It is desirable to improve moldability and increase the density of the mixture. This makes it possible to increase the filling amount of the positive electrode active material to increase the capacity of the positive electrode and to improve the characteristics of the negative electrode.

The BET specific surface area of the positive electrode active material referred to here is a specific surface area of the surface of the active material and the micropores, which is obtained by measuring and calculating the surface area by using the BET formula which is a theoretical formula for the adsorption of multiple layers. .. Specifically, it is a value obtained as a BET specific surface area by using a specific surface area measuring device by a nitrogen adsorption method (for example, Macsorb HM modelle-1201 manufactured by Mountech Co., Ltd.).

In addition, the average particle diameter of the positive electrode active material is preferably 45 μm or less, and more preferably 40 μm or less in order to keep the reaction area above a certain level and enhance the reaction efficiency. On the other hand, in order to improve the moldability of the positive electrode mixture and increase the density of the mixture, it is preferably 30 μm or more, and more preferably 33 μm or more.

As the conductive additive for the positive electrode, for example, graphite, Ketjen black, acetylene black or the like can be used. From the viewpoint of improving conductivity, the amount of the conductive additive in the positive electrode mixture is preferably 3 parts by mass or more, and more preferably 4.5 parts by mass or more, relative to 100 parts by mass of the positive electrode active material. Most preferably 6 parts by mass or more. On the other hand, in order to secure the capacity of the positive electrode, the amount is preferably 10 parts by mass or less, more preferably 8.5 parts by mass or less, and even 7 parts by mass or less with respect to 100 parts by mass of the positive electrode active material. Is most preferred.

As the binder for the positive electrode, for example, polytetrafluoroethylene, polyvinylidene fluoride, styrene butadiene rubber, etc. can be used. The amount of binder in the positive electrode mixture is preferably 0.1 to 1% by mass, for example.

Examples of the alkaline electrolyte used for the positive electrode include an alkaline aqueous solution in which a hydroxide of an alkali metal such as potassium hydroxide, sodium hydroxide or lithium hydroxide is dissolved in water, or a solution in which zinc oxide or the like is added. Although used, a potassium hydroxide aqueous solution is more preferable from the viewpoint of enhancing the discharge characteristics of the battery. The concentration of the alkali metal hydroxide in the electrolytic solution is preferably 40 to 60% by mass in the case of potassium hydroxide, and when zinc oxide is used, the concentration is 1.0 to It is preferably 4.0% by mass.

The average particle diameter used in the present invention is a value represented as a volume average particle diameter (D50) obtained by measuring a particle size distribution using a particle size distribution meter.

<Electrolyte>
Alkaline electrolytes for injecting into the battery other than being used for the positive electrode and the negative electrode, for example, as the alkaline electrolytes to be absorbed by the separator, similar to the electrolytes relating to the positive electrode and the negative electrode, for example, hydroxide It is possible to use an alkaline aqueous solution consisting of an aqueous solution of an alkali metal hydroxide such as potassium, sodium hydroxide or lithium hydroxide, or one to which zinc oxide is added, but the same as the alkaline electrolyte used for the negative electrode It is preferable to have a configuration.

<Separator>
There is no particular limitation on the separator relating to the alkaline battery of the present invention. -Linter pulp paper, vinylon-mercerized pulp paper, etc. can be used. Also, a separator obtained by stacking a hydrophilic microporous polyolefin film (such as a microporous polyethylene film or a microporous polypropylene film), a cellophane film and a liquid absorbing layer such as vinylon/rayon mixed paper may be used. ..

<Amount of water in battery system>
For example, the discharge reaction of an alkaline battery using manganese dioxide as the positive electrode active material and zinc as the negative electrode active material proceeds according to the following formula (1).

2MnO ₂ + Zn + H ₂ O → MnOOH + ZnO (1)

As is clear from the above formula (1), in an alkaline battery, since water is consumed during discharging, it is desirable that a certain amount of water or more exists in the battery from the viewpoint of discharge reaction. In an alkaline battery, the amount of water in the battery system is preferably 0.23 g or more, and more preferably 0.245 g or more, per 1 g of the positive electrode active material. Alternatively, the water content in the battery system is preferably 0.585 g or more, and more preferably 0.6 g or more, per 1 g of the zinc alloy powder contained in the negative electrode.

On the other hand, in order to easily suppress gas generation in the battery (especially gas generation in the battery during overdischarge), it is desirable to reduce excess water that is not involved in the reaction as much as possible. Is preferably 0.27 g or less, and more preferably 0.26 g or less, per 1 g of the positive electrode active material. Alternatively, the amount of water in the battery system is preferably 0.675 g or less, and more preferably 0.66 g or less, per 1 g of the zinc alloy powder contained in the negative electrode.

By adjusting the amount of water in the battery system as described above, it is easy to configure an alkaline battery that has good medium-load discharge characteristics and produces a small amount of gas in the battery during overdischarge.

<Structure of alkaline battery and other components>
The shape and the like of the alkaline battery of the present invention are not particularly limited, but examples thereof include a cylindrical shape (cylindrical shape, rectangular tube shape, etc.). Hereinafter, the structure of the battery of the present invention will be described with reference to the drawings. FIG. 1 is a sectional view showing an example of the alkaline battery of the present invention. In the alkaline battery of FIG. 1, a ring-shaped positive electrode 2 (positive electrode mixture molded body) is arranged in an outer can 1 made of metal (such as iron plated with Ni and stainless steel). A cup-shaped separator 3 is arranged inside, and an alkaline electrolyte (not shown) is injected from inside the separator 3. Further, the inside of the separator 3 is filled with a negative electrode 4 (gelled negative electrode mixture) containing zinc alloy powder. 1b in the outer can 1 is a positive electrode terminal. A negative electrode terminal plate 7 made of metal (Ni-plated iron, stainless steel, etc.) is arranged at the open end portion 1a of the outer can 1, and the outer peripheral edge portion 62 of the resin sealing body 6 is interposed therebetween. The open end portion 1a is bent inward and sealed. A negative electrode current collector rod 5 made of metal (such as brass plated with Sn) is welded to the negative electrode terminal plate 7 at its head, and the negative electrode current collector rod 5 is provided in the central portion 61 of the sealing body 6. It is inserted into the negative electrode 4 through the through hole 64. Further, a metal washer 9 (a disk-shaped metal plate) is arranged as a support means for preventing the negative electrode terminal plate 7 from being deformed at the time of sealing and supporting the sealing body 6 from the inside. The resin sealing body 6 is formed with an explosion-proof thin portion 63. When gas is generated in the battery at the time of short circuit, the thin portion 63 of the sealing body 6 is preferentially cleaved, and the gas is moved to the metal washer 9 side through the generated crack. The metal washer 9 and the negative electrode terminal plate 7 are provided with gas vent holes (not shown), and gas inside the battery is discharged to the outside of the battery through these gas vent holes. Examples of the resin that constitutes the resin sealing body 6 include nylon 66.

FIG. 2 shows a cross-sectional view of another example of the alkaline battery of the present invention. In FIG. 2, elements having the same operations as in FIG. 1 are designated by the same reference numerals to avoid redundant description. In FIG. 2, reference numeral 8 is an insulating plate for insulating the outer can 1 and the negative electrode terminal plate 7, and 20 is a body portion accommodating the power generation element.

In the alkaline battery shown in FIG. 1, since the metal washer 9 is used, the volume occupied by the sealing portion (10 in FIG. 1) becomes large. On the other hand, by eliminating the metal washer and using the negative electrode terminal plate 7 as the supporting means for supporting the sealing body 6 from the inside like the battery of FIG. 2, the volume occupied by the sealing portion 10 is reduced and the power generating element is The volume of the body portion 20 that can be accommodated can be increased, and the filling amount of each mixture of the positive electrode 2 and the negative electrode 4 can be increased as compared with the battery of FIG. 1.

(Example 1)
<Formation of positive electrode mixture>
Manganese dioxide containing 1.6% by mass of water (average particle size: 36.5 μm, BET specific surface area: 31 m ² /g), graphite, zinc oxide, polytetrafluoroethylene powder, and an alkaline electrolyte for preparing a positive electrode mixture (Aqueous solution containing 56% by mass of potassium hydroxide and 2.9% by mass of zinc oxide) at a mass ratio of 100:7.7:0.2:0.2:6.9 at a temperature of 50°C. To prepare a positive electrode mixture. The concentration of potassium hydroxide in the electrolytic solution contained in the positive electrode mixture was 45.4 mass% in consideration of the water content of manganese dioxide.

<Formation of negative electrode mixture>
Zinc alloy containing Al at 0.01 mass% (100 ppm), Bi at 0.01 mass% (100 ppm), In at 0.03 mass% (300 ppm), and Mg at 0.0005 mass% (5 ppm). And a crosslinked product of granular sodium polyacrylate having an average particle diameter of 500 μm, polyacrylic acid and an alkaline electrolyte for preparing a negative electrode mixture (potassium hydroxide: 34% by mass, and zinc oxide: 2. An aqueous solution containing 9% by mass) was mixed at a mass ratio of 100:0.91:0.24:48.1 to prepare a gelled negative electrode mixture.

The zinc alloy powder had an average particle size of 170 μm, the proportion of the powder that passed through the 50-mesh sieve was 98.7% by mass of the whole powder, and the proportion of the powder that passed through the 200-mesh sieve. Was 11 mass% of the whole powder.

<Production of battery>
As an outer can, an outer can 1 for AA alkaline batteries, which is made of a killed steel plate having a matte Ni plating on the surface and has a shape shown in FIG. 2, was prepared. This outer can 1 has a sealing portion 10 having a thickness of 0.25 mm and a body portion 20 having a thickness of 0.16 mm. Further, in order to prevent the positive electrode terminal 1b from being dented when the battery is dropped, The can thickness of the part is the same as the sealing part. Using this outer can 1, an alkaline battery was manufactured as follows.

11.1 g of the positive electrode mixture is inserted into the outer can 1 and pressure-molded into a bobbin shape (hollow cylindrical shape), and the inner diameter is 9.1 mm, the outer diameter is 13.7 mm, and the height is 13.9 mm. The three positive electrode material mixture molded bodies (density: 3.28 g/cm ³ ) were prepared in a stacked state. Next, a groove is formed at a position of 3.5 mm in the height direction from the opening end of the outer can 1, and in order to improve the adhesion between the outer can 1 and the sealing body 6, the inner side of the outer can 1 is reached to this groove position. Pitch was applied to.

Next, a nonwoven fabric composed of acetalized vinylon and tencel having a thickness of 100 μm and a basis weight of 30 g/m ² is triple-layered and wound in a tubular shape, the bottom portion is bent, and this portion is heat-sealed, and one end is closed. The resulting cup-shaped separator 3 was obtained. This separator 3 is loaded inside the positive electrode 1 inserted in the outer can 1, and an alkaline electrolyte (34% by mass of potassium hydroxide and 2.9% by mass of zinc oxide is contained therein for absorbing the liquid in the separator. 1.33 g of the above aqueous solution) was injected into the inside of the separator, and further 5.74 g of the above negative electrode mixture was filled into the inside of the separator 3 to obtain the negative electrode 4. At this time, the amount of water in the battery system was 0.256 g per 1 g of the positive electrode active material and 0.633 g per 1 g of the zinc alloy powder contained in the negative electrode.

After filling the power generating element, the negative electrode current collector rod 5 made of brass whose surface is tin-plated and combined with the nylon 6 sealing body 6 is inserted into the central portion of the negative electrode 4, and the open end portion of the outer can 1 is inserted. The AA alkaline battery shown in FIG. 2 was produced by caulking from the outside of 1a by a spinning method. Here, as the negative electrode current collector rod 5, a negative electrode terminal plate 7 made of a nickel-plated steel plate having a thickness of 0.4 mm formed by punching and pressing was attached by welding in advance. An insulating plate 8 was attached between the open end of the outer can 1 and the negative electrode terminal plate 7 to prevent a short circuit. The cylindrical alkaline battery of Example 1 was manufactured as described above.

(Example 2)-(Example 5)
When producing the negative electrode mixture, the ratios of the granular water-absorbing polymer (crosslinked granular sodium polyacrylate) and the thickener (polyacrylic acid) to 100 parts by mass of the zinc alloy powder are shown in Table 1 below. An alkaline battery was produced in the same manner as in Example 1 except that the above was changed to.

(Comparative Example 1)
When producing the negative electrode mixture, except that the ratio of the granular water-absorbing polymer was 0.61 part by mass and the ratio of the thickener was 0.54 part by mass for adjusting the viscosity of the mixture, relative to 100 parts by mass of the zinc alloy powder. An alkaline battery was prepared in the same manner as in Example 1.

(Comparative example 2)
An alkaline battery was produced in the same manner as in Example 1 except that the ratio of the granular water-absorbing polymer to 1.2 parts by mass of the zinc alloy powder was changed to 1.21 parts by mass when preparing the negative electrode mixture.

Table 1 shows the proportions of the granular water-absorbing polymer and the thickener in the negative electrode mixture in the alkaline batteries of Examples 1 to 5 and Comparative Examples 1 and 2.

(Comparative example 3)
As for the zinc alloy powder as the negative electrode active material, the ratio of the powder that passed through the 50-mesh sieve was 99 mass% of the whole powder, and the ratio of the powder that passed through the 200-mesh sieve was 25 mass of the whole powder. An alkaline battery was produced in the same manner as in Example 1 except that the content was changed to%.

(Comparative Example 4)
The zinc alloy powder, which is the negative electrode active material, passed through a 50-mesh sieve in a proportion of 95% by mass of the whole powder, and the proportion of powder passing through a 200-mesh sieve in the whole powder was 10. An alkaline battery was produced in the same manner as in Example 1 except that the content was changed to 5% by mass.

(Comparative example 5)
An alkaline battery was produced in the same manner as in Example 1 except that the zinc alloy powder as the negative electrode active material was changed to one having an Al content of 0.05 mass% (500 ppm).

(Comparative example 6)
An alkaline battery was produced in the same manner as in Example 1 except that the zinc alloy powder as the negative electrode active material was changed to one having a Bi content of 0.05 mass% (500 ppm).

(Comparative Example 7)
An alkaline battery was produced in the same manner as in Example 1 except that the zinc alloy powder as the negative electrode active material was changed to one having an In content of 0.07 mass% (700 ppm).

(Comparative Example 8)
An alkaline battery was produced in the same manner as in Example 1 except that the zinc alloy powder as the negative electrode active material was changed to one having a Mg content of 0.005 mass% (50 ppm).

<Measurement of standard capacity of battery>
The alkaline batteries of Examples 1 to 5 and Comparative Examples 1 to 8 were discharged at a current value of 50 mA until the battery voltage dropped to 0.9 V, and the standard capacity of each battery was evaluated.

<Measurement of medium load discharge characteristics>
The alkaline-batteries of Examples 1 to 5 and Comparative Examples 1 to 8 were connected to a discharge resistance of 3.9Ω, discharged at 20° C. for 1 hour, and then discharged for 23 hours. The total discharge time until the voltage dropped to 0.9 V was measured.

For each of the batteries of Examples and Comparative Examples, the above-mentioned measurement was carried out for each of the five batteries, and the average load discharge characteristics of each battery were evaluated from the average value.

<Measurement of gas generation during over-discharge>
The alkaline batteries of Examples 1 to 5 and Comparative Examples 1 to 8 were connected to a discharge resistance of 10Ω and discharged at 20° C. for 48 hours to be in an overdischarged state. After the discharge was completed, the battery was kept at 20° C. for 120 hours, then the battery was decomposed in water, and the gas in the battery was collected by the water displacement method, and the volume was measured.

Five gas samples were measured for each of the batteries of Examples and Comparative Examples, and the average value was used as the gas generation amount during overdischarge of each battery.

Table 2 shows the relative values of the above-mentioned measurement results when the value of the alkaline battery of Example 1 was set to 100.

As shown in Table 2, in the alkaline battery of the present invention, the content of Al, Bi, In and Mg which are the additive elements of the zinc alloy powder which is the negative electrode active material is set to a suitable value, and the content of fine particles and coarse particles is small. Decrease the proportion of particles, a granular water-absorbing polymer that swells by absorbing the water of the electrolytic solution, by containing in the negative electrode at a constant ratio to the zinc alloy powder, good medium-load discharge characteristics, It was possible to use an alkaline battery in which the amount of gas generated in the battery during overdischarge was small.

1 Outer can 2 Positive electrode 3 Separator 4 Negative electrode 5 Negative electrode current collector rod 6 Sealing body made of resin 7 Negative electrode terminal plate 8 Insulating plate 9 Metal washer 63 Explosion-proof thin-walled part

Claims (6)

An alkaline battery having a negative electrode containing zinc alloy powder, a granular water-absorbing polymer, and an alkaline electrolyte, a positive electrode containing a positive electrode active material, and a separator,
The zinc alloy powder contains 0.005 to 0.015% by mass of Al, 0.005 to 0.015% by mass of Bi, 0.02 to 0.04% by mass of In, and 0.0001 to 0 of Mg. 0.003 mass% each,
In the zinc alloy powder, the proportion of the powder that passes through the 50-mesh sieve is 98% by mass or more of the whole zinc alloy powder, and the proportion of the powder that passes through the 200-mesh sieve is in the entire zinc alloy powder. 15% by mass or less,
The alkaline battery in which the content of the granular water-absorbing polymer in the negative electrode is 0.75 to 1.1 parts by mass with respect to 100 parts by mass of the zinc alloy powder. The negative electrode further contains a thickener,
The alkaline battery according to claim 1, wherein the content of the thickener is 0.15 to 0.35 parts by mass with respect to 100 parts by mass of the zinc alloy powder. The negative electrode further contains a thickener,
The alkaline battery according to claim 1 or 2, wherein the total content of the granular water-absorbing polymer and the thickener is 0.95 to 1.35 parts by mass with respect to 100 parts by mass of the zinc alloy powder. The alkaline battery according to claim 1, wherein the zinc alloy powder has an average particle diameter of 120 μm or more and 200 μm or less. The alkaline battery according to claim 1, wherein the alkaline electrolyte is an aqueous solution containing potassium hydroxide in a concentration of 33% by mass or more and 38% by mass or less. The alkaline battery according to claim 1, wherein the positive electrode active material has a BET specific surface area of 20 m ² /g or more and 40 m ² /g or less.

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