JP2018037359A - Alkali battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an alkali battery with good intermediate load discharge characteristics, which is small in gas generation amount in the battery when overdischarged.SOLUTION: An alkali battery comprises: a negative electrode including zinc alloy powder, a granular absorbent polymer, and an alkali electrolytic solution; a positive electrode; and a separator. In the alkali battery, the zinc alloy powder includes Al of 0.005-0.015 mass%, Bi of 0.005-0.015 mass%, In of 0.02-0.04 mass%, and Mg of 0.0001-0.003 mass%; the percentage of powder passing through a sieve of 50 mesh is 98 mass% or more to a total mass of the zinc alloy powder, and the percentage of powder passing through a sieve of 200 mesh is 15 mass% or less to the total mass of the zinc alloy powder; and the content of the granular absorbent polymer in the negative electrode is 0.75-1.1 pts.mass to 100 pts.mass of the zinc alloy powder.SELECTED DRAWING: None

Description

  The present invention relates to an alkaline battery having good medium load discharge characteristics and a small amount of gas generation 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 depending on its use. Until now, development has been mainly promoted for applications that require a relatively large current, such as digital cameras, cameras with flash, mobile TVs, and emergency chargers.

  For example, in Patent Document 1, the water content of any one of the positive electrode mixture, the positive electrode pellet, or the positive electrode is measured, and the amount of the alkaline electrolyte injected is determined according to the water content. It has been proposed to produce an alkaline battery that is excellent in heavy load discharge characteristics.

In Patent Document 2, the zinc alloy powder contains 100 ppm or more of Al, and the water content in the battery system is 0.250 to 0.300 g per 1 g of the positive electrode active material (or 0.6 per g of zinc alloy powder). To 0.7 g), it is proposed to improve the moisture utilization efficiency at the time of battery discharge, to have excellent heavy load discharge characteristics, and to provide a battery in which gas generation at the time of overdischarge is suppressed. ing.

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

JP 2013-45619 A JP 2010-118285 A Japanese Patent Laid-Open No. 10-50303

  However, recently, the percentage of alkaline batteries used in devices that require a large current as described above has decreased, and instead, in devices that require a relatively small current, such as LED lights and health appliances. The use is increasing, which makes it necessary to study battery designs that are superior in discharge characteristics at medium loads, unlike conventional battery designs that are optimized for heavy load applications.

  Moreover, in order to further improve the reliability of the battery, for example, suppression of gas generation in the battery during overdischarge has been continuously demanded.

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

The alkaline battery of the present invention that has achieved the above object is an alkaline battery having a negative electrode, a positive electrode, and a separator containing a zinc alloy powder, a granular water-absorbing polymer, and an alkaline electrolyte, wherein the zinc alloy powder is 0.005 to 0.015 mass% for Al, 0.005 to 0.015 mass% for Bi, 0.02 to 0.04 mass% for In, and 0.0001 to 0.003 mass% for Mg, respectively. And the zinc alloy powder contains 98 mass% or more of the powder passing through the 50 mesh sieve and the ratio of the powder passing through the 200 mesh sieve is the zinc alloy. 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. To.

  According to the present invention, it is possible to provide an alkaline battery having good medium load discharge characteristics and a small amount of gas generation 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 conventional alkaline batteries, in order to improve the heavy load discharge characteristics, the amount of water is studied 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 as the active material is reduced, and the reaction area is reduced. In order to obtain the target characteristics by increasing the value, measures have been taken.

  On the other hand, as the discharge progresses, the inventors have reduced the utilization rate of the active material of the negative electrode, resulting in an active material that does not contribute to the discharge reaction due to a decrease in moisture in the negative electrode. I noticed that it contributed to the deterioration of the characteristics. In view of this, the present inventors have re-examined the design of the battery so as to maintain the necessary moisture in the negative electrode even when the discharge proceeds in order to improve the medium load discharge characteristics.

  However, increasing the amount of electrolyte in the entire battery so that the amount of water contained in the negative electrode increases will increase the possibility of battery leakage unless the positive or negative electrode charge is reduced. End up.

  On the other hand, if the amount of water contained in the negative electrode is increased by changing the distribution of the electrolyte between the positive electrode and the negative electrode without increasing the total amount of the electrolyte in the battery, the water required for the reaction of the positive electrode is insufficient. As a result, the reaction efficiency of the positive electrode is lowered and the discharge capacity is reduced.

As a result of studying a battery configuration that can improve the utilization rate of the negative electrode active material without causing the above-described problems, the present inventors have found that, in the zinc alloy powder that is the negative electrode active material, Adjusting the content and reducing the ratio of fine particles and coarse particles, and maintaining a certain amount of water in the negative electrode even when the discharge has progressed, and supplying water necessary for the reaction to the negative electrode active material Thus, the granular water-absorbing polymer that swells by absorbing the moisture of the electrolyte solution is contained in the negative electrode at a constant ratio with respect to 100 parts by mass of the zinc alloy powder, so that the above-mentioned purpose can be achieved to some extent. I found 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 In a composition containing 0.02 to 0.04 mass% (200 to 400 ppm) and 0.0001 to 0.003 mass% (1 to 30 ppm) of Mg. Al is preferably 0.007 to 0.013% by mass, Bi is preferably 0.007 to 0.013% by mass, and In is 0.025 to 0.035% by mass. It is preferable that Mg is 0.0003 to 0.002% by mass.

If the amount of the additive element is too small, the effect of the present invention will be insufficient. If the amount is too large, the degree of segregation will increase, causing the discharge characteristics of the battery to deteriorate and gas generation to be promoted.

  The zinc alloy related to the zinc alloy powder typically contains other alloy elements such as Ca as long as the portion other than the alloy elements is Zn and inevitable impurities, but does not impair the effects of the present invention. You may do it.

In the zinc alloy powder used in the negative electrode of the present invention, the proportion of the powder passing through the 50 mesh sieve is 98 mass% or more, preferably 98.5 mass% or more, more preferably, of the entire zinc alloy powder. It shall be 99 mass% or more. That is, the particle size of the zinc alloy powder is adjusted so that substantially the entire amount of the zinc alloy powder passes through the 50 mesh sieve. On the other hand, the ratio of the powder passing through the 200 mesh sieve is 15% by mass or less, preferably 12% by mass or less, more preferably 9% by mass or less. That is, the particle size distribution is adjusted so that the particle size of most zinc alloy powder exists between 50 mesh and 200 mesh.

Note that 50 mesh corresponds to a sieve opening of 300 μm, and 200 mesh corresponds to a sieve opening of 75 μm.

Thereby, the discharge reaction in the negative electrode easily proceeds uniformly, and it becomes possible to efficiently discharge with a smaller water content. In addition, since the variation in the discharge depth of each zinc alloy powder is reduced, it is possible to prevent the generation of a powder that tends to generate gas because the discharge does not proceed more easily than other powders. It is also possible to suppress the amount of gas generated in the battery.

  Here, the granular water-absorbing polymer that swells by absorbing moisture is 0.75 parts by mass or more, preferably 0.8 parts by mass or more, more preferably 0.8 parts by mass or more with respect to 100 parts by mass of the zinc alloy powder in the negative electrode. By containing 85 parts by mass or more, the granular water-absorbing polymer can hold an electrolytic solution (water) necessary for discharge. Therefore, even when the discharge progresses and the flowable electrolyte in the negative electrode decreases and the distribution of the electrolyte tends to be biased, the electrolyte retained in 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, and 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 high, the electrolytic solution is retained in the granular water-absorbing polymer more than necessary, and the reaction resistance of the negative electrode increases due to the lack of flowable electrolytic solution. The content of the granular water-absorbing polymer in the negative electrode is reduced because the filling amount of the alloy powder decreases or the fluidity of the gel negative electrode mixture described later decreases and the productivity deteriorates. 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 with respect to 100 parts by mass.

  In addition, the content rate in the negative electrode of the said granular water absorption polymer means the ratio in the dry state before absorbing electrolyte solution.

  In addition, in the process where zinc oxide, which is a reactant, is generated and diffuses as ions accompanying the discharge of the negative electrode, a part of it remains on the surface of the zinc alloy, hindering the discharge reaction and reducing the resistance of the negative electrode. It is known that it causes an increase in the negative electrode utilization rate. The present inventors consider 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 perform further studies on 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. It was ascertained that deterioration of discharge characteristics due to zinc deposition can be suppressed. In the alkaline electrolyte contained in the negative electrode, the potassium hydroxide concentration increases with the progress of the discharge reaction, and the concentration of the alkaline electrolyte used to form the positive electrode mixture described later is the concentration of the alkaline electrolyte contained in the negative electrode. If it is higher, the concentration gradually increases after the battery is assembled. However, at least during battery assembly, in order to improve ion conductivity, the concentration of potassium hydroxide in the alkaline electrolyte contained in the negative electrode is preferably 38% by mass or less, and 36.5 It is more preferable to set it as mass% or less, and it is most preferable to set it as 35 mass% or less.

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

<Negative electrode>
For the negative electrode according to the alkaline battery of the present invention, a gelled negative electrode mixture (gelled negative electrode) having the zinc alloy powder, the granular water-absorbing polymer, and an alkaline electrolyte is used.

  As described above, the zinc alloy powder has a particle size adjusted so that the ratio of coarse particles and fine particles is reduced, but in order to make the effect of the present invention more excellent, the average particle size is: It is preferably 120 μm or more, more preferably 150 μm or more, and on the other hand, it is preferably 200 μm or less, and more preferably 185 μm or less.

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

  By using a granular polymer having excellent liquid retention, the water-absorbing polymer can sufficiently retain moisture necessary for the reaction of the negative electrode active material.

  The average particle diameter 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 so that the zinc alloy powder can be easily held in the negative electrode. Most preferred. On the other hand, in order not to inhibit 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 contained in the negative electrode is not particularly limited, and is the same as the electrolyte used in conventionally known alkaline batteries and alkaline storage batteries (for example, potassium hydroxide, lithium hydroxide, water) Alkaline aqueous solutions such as aqueous solutions of alkali metal hydroxides such as sodium oxide) can be used, but from the viewpoint of facilitating diffusion of the reaction product of the negative electrode described above, an aqueous solution containing at least potassium hydroxide, An aqueous solution having a concentration of 33% by mass or more is used.

  Moreover, the negative electrode according to the alkaline battery of the present invention can contain various additives as they are or 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 the generation of discharge products on the surface of the zinc alloy powder and the 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.

Moreover, the effect which suppresses the gas generation | occurrence | production by corrosion of zinc alloy powder can be anticipated by making a negative electrode contain a zinc compound. As the zinc compound, for example, a compound such as zinc oxide, zinc silicate, zinc titanate, zinc molybdate can be used, and it is preferably contained in a state dissolved in an alkaline electrolyte, particularly zinc oxide. Are preferably used.

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

  The negative electrode according to the alkaline battery of the present invention preferably contains a thickener that is soluble in an alkaline electrolyte in order to make the viscosity when gelled into a suitable range. Examples of the thickener include celluloses such as poly (meth) acrylic acid, poly (meth) acrylate, carboxymethylcellulose, methylcellulose, hydroxypropylcellulose or salts thereof, and crosslinked branched poly (meth). Acrylic acid and cross-linked branched poly (meth) acrylate are preferably used. Examples of the salt of the poly (meth) acrylate and the cellulose include alkali metal salts and ammonium salts, and sodium salts and potassium salts are preferably used.

  In order to sufficiently increase the viscosity of the negative electrode mixture, the content of the thickener in the negative electrode is preferably 0.15 parts by mass or more with respect to 100 parts by mass of the zinc alloy powder. The amount is more preferably at least part by mass, and on the other hand, in order to impart a certain degree of fluidity to the negative electrode mixture, it is preferably at most 0.35 mass, more preferably at most 0.3 mass part.

  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. More preferably, it is 1.05 parts by mass or more, more preferably 1.3 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. 70 mass% or less is more preferable.

<Positive electrode>
The positive electrode according to the alkaline battery of the present invention includes, for example, a positive electrode active material, a conductive additive, and further an alkaline electrolyte and a binder for molding to form a positive electrode mixture. 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, and manganese dioxide is preferably used.

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

On the other hand, it is desirable to improve the characteristics on the positive electrode side in accordance with the improvement of 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. Thereby, the filling amount of a positive electrode active material can be increased, the capacity | capacitance of a positive electrode can be enlarged, and it can respond to the characteristic improvement of a negative electrode.

  Note that the BET specific surface area of the positive electrode active material here is a specific surface area of the surface of the active material and the micropores, which is a surface area measured and calculated using the BET equation, which is a theoretical formula for multi-layer adsorption. . Specifically, it is a value obtained as a BET specific surface area by using a specific surface area measuring apparatus (for example, Macsorb HM model-1201 manufactured by Mounttech) by a nitrogen adsorption method.

  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 increase the reaction area to a certain level or more and increase 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.

  For example, graphite, ketjen black, acetylene black, or the like can be used as the conductive additive related to the positive electrode. The amount of the conductive auxiliary agent in the positive electrode mixture is preferably 3 parts by mass or more, more preferably 4.5 parts by mass or more with respect to 100 parts by mass of the positive electrode active material, from the viewpoint of improving conductivity. , 6 parts by mass or more is most preferable. On the other hand, in order to ensure the capacity of the positive electrode, it is preferably 10 parts by mass or less, more preferably 8.5 parts by mass or less, and more preferably 7 parts by mass or less with respect to 100 parts by mass of the positive electrode active material. Most preferred.

  As the binder for the positive electrode, for example, polytetrafluoroethylene, polyvinylidene fluoride, styrene butadiene rubber, or the like can be used. The amount of the 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 an alkali metal hydroxide such as potassium hydroxide, sodium hydroxide, lithium hydroxide or the like is dissolved in water, or a zinc oxide added thereto. Although used, a potassium hydroxide aqueous solution is more preferable from the viewpoint of enhancing the discharge characteristics of the battery. For example, in the case of potassium hydroxide, the concentration of the alkali metal hydroxide in the electrolytic solution is preferably 40 to 60% by mass. When zinc oxide is used, the concentration is 1.0 to It is preferable that it is 4.0 mass%.

  In addition, the average particle diameter used in the present invention is a value expressed as a volume average particle diameter (D50) obtained by measurement of particle size distribution using a particle size distribution meter.

<Electrolyte>
In addition to the use for the positive electrode and the negative electrode, as the alkaline electrolyte for injecting into the battery, for example, the alkaline electrolyte for absorbing the separator, as in the electrolyte for the positive and negative electrodes, An alkaline aqueous solution composed of an aqueous solution of an alkali metal hydroxide such as potassium, sodium hydroxide or lithium hydroxide, or a solution in which zinc oxide is added thereto can be used, but it is the same as the alkaline electrolyte used for the negative electrode. A configuration is preferable.

<Separator>
The separator for the alkaline battery of the present invention is not particularly limited. For example, a nonwoven fabric mainly composed of vinylon and rayon, a vinylon / rayon nonwoven fabric (vinylon / rayon mixed paper), a polyamide nonwoven fabric, a polyolefin / rayon nonwoven fabric, a vinylon paper, a vinylon. -Linter pulp paper, vinylon mercerized pulp paper, etc. can be used. In addition, a separator in which 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 as a separator. .

<Moisture content 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 apparent from the above formula (1), in an alkaline battery, water is consumed during discharge, and therefore, from the viewpoint of the discharge reaction, it is desirable that a certain amount or more of moisture exists in the battery. In the alkaline battery, the amount of water in the battery system is preferably 0.23 g or more, 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, more preferably 0.6 g or more, per 1 g of the zinc alloy powder of the negative electrode.

  On the other hand, in order to easily suppress the gas generation in the battery (especially gas generation in the battery at the time of overdischarge), it is desirable to reduce the excess water regardless of the reaction as much as possible. Is preferably 0.27 g or less, more preferably 0.26 g or less, per 1 g of the positive electrode active material. Alternatively, the water content in the battery system is preferably 0.675 g or less, more preferably 0.66 g or less, per 1 g of the zinc alloy powder of the negative electrode.

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

<Structure of alkaline battery and other components>
In the alkaline battery of the present invention, the shape thereof is not particularly limited, and 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 cross-sectional view showing an example of the alkaline battery of the present invention. The alkaline battery shown in FIG. 1 has a positive electrode 2 (positive electrode mixture molded body) formed in a ring shape in a metal outer casing 1 (Ni-plated iron, stainless steel, etc.). A cup-shaped separator 3 is disposed on the inner side, and an alkaline electrolyte (not shown) is injected from the inner side of the separator 3. Furthermore, the negative electrode 4 (gel-like negative electrode mixture) containing zinc alloy powder is filled inside the separator 3. 1b in the outer can 1 is a positive electrode terminal. A metal negative electrode terminal plate 7 is disposed on the opening end 1a of the outer can 1 through an outer peripheral edge 62 of the resin sealing body 6. The open end 1a is folded 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 at the central portion 61 of the sealing body 6. The inserted through hole 64 is inserted into the negative electrode 4. Further, a metal washer 9 (disc-shaped metal plate) is disposed as a supporting means for preventing the negative electrode terminal plate 7 from being deformed during 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 a short circuit, the thin portion 63 of the sealing body 6 is preferentially cleaved, and the gas moves to the metal washer 9 side from the generated fissure. The metal washer 9 and the negative electrode terminal plate 7 are provided with gas vent holes (not shown), and the gas in the battery is discharged out of the battery through these gas vent holes. Examples of the resin constituting the resin sealing body 6 include nylon 66 and the like.

  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 functions as those in FIG. In FIG. 2, 8 is an insulating plate for insulating the outer can 1 and the negative electrode terminal plate 7, and 20 is a body portion that houses 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 as in the battery of FIG. 2 and using the negative electrode terminal plate 7 as a support means for supporting the sealing body 6 from the inside, the volume occupied by the sealing portion 10 can be reduced and the power generation element can be reduced. The volume of the trunk 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.

Example 1
<Formation of positive electrode mixture>
Manganese dioxide containing 1.6% by weight of water (average particle size: 36.5 μm, BET specific surface area: 31 m ² / g), graphite, zinc oxide, polytetrafluoroethylene powder and alkaline electrolyte for preparing 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. In addition, the potassium hydroxide concentration of the electrolyte solution contained in the positive electrode mixture was 45.4% by mass in consideration of the water content of manganese dioxide.

<Formation of negative electrode mixture>
A zinc alloy containing 0.01% by mass (100 ppm) of Al, 0.01% by mass (100 ppm) of Bi, 0.03% by mass (300 ppm) of In, and 0.0005% by mass (5 ppm) of Mg. Powder, a crosslinked product of granular sodium polyacrylate having an average particle size of 500 μm, an alkaline electrolyte for preparing polyacrylic acid and a negative electrode mixture (34% by mass of potassium hydroxide, and 2.% of zinc oxide). 9 mass% aqueous solution) 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 has an average particle size of 170 μm, the proportion of the powder that passed through the 50 mesh sieve is 98.7% by mass of the whole powder, and the proportion of the powder that passed through the 200 mesh sieve However, it was 11 mass% of the whole powder.

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

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

Next, a nonwoven fabric made of acetalized vinylon having a thickness of 100 μm and a basis weight of 30 g / m ² and tencel is overlapped in a cylinder, wound into a cylindrical shape, the bottom portion is bent, this portion is heat-sealed, and one end is closed The cup-shaped separator 3 thus obtained was obtained. This separator 3 is loaded inside the positive electrode 1 inserted into the outer can 1 and is contained in an alkaline electrolyte (34% by mass of potassium hydroxide and 2.9% by mass of zinc oxide) for absorbing the separator. 1.33 g was poured into the separator, and 5.74 g of the negative electrode mixture was filled into the separator 3 to obtain a negative electrode 4. At this time, the water content 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 of the negative electrode.

  After filling the power generation element, the negative electrode current collector rod 5, which has a tin-plated brass surface and is combined with a nylon 66 sealing body 6, is inserted into the central portion of the negative electrode 4, and the open end of the outer can 1 The AA alkaline battery shown in FIG. 2 was produced by caulking from the outside of 1a by a spinning method. Here, the negative electrode current collecting rod 5 used was previously attached by welding to a negative electrode terminal plate 7 made of nickel-plated steel plate having a thickness of 0.4 mm formed by stamping and pressing. An insulating plate 8 was mounted 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 produced as described above.

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

(Comparative Example 1)
When preparing the negative electrode mixture, the proportion of the granular water-absorbing polymer with respect to 100 parts by mass of the zinc alloy powder is 0.61 part by mass, and the proportion of the thickener is 0.54 parts by mass for adjusting the viscosity of the mixture. Produced an alkaline battery 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 proportion of the granular water-absorbing polymer with respect to 100 parts by mass of the zinc alloy powder was 1.21 parts by mass when producing 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)
In the zinc alloy powder as the negative electrode active material, the proportion of the powder that passed through the 50 mesh sieve was 99 mass% of the total powder, and the proportion 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 that of%.

(Comparative Example 4)
In the zinc alloy powder as the negative electrode active material, the proportion of the powder that passed through the 50 mesh sieve was 95% by mass, and the proportion of the powder that passed through the 200 mesh sieve 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 fabricated 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, which was 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, which was the negative electrode active material, was changed to one having an In content of 0.07% by mass (700 ppm).

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

<Measurement of standard battery capacity>
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>
For the alkaline batteries of Examples 1 to 5 and Comparative Examples 1 to 8, a discharge resistance of 3.9Ω was connected, discharged at 20 ° C. for 1 hour, and then rested for 23 hours. The total discharge time until the voltage decreased to 0.9 V was measured.

About each battery of an Example and a comparative example, the said measurement was performed by 5 each, and the medium load discharge characteristic of each battery was evaluated from the average value.

<Measurement of gas generation during overdischarge>
A 10 Ω discharge resistor was connected to the alkaline batteries of Examples 1 to 5 and Comparative Examples 1 to 8, and discharged at 20 ° C. for 48 hours to form an overdischarged state. After completion of the discharge, the battery was held at 20 ° C. for 120 hours, then the battery was disassembled in water, and the gas in the battery was collected by the water displacement method and its volume was measured.

About each battery of an Example and a comparative example, the said gas amount measurement was performed by each 5 pieces, and the average value was made into the gas generation amount at the time of the overdischarge of each battery.

  Table 2 shows the relative values when the value of the alkaline battery of Example 1 is set to 100 for each measurement result.

  As shown in Table 2, in the alkaline battery of the present invention, the content of the additive elements Al, Bi, In, and Mg in the zinc alloy powder that is the negative electrode active material is set to a suitable value, and fine particles and coarse particles By reducing the proportion of particles and incorporating a granular water-absorbing polymer that swells by absorbing moisture in the electrolyte solution into the negative electrode at a certain ratio with respect to the zinc alloy powder, the medium-load discharge characteristics are good, An alkaline battery with a small amount of gas generation in the battery during overdischarge could be obtained.

DESCRIPTION OF SYMBOLS 1 Exterior can 2 Positive electrode 3 Separator 4 Negative electrode 5 Negative electrode current collecting rod 6 Sealing body made of resin 7 Negative electrode terminal plate 8 Insulating plate 9 Metal washer 63 Thin-walled portion for explosion protection

Claims (6)

An alkaline battery having a negative electrode containing a 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 comprises 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 of Mg. 0.003 mass% each,
In the zinc alloy powder, the proportion of the powder passing through the 50 mesh sieve is 98% by mass or more of the entire zinc alloy powder, and the proportion of the powder passing through the 200 mesh sieve is based on 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 a 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 size 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 at 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.

Images