JP5172181B2 - Zinc alkaline battery - Google Patents

Description

  The present invention relates to a zinc alkaline battery using a zinc alloy as a negative electrode active material, an alkaline aqueous solution as an electrolytic solution, and manganese dioxide or nickel oxyhydroxide as a positive electrode active material.

Zinc alkaline batteries represented by alkaline manganese batteries are widely used as power sources for various devices because they are versatile and inexpensive. In such a zinc alkaline battery, an irregularly shaped zinc powder produced by a gas atomizing method or the like is used as a negative electrode active material.
However, when zinc powder corrodes in an alkaline electrolyte, hydrogen gas is generated, and the internal pressure of the battery may increase or liquid leakage may occur. For this reason, it is important to suppress the corrosion of the zinc powder and improve the reliability of the zinc alkaline battery.

  For this, for example, a method is used in which mercury is added to the negative electrode to amalgamate the surface of the zinc powder, thereby increasing the hydrogen overvoltage and improving the corrosion resistance. However, due to the increasing awareness of the environment, there has been a demand for dehydration mainly in alkaline manganese dry batteries from around 1980 to 1990. For example, the following methods (A) to (C) include the following methods. At present, zinc-alkaline batteries using various combinations of these have been studied.

(A) A zinc alloy powder having excellent corrosion resistance, including aluminum, bismuth, indium or the like, is used as the negative electrode active material (for example, Patent Document 1).
(B) An inorganic anticorrosive agent such as indium hydroxide, bismuth hydroxide, indium sulfide, or an alkali metal sulfide is added to the negative electrode (for example, Patent Documents 2 to 4).
(C) An organic anticorrosive agent such as a surfactant is added to the negative electrode (for example, Patent Document 5).

By the way, in recent years, with the progress of digitalization and high performance of devices, load power required for zinc alkaline batteries such as alkaline manganese dry batteries used as a power source thereof has increased. On the other hand, for example, in Patent Documents 6 and 7, the reactivity is increased by using zinc powder containing a large amount of fine powder having a particle size of 75 μm or less that passes through a 200-mesh sieve as a negative electrode active material, and high load is applied. It has been proposed to improve the discharge characteristics.
JP-A-5-166507 JP-A 48-77332 Japanese Patent No. 2808822 Japanese Patent No. 2754864 Japanese Patent Laid-Open No. 5-266882 Special table 2001-512284 gazette JP 2002-270164 A

  However, when a plurality of batteries using zinc fine powder as the negative electrode active material are connected in series and constant resistance discharge is performed, among the plurality of batteries, a battery having a small capacity is likely to be overdischarged, and further overdischarge is caused. As the battery progresses, the battery is reversely charged, and the polarity is reversed by at least one of the positive electrode and the negative electrode, which may cause significant leakage. Specifically, when a plurality of alkaline manganese dry batteries are connected in series and used as a power source for toys, lights, etc., and left in a connected state after use, there is a possibility of leakage. And this leakage may damage the equipment.

  The gas generation reaction (water decomposition reaction) when the positive electrode and the negative electrode are reversed is represented by the following equations, respectively. When the amount of electricity supplied to the positive electrode and the negative electrode is the same, the amount of hydrogen gas generated by the reversal of the positive electrode is twice the amount of oxygen gas generated by the reversal of the negative electrode. For this reason, during overdischarge, it is considered that the polarity of the positive electrode is greater than that of the negative electrode, and the amount of gas generated is larger, the battery internal pressure is increased, and liquid leakage is likely to occur.

(Reaction when the positive electrode is reversed) 2H ₂ O + 2e ⁻ → H ₂ + 2OH ⁻
(Reaction when the negative electrode is reversed) 4OH ⁻ → O ₂ + 2H ₂ O + 4e ⁻
Therefore, in order to solve the above-described conventional problems, the present invention suppresses the occurrence of liquid leakage due to a significant increase in battery internal pressure accompanying gas generation during overdischarge even when a fine powder negative electrode active material is used. An object of the present invention is to provide a zinc-alkaline battery having excellent high-load discharge characteristics and high reliability.

  A zinc alkaline battery according to the present invention includes a negative electrode including a zinc alloy powder containing 20 to 50% by weight of a fine powder having a particle size of 75 μm or less, a positive electrode, a separator disposed between the negative electrode and the positive electrode, and an electrolytic solution. In the constant resistance discharge, the rising time of the negative electrode potential is shorter than the falling time of the positive electrode potential.

As described above, in the constant resistance discharge, the time during which the negative electrode potential rises is shorter than the time during which the positive electrode potential falls, that is, the negative electrode before the positive electrode potential falls at the end of the constant resistance discharge. In the negative electrode capacity-regulated battery in which the potential rises, at least one additive selected from the group consisting of alkali metal sulfides and indium sulfide is added to the negative electrode in an amount of 0.02 to 0.000 per 100 parts by weight of the zinc alloy powder. This can be realized by including 1 part by weight.
The zinc alloy powder contains 0.005 to 0.1% by weight of at least one selected from the group consisting of bismuth and indium, and at least one selected from the group consisting of aluminum and calcium from 0.001 to 0.00. It is preferable to contain 05% by weight.

  According to the present invention, a zinc-alkaline battery excellent in high-load discharge characteristics can be obtained by using a finely divided negative electrode active material. Further, even when a finely divided negative electrode active material is used, it is possible to suppress the occurrence of liquid leakage due to a significant increase in the internal pressure of the battery due to gas generation during overdischarge, and the reliability of the zinc alkaline battery is improved.

The present invention includes a negative electrode including a zinc alloy powder containing 20 to 50% by weight of a fine powder having a particle size of 75 μm or less, a positive electrode, a separator disposed between the negative electrode and the positive electrode, and an electrolytic solution. The negative electrode relates to a zinc-alkaline battery containing at least one additive selected from the group consisting of alkali metal sulfides and indium sulfides in an amount of 0.02 to 0.1 parts by weight per 100 parts by weight of the zinc alloy powder.
By adding an additive to the negative electrode as described above, the time during which the negative electrode potential rises during constant resistance discharge can be made shorter than the time during which the positive electrode potential falls. That is, at the end of the constant resistance discharge, a negative electrode capacity-regulated zinc alkaline battery in which the negative electrode potential rises before the positive electrode potential falls can be obtained.

In this way, by deliberately increasing the polarization of the negative electrode at the end of discharge and increasing the time for the negative electrode potential to rise, due to overdischarge of a battery with a small capacity, which occurs when a plurality of batteries are connected in series, etc. The inversion can be limited to the inversion of only the negative electrode (oxygen generation). For this reason, generation | occurrence | production of a large amount of hydrogen gas by the inversion of a positive electrode is suppressed, the raise of a battery internal pressure is suppressed, and a liquid leak can be suppressed.
The above “time for the negative electrode potential to rise” refers to the time from the start of discharge until the negative electrode potential suddenly increases and reaches a predetermined potential at the end of discharge. In addition, the “time for the positive electrode potential to fall” refers to the time from the start of discharge until the positive electrode potential rapidly decreases and reaches a predetermined potential at the end of discharge.

  For example, in an AA alkaline manganese dry battery (negative electrode theoretical capacity / positive electrode theoretical capacity = 1.16) using a positive electrode containing electrolytic manganese dioxide as a positive electrode active material and a negative electrode containing a zinc alloy as a negative electrode active material, 20 A 10 Ω constant resistance discharge is performed in an atmosphere of ° C. At this time, a hole is formed in a part of the positive electrode case, a salt bridge is arranged between the positive electrode or negative electrode in the battery and the mercury / mercury oxide reference electrode outside the battery, and the positive electrode potential with respect to the mercury / mercury oxide reference electrode and Obtain the negative electrode potential. Note that the negative electrode theoretical capacity refers to the capacity when all of the negative electrode active material contained in the negative electrode is used for the battery reaction. The positive electrode theoretical capacity refers to the capacity when all of the positive electrode active material contained in the positive electrode is used for the battery reaction. Then, the time from when the discharge is started until the negative electrode potential reaches −1.2 V vs. Hg / HgO is measured as the time when the negative electrode potential rises. After the discharge is started, the positive electrode potential is −0. Measure the time to reach 6V vs. Hg / HgO as the time for the positive electrode potential to fall. When the negative electrode potential exceeds −1.2 V vs. Hg / HgO, oxygen gas is generated. Hydrogen gas is generated when the positive electrode potential is less than −0.6 V vs. Hg / HgO.

As described above, when an alkali metal sulfide is added to the negative electrode, the negative electrode is obtained at the end of the constant resistance discharge without impairing the excellent high-load discharge characteristics obtained when a zinc alloy powder containing a large amount of fine powder is used. It has been found that the potential rise is accelerated and leakage during overdischarge can be suppressed.
Examples of the alkali metal sulfide include potassium sulfide and sodium sulfide. Alkali metal sulfides dissolve in an alkaline electrolyte and exist as alkali metal ions and sulfide ions in the alkaline electrolyte. The generated sulfide ions react with zinc in the presence of zinc to form a relatively inert zinc sulfide coating on the zinc surface. When the thickness of the zinc sulfide coating is appropriate, the discharge reaction of zinc is not inhibited in the potential region during discharge in a normal negative electrode. The detailed mechanism is not clear, but among the zinc powders, the negative electrode potential suddenly rises at the end of the discharge due to the effect of the zinc sulfide film formed on the surface of the fine powder, and the discharge is quickly stopped. Can do.

If the content of the alkali metal sulfide in the negative electrode is less than 0.02 parts by weight per 100 parts by weight of the zinc alloy powder, the effect of accelerating the rise of the negative electrode potential at the end of discharge cannot be obtained sufficiently. Further, if the content of the alkali metal sulfide in the negative electrode exceeds 0.1 parts by weight per 100 parts by weight of the zinc alloy powder, the zinc sulfide coating thickness formed on the surface of the zinc particles becomes too thick, Load discharge characteristics are degraded.
Further, when the negative electrode additive is an alkali metal sulfide, an effect of suppressing corrosion of the negative electrode when the initial battery or the partially discharged battery is stored at a high temperature or the like can be obtained.
More preferably, the content of the alkali metal sulfide in the negative electrode is 0.02 to 0.06 parts by weight per 100 parts by weight of the zinc alloy.

  Even when the additive of the negative electrode is indium sulfide, the same effect as that of the alkali metal sulfide can be obtained. When indium sulfide coexists with zinc in an alkaline electrolyte, it is electrodeposited in the form of metallic indium scattered on the zinc surface, and at the same time, a zinc sulfide film is formed on the remaining zinc surface. At this time, if the thickness of the zinc sulfide film to be formed is appropriate, the discharge reaction of zinc is not inhibited in the potential region during discharge in a normal negative electrode. Then, the negative electrode potential rises rapidly at the end of discharge, and the discharge can be stopped quickly.

When the content of indium sulfide in the negative electrode is less than 0.02 parts by weight per 100 parts by weight of the zinc alloy powder, the effect of speeding up the negative electrode potential at the end of discharge cannot be sufficiently obtained. Also, if the content of indium sulfide in the negative electrode exceeds 0.1 parts by weight per 100 parts by weight of the zinc alloy powder, the coating thickness of zinc sulfide formed on the surface of the zinc particles becomes too thick, resulting in high load discharge characteristics. Decreases.
In addition, when indium sulfide is added to the negative electrode, an effect of suppressing corrosion of the negative electrode when the initial battery or the partially discharged battery is stored at a high temperature or the like can be obtained. Furthermore, when indium sulfide is added to the negative electrode, the effect of joining zinc particles together by electrodeposition of metallic indium can be obtained, so that the high-load discharge characteristics are further improved.
More preferably, the content of indium sulfide in the negative electrode is 0.02 to 0.06 parts by weight per 100 parts by weight of the zinc alloy.

  In order to improve the corrosion resistance of the zinc alloy, the zinc alloy contains 0.005 to 0.1% by weight of at least one selected from the group consisting of bismuth and indium, and at least selected from the group consisting of aluminum and calcium. One type is preferably contained in an amount of 0.001 to 0.05% by weight. Zinc alloy powder containing 20-50% by weight of fine powder of 200 mesh or less is more easily corroded by alkaline electrolyte than conventional zinc alloy powder with less fine powder, so it is important to improve the corrosion resistance of the alloy It is.

  The bismuth and indium contained in the zinc alloy are unevenly distributed in the grain boundary portion of the zinc crystal where corrosion is likely to proceed, thereby increasing the hydrogen overvoltage and exhibiting the effect of suppressing the corrosion of zinc. If the total content of bismuth and indium in the zinc alloy is less than 0.005% by weight, a sufficient anticorrosion effect cannot be obtained. When the total content of bismuth and indium in the zinc alloy exceeds 0.1% by weight, the discharge characteristics deteriorate. For this reason, the total content of bismuth and indium in the zinc alloy is preferably 0.005 to 0.1% by weight.

  Aluminum and calcium contained in the zinc alloy are unevenly distributed in the vicinity of the surface of the zinc particles, smooth the surface, and exhibit the effect of suppressing corrosion of zinc. If the total content of aluminum and calcium in the zinc alloy is less than 0.001% by weight, a sufficient anticorrosion effect cannot be obtained. When the total content of aluminum and calcium in the zinc alloy exceeds 0.05% by weight, the discharge characteristics deteriorate. For this reason, the total content of aluminum and calcium in the zinc alloy is preferably 0.001 to 0.05% by weight.

As the negative electrode, for example, a negative electrode active material powder, a gelling agent, an electrolytic solution, and a gelled negative electrode composed of the above additives are used. As the negative electrode active material, for example, the zinc alloy powder having an average particle diameter of 100 to 200 μm is used. For example, sodium polyacrylate is used as the gelling agent.
As a method for adding the additive to the negative electrode, for example, at the time of preparing the negative electrode, the negative electrode active material powder, the gelling agent, and the electrolytic solution are mixed with the additive in advance before the negative electrode active material powder, the gelling agent, and the electrolytic solution are mixed. It is obtained by mixing a substance powder, a gelling agent, and an electrolytic solution containing an additive. By this method, the additive can be easily and uniformly dispersed in the negative electrode.

For the positive electrode, for example, a positive electrode mixture made of a mixture of a positive electrode active material, a conductive material, and an electrolytic solution is used. As the positive electrode active material, manganese dioxide powder or nickel oxyhydroxide powder having an average particle size of 30 to 50 μm is used. These may be used alone or in combination. For the conductive material, for example, graphite powder having an average particle size of 10 to 20 μm is used.
For the separator, for example, a porous sheet made of a composite nonwoven fabric of vinylon and rayon having a thickness of 80 to 150 μm is used. And an electrolyte solution is included in a separator at the time of battery assembly.
For example, an aqueous potassium hydroxide solution having a concentration of about 30 to 40% by weight is used as the electrolytic solution. Further, zinc oxide (for example, about 2% by weight) may be further contained in the potassium hydroxide aqueous solution.

Examples of the present invention will be described in detail below, but the present invention is not limited to these examples.
Example 1
A cylindrical alkaline manganese dry battery (AA) shown in FIG. 1 was produced as the zinc alkaline battery of the present invention by the following procedure. FIG. 1 is a front view of a cross section of a part of an alkaline manganese battery of the present invention.

(1) Production of gelled negative electrode A zinc alloy powder containing 0.005% by weight of Al, 0.02% by weight of Bi, and 0.03% by weight of In was produced by a gas atomization method. Then, classification and particle size adjustment by a sieve, a zinc alloy powder A having a particle size range of 35 to 150 mesh and a fine powder content of 75 μm or less and passing through a 200 mesh sieve is 0 wt%, A zinc alloy powder B having a particle size range of 35 to 300 mesh and a fine powder content of 75 μm or less passing through a 200 mesh sieve and having a particle size of 30% by weight was obtained.

  Next, an additive is added to 100 parts by weight of an aqueous solution containing 36% by weight potassium hydroxide and 2% by weight ZnO, and then 2 parts by weight of sodium polyacrylate is added and mixed to obtain a gel electrolyte. Obtained. Then, the gelled electrolyte solution and the zinc alloy powder were mixed at a weight ratio of 1.0: 1.8 to obtain a gelled negative electrode 6. At this time, with respect to the zinc alloy powder A or B, 12 types of gelled negative electrodes (1) to (12) were obtained by changing the types and amounts of additives as shown in Table 1. In Table 1, the surfactants used in the gelled negative electrodes (4), (5), (10), and (11) include polyoxyethylene alkyl ether compounds represented by the following chemical formula (1) It was used. In addition, the addition amount of Table 1 shows the quantity (weight part) per 100 weight part of zinc alloy powder.

(2) Preparation of positive electrode mixture pellets Electrolytic manganese dioxide powder (average particle size: 40 μm) and graphite powder (average particle size: 12 μm) were mixed at a weight ratio of 94: 6, and an electrolyte solution was added to 100 parts by weight of this mixture. After adding 1 part by weight, the mixture was uniformly stirred and mixed with a mixer to adjust the particle size to a constant particle size. The obtained granular material was pressure-formed into a hollow cylindrical shape to obtain a positive electrode material mixture pellet 3.

(3) Preparation of alkaline manganese dry battery A plurality of positive electrode mixture pellets 3 were inserted into a positive electrode case 1 made of a nickel-plated steel plate and re-pressurized in the positive electrode case 1 to adhere to the inner surface of the positive electrode case 1. . A graphite coating film 2 is formed in advance in the positive electrode case 1. And after inserting the separator 4 and the base paper 5 for insulation inside this positive electrode mixture pellet 3, the electrolyte solution was inject | poured in order to wet the separator 4 and the positive electrode mixture pellet 3. FIG. The separator 4 was a porous sheet made of a composite nonwoven fabric of vinylon and rayon having a thickness of 120 μm. Further, an alkaline aqueous solution containing 2 wt% ZnO and 36 wt% potassium hydroxide was used as the electrolytic solution.

  After the injection, the gelled negative electrode 6 was filled inside the separator 4. Next, a negative electrode current collector 10 integrated with a resin sealing body 7, a bottom plate 8 serving also as a negative electrode terminal, and an insulating washer 9 was inserted into the gelled negative electrode 6. And the opening part of the positive electrode case 1 was sealed by crimping the opening edge part of the positive electrode case 1 on the peripheral part of the bottom plate 8 via the edge part of the sealing body 7. FIG. Next, an outer label 11 was coated on the outer surface of the positive electrode case 1. In this manner, an alkaline manganese battery was produced.

And at the time of the said battery production, alkaline manganese dry batteries (1)-(12) were produced using the gelled negative electrodes (1)-(12), respectively.
The positive electrode active material amount and the negative electrode active material amount were adjusted so that the negative electrode capacity ratio (negative electrode theoretical capacity / positive electrode theoretical capacity) to positive electrode capacity was 1.16.

[Evaluation]
The alkaline manganese dry batteries (1) to (12) produced above were evaluated for the following (I) to (III). The batteries (8) and (9) are examples, and the batteries (1) to (7) and (10) to (12) are comparative examples.

(I) High-load discharge test The initial battery was continuously discharged at a constant power of 1000 mW in a 20 ° C atmosphere, and the time until the battery voltage reached 0.9 V was measured.
(II) Storage test after partial discharge The first battery (20 cells each) was discharged in a 20 ° C. atmosphere at a constant current of 1000 mA for 32 minutes (corresponding to 20% of the positive electrode theoretical capacity), and then the environment at 60 ° C. Stored below for 2 weeks. At this time, the ratio of leaked batteries (leakage rate (%)) was determined.
(III) Overdischarge test Four initial batteries were connected in series, connected to a 40Ω resistor, and left in a 20 ° C. atmosphere for 8 weeks to cause overdischarge. At this time, the presence or absence of liquid leakage was examined. In this case, the leakage occurred mostly in the battery with the smallest capacity among the four batteries connected in series. Here, one set of four batteries connected in series via a resistor was taken as one set, and 10 sets (40 cells) of each were tested to determine the rate of occurrence of liquid leakage (%).
These evaluation results are shown in Table 2.

In the batteries (7) to (12) using the zinc alloy powder B, excellent high load discharge characteristics were obtained as compared with the batteries (1) to (6) using the zinc alloy powder A. This is considered to be because the zinc alloy powder B used in the batteries (7) to (12) contains a large amount of fine powder, so that the contact area with the electrolyte is increased and the efficiency of the discharge reaction is improved. Comparing the batteries (1) to (6) using the zinc alloy powder A, the batteries (1) and (3) using In (OH) ₃ and In ₂ S ₃ as the negative electrode additive are the batteries (2). And the discharge characteristic superior to (4)-(6) was obtained. Further, in the batteries (4) and (5) using a surfactant as an additive, the discharge characteristics were slightly lowered.

Comparing the batteries (7) to (12) using the zinc alloy powder B, the batteries (7) and (9) using In (OH) ₃ and In ₂ S ₃ as the negative electrode additive are the batteries (8). And the discharge characteristic superior to (10)-(12) was obtained. Further, in the batteries (10) and (11) using the surfactant as the additive, the discharge characteristics were slightly deteriorated.
The reason why the discharge characteristics are improved when In (OH) ₃ and In ₂ S ₃ that are indium sulfides are used as the additive is that electrodeposition of metallic indium occurs in the negative electrode, and this metallic indium causes zinc particles to interact with each other. It is conceivable that the current collecting property is improved by bonding. In addition, when a surfactant is used as an additive, the reason why the discharge characteristics are slightly lowered may be that the discharge reaction is hindered due to the high adsorptivity of the surfactant to the zinc alloy.

Moreover, in the battery (12) using the zinc alloy powder B, it was shown that the battery (6) using the zinc alloy powder A is more likely to leak during storage after partial discharge. This is considered to be due to the fact that the zinc alloy powder B contains a large amount of fine powder, so that the corrosion resistance was lowered. On the other hand, even when the zinc alloy powder B was used, in the batteries (7) to (11) using the negative electrode additive, excellent leakage resistance was obtained during storage after partial discharge. Furthermore, in the batteries (8) and (9) of the examples of the present invention using K ₂ S or In ₂ S ₃ as the negative electrode additive, even when the zinc alloy powder B is used, with excellent high load discharge characteristics Excellent leakage resistance was obtained during overdischarge.

In the overdischarge test, there was a battery in which leakage occurred when the zinc alloy powder B was used. Since there is no correlation with the result of the storage test after partial discharge, which has been a problem in the past, leakage during overdischarge can be regarded as a particular problem when using a zinc alloy powder containing a large amount of fine powder. .
In order to clarify the leakage phenomenon during such overdischarge, the first battery (1), (7), (8) and (9) was subjected to 10Ω constant resistance discharge in an atmosphere of 20 ° C. It was. At this time, a hole is provided in a part of the positive electrode case, a salt bridge is provided between the positive electrode or negative electrode in the battery and the mercury / mercury oxide reference electrode outside the battery, and the positive electrode potential with respect to the mercury / mercury oxide reference electrode. The negative electrode potential was measured.

  The measurement results are shown in FIG. FIG. 2 shows discharge curves of the positive electrode and the negative electrode when the batteries (1) and (7) are discharged until the battery voltage reaches 0.2V. In FIG. 2, the solid line shows the discharge curve of the battery (1), and the broken line shows the discharge curve of the battery (7). In these batteries, when comparing the theoretical capacity of the negative electrode with the theoretical capacity of the positive electrode, the negative electrode is excessive, but in fact the negative electrode utilization rate is considerably lower than the positive electrode, so the discharge capacity (discharge time) is mainly Dominated by the negative electrode.

  From FIG. 2, it was found that in the battery (1) using the zinc alloy powder A containing no fine powder having a particle size of 75 μm or less, the negative electrode potential suddenly increased at the end of discharge and the discharge was stopped. On the other hand, in the battery (7) using the zinc alloy powder B containing a large amount of fine powder having a particle size of 75 μm or less, since the zinc alloy has high reactivity, the time during which the negative electrode potential rapidly increases at the end of discharge is extended. As a result, it was found that the positive electrode potential was almost equal to the time when the positive electrode potential dropped rapidly.

  When four batteries are connected in series, there is an inevitable capacity variation in manufacturing, so only one battery with a relatively small capacity among the four batteries is in the overdischarge state from the end of discharge. The remaining three battery voltages may reverse charge and reverse polarity. From the discharge curve of FIG. 2, in the case of the battery (1), it is considered that only one negative electrode is reversed in one battery having a small capacity. On the other hand, in the case of the battery (7), it is considered that both the positive electrode and the negative electrode are reversed in one battery having a small capacity. Comparing the amount of gas generated by the reaction (water decomposition reaction) when the positive electrode and the negative electrode are reversed, when the same amount of electricity is applied to the positive electrode and the negative electrode, the amount of hydrogen gas generated by the reversal of the positive electrode is This is twice the amount of oxygen gas generated by the reversal of the negative electrode. For this reason, in the battery (7) in which the positive electrode is reversed at the time of overdischarge, it is considered that the internal pressure of the battery is significantly increased as compared with the battery (1), and liquid leakage is likely to occur.

Next, FIG. 3 shows discharge curves of the positive electrode and the negative electrode when the batteries (7) and (8) are discharged until the battery voltage becomes 0.2V. In FIG. 3, a solid line shows the discharge curve of the battery (8), and a broken line shows the discharge curve of the battery (7). Even when the zinc alloy powder B containing a large amount of fine powder was used, it was shown that the negative electrode potential at the end of discharge can be properly controlled in the battery (8) using K ₂ S as the additive.

Alkali metal sulfide (K ₂ S) is dissolved in the electrolytic solution and exists as alkali metal ions and sulfide ions in the electrolytic solution. When the generated sulfide ions coexist with zinc, it reacts with zinc to form a relatively inert zinc sulfide coating on the zinc surface. Although the detailed mechanism is not clear, among the zinc alloy powders, the negative electrode potential is rapidly increased before the positive electrode potential rapidly decreases at the end of the discharge due to the effect of the zinc sulfide film formed on the surface of the fine zinc powder. The discharge can be stopped quickly.

In addition, in the battery (9), the positive electrode and negative electrode potential behavior similar to the battery (8) was obtained. When In ₂ S ₃ coexists with zinc in the alkaline electrolyte, it is electrodeposited in the form of metallic indium scattered on the zinc surface, and at the same time, a zinc sulfide film is formed on the remaining zinc surface. Therefore, due to the effect of the formed zinc sulfide film, the negative electrode potential is rapidly increased before the positive electrode potential rapidly decreases at the end of discharge, as in the case of adding alkali metal sulfide (K ₂ S). be able to.

  Table 3 shows the results of quantifying the rising time of the negative electrode potential and the falling time of the positive electrode potential in the measurement of the potential behavior of the positive electrode and the negative electrode. The time for the negative electrode potential to rise is defined as the time from the start of discharge until the negative electrode potential suddenly rises to reach -1.2 V vs. Hg / HgO at the end of discharge. Further, the time for the positive electrode potential to fall is defined as the time from the start of discharge until the positive electrode potential suddenly drops at the end of the discharge to reach −0.6 V vs. Hg / HgO.

When the zinc alloy powder b containing a large amount of fine powder is used, in the batteries (8) and (9) in which K ₂ S or In ₂ S ₃ is added to the negative electrode, the time when the negative electrode potential rises is longer than the time when the positive electrode potential falls. This also shortens the leakage, and can suppress leakage during overdischarge when four batteries are connected in series. This is thought to be due to the fact that the battery reversal with a small capacity in the case of overdischarge in the case where four batteries are connected in series occurs only at the negative electrode, so that the increase in battery internal pressure is suppressed.
From the above, according to the present invention, even when a zinc alloy powder containing a large amount of fine powder is used, leakage during overdischarge can be suppressed while maintaining excellent high-load discharge characteristics.

Example 2
(1) Production of Zinc Alloy Powder In this example, the particle size of zinc alloy powder (the ratio of fine powder having a particle size of 75 μm or less in the zinc alloy powder) was examined.
A zinc alloy powder containing 0.005% by weight of Al, 0.02% by weight of Bi, and 0.03% by weight of In was prepared by a gas atomization method. Then, the obtained alloy powder was sieved into a coarse powder having a particle size range of 35 to 200 mesh and a fine powder having a particle size of 75 μm or less passing through a 200 mesh sieve. Then, the coarse powder and the fine powder are mixed so that the ratio of the fine powder in the alloy powder becomes the value shown in Table 4, and the zinc alloy composition is the same, but the ratio of the fine powder is different. C to G were prepared.

(2) Preparation of gelled negative electrode After adding indium sulfide (0.05% by weight to the zinc alloy powder) to 100 parts by weight of an alkaline aqueous solution containing 36% by weight potassium hydroxide and 2% by weight ZnO, 2 parts by weight of sodium polyacrylate was added and mixed to obtain a gel electrolyte. And this gel electrolyte solution and zinc alloy powder were mixed in the ratio of weight ratio 1: 1.8, and the gel-like negative electrode was obtained.
An alkaline manganese dry battery was produced in the same manner as in Example 1 except that the gelled negative electrode was used.
And at the time of preparation of the gelled negative electrode, alkaline manganese dry batteries C to G were prepared using the zinc alloy powders C to G, respectively, and evaluated in the same manner as described above. The evaluation results are shown in Table 4. The batteries D to F are examples, and the batteries C and G are comparative examples.

  From Table 4, the batteries D to F of the examples of the present invention in which the content of fine powder in the zinc alloy powder is 20 to 50% by weight have good high-load discharge characteristics and at the time of storage after partial discharge. It was found that both the leakage resistance and the leakage resistance during overdischarge were excellent.

In the battery C in which the content of the fine powder in the zinc alloy powder is as low as 15% by weight, the high load discharge characteristics were lowered. In the battery G in which the content of the fine powder in the zinc alloy powder is as high as 55% by weight, the reactivity with the electrolytic solution was too high, and the leakage resistance after partial discharge was greatly reduced. Further, even when the battery G was connected in series and overdischarged, a leaked battery was observed.
In this example, indium sulfide was used as the negative electrode additive. However, similar results can be obtained by using an alkali metal sulfide (such as potassium sulfide) instead.

Example 3
In this example, the amount of potassium sulfide or indium sulfide added to the negative electrode was examined.
To 100 parts by weight of an aqueous solution containing 36% by weight potassium hydroxide and 2% by weight ZnO, the amount of potassium sulfide or indium sulfide shown in Table 5 is added, and then 2 parts by weight of sodium polyacrylate is added and mixed. A gel electrolyte was prepared. In addition, the addition amount (part by weight) of the additive in the negative electrode indicates an amount per 100 parts by weight of the zinc alloy powder used for the negative electrode. And this gel electrolyte solution and the zinc alloy powder B used in Example 1 were mixed in the ratio of weight ratio 1: 1.8, and the gelled negative electrodes (13)-(22) were obtained.
Then, using these gelled negative electrodes (13) to (22), alkaline manganese dry batteries (13) to (22) were produced in the same manner as in Example 1, and evaluated in the same manner as described above. The evaluation results are shown in Table 5. The batteries (14) to (16) and (19) to (21) are examples, and the batteries (13), (17), (18), and (22) are comparative examples.

  Batteries (14) to (16) and batteries (19) of Examples of the present invention in which the amount of potassium sulfide or indium sulfide added to the negative electrode is 0.02 to 0.1 parts by weight per 100 parts by weight of zinc alloy powder In (21), in addition to good high-load discharge characteristics, excellent leakage resistance was obtained both during storage after partial discharge and during overdischarge. In the batteries (13) and (18) in which the amount of potassium sulfide or indium sulfide added in the negative electrode is as small as 0.01 parts by weight per 100 parts by weight of the zinc alloy powder, when multiple batteries are connected in series and overdischarged Leakage was observed.

This is because the amount of the additive in the negative electrode is too small, so that the zinc sulfide film is not sufficiently formed on the surface of the zinc alloy particles, and the negative electrode potential suddenly rises at the end of discharge, causing the positive electrode to switch during overdischarge. This is probably because the effect of deterring the pole was not obtained.
In order to confirm this point, for the batteries (13), (14), (18), and (19), the potentials of the positive electrode and the negative electrode during 10 Ω constant resistance discharge were measured in the same manner as in Example 1. Then, the time for the negative electrode potential to rise and the time for the positive electrode potential to fall were measured. The results are shown in Table 6. In the batteries (13) and (18), the time for the negative electrode potential to rise was longer than the time for the positive electrode potential to fall, and the reversal of the positive electrode was confirmed.

In the batteries (17) and (22) in which the addition amount of potassium sulfide or indium sulfide is as large as 0.12% by weight, the high-load discharge characteristics are deteriorated even when the zinc alloy powder containing a large amount of fine powder is used. This is presumably because the amount of the additive is excessive, and the thickness of the zinc sulfide film formed on the surface of the zinc alloy particles becomes too large to inhibit the discharge reaction.
From the above, it was found that the content of potassium sulfide or indium sulfide in the negative electrode is preferably 0.02 to 0.1 parts by weight per 100 parts by weight of the zinc alloy powder.

Example 4
In this example, the composition of the zinc alloy used for the negative electrode active material was examined.
Zinc alloy powders (23) to (49) containing Bi, In, Al, and Ca in the ratios shown in Table 7 were produced by the gas atomization method. These zinc alloy powders were classified by a sieve so that the particle size range was 35 to 300 mesh and the ratio of fine powder of 75 μm or less passing through a 200 mesh sieve would be 30% by weight.

After adding 0.05% by weight of indium sulfide to 100 parts by weight of an alkaline aqueous solution containing 36% by weight potassium hydroxide and 2% by weight ZnO based on the weight of the zinc alloy powder to be added later, sodium polyacrylate 2 parts by weight was added and mixed to obtain a gel electrolyte. The obtained gel electrolyte solution and zinc alloy powder were mixed at a weight ratio of 1: 1.8 to obtain gelled negative electrodes (23) to (49).
And using these gelled negative electrodes (23) to (49), alkaline manganese dry batteries (23) to (49) were produced and evaluated in the same manner as in Example 1, respectively. The evaluation results are shown in Table 7.

  In the batteries (23) to (49), leakage of overdischarge when four batteries were connected in series could be suppressed by the effect of indium sulfide added to the negative electrode. However, the batteries (23), (28) and (33) in which the total content of bismuth and indium in the zinc alloy powder is less than 0.005% by weight, and the total content of aluminum and calcium are 0.001. In the batteries (38), (42) and (46) which are less than% by weight, the anti-corrosion effect by the additive element in the zinc alloy is insufficient, so that the leakage resistance during storage after partial discharge is lowered.

  Further, the batteries (27), (32) and (37) in which the total content of bismuth and indium in the zinc alloy exceeds 0.1% by weight, and the total content of aluminum and calcium is 0.05% by weight. In the batteries (41), (45), and (49) exceeding 1, the high load discharge characteristics were deteriorated because the amount of these additional elements was excessive and the zinc discharge reaction was inhibited.

  From the above, it was found that the zinc alloy preferably contains 0.005 to 0.1% by weight of bismuth and indium in total and 0.001 to 0.05% by weight of aluminum and calcium in total. In this example, indium sulfide was added to the negative electrode. However, similar results can be obtained by adding an alkali metal sulfide (such as potassium sulfide) instead.

  In Examples 1 to 4, an AA cylindrical alkaline manganese dry battery was manufactured as the zinc alkaline battery of the present invention, but the zinc alkaline battery of the present invention is not limited to this. It can also be suitably used for alkaline manganese dry batteries having a battery size other than AA, or batteries having a button shape or a square shape. Moreover, in the said Examples 1-4, although manganese dioxide was used for the positive electrode active material, the same effect is acquired also when using positive electrode active materials other than manganese dioxide, for example, nickel oxyhydroxide.

  Since the zinc alkaline battery of the present invention is excellent in high load discharge characteristics and liquid leakage resistance, it is suitably used as a power source for general-purpose equipment such as toys and lights and various electronic equipment such as information equipment.

It is the front view which made a part of alkaline dry battery of the example of the present invention a section. It is a figure which shows the discharge curve of the positive electrode and negative electrode at the time of 10 ohm continuous discharge of battery (1) and (7). It is a figure which shows the discharge curve of the positive electrode and negative electrode at the time of 10 ohm continuous discharge of a battery (7) and (8).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Positive electrode case 2 Graphite coating film 3 Positive electrode mixture pellet 4 Separator 5 Bottom paper 6 Gel-like negative electrode 7 Sealing body made of resin 8 Bottom plate 9 Insulating washer 10 Negative electrode current collector 11 Exterior label

Claims (6)

A negative electrode including a zinc alloy powder containing 20 to 50% by weight of a fine powder having a particle size of 75 μm or less, a positive electrode, a separator disposed between the negative electrode and the positive electrode, and an electrolytic solution;
A zinc-alkaline battery characterized in that, in constant resistance discharge, a time for the potential of the negative electrode to rise is shorter than a time for the potential of the positive electrode to fall.   The zinc according to claim 1, wherein the negative electrode contains 0.02 to 0.1 parts by weight of at least one additive selected from the group consisting of alkali metal sulfides and indium sulfides per 100 parts by weight of the zinc alloy powder. Alkaline battery.   The zinc alloy powder contains 0.005 to 0.1% by weight of at least one selected from the group consisting of bismuth and indium, and at least one selected from the group consisting of aluminum and calcium from 0.001 to 0.00. The zinc-alkaline battery according to claim 1, containing 05% by weight. A negative electrode including a zinc alloy powder containing 20 to 50% by weight of a fine powder having a particle size of 75 μm or less, a positive electrode, a separator disposed between the negative electrode and the positive electrode, and an electrolytic solution;
A zinc-alkaline battery characterized by negative electrode capacity regulation in which the potential of the negative electrode rises before the potential of the positive electrode falls at the end of the constant resistance discharge.   5. The zinc according to claim 4, wherein the negative electrode contains 0.02 to 0.1 wt% of at least one additive selected from the group consisting of an alkali metal sulfide and indium sulfide per 100 parts by weight of the zinc alloy powder. Alkaline battery. The zinc alloy powder contains 0.005 to 0.1% by weight of at least one selected from the group consisting of bismuth and indium, and at least one selected from the group consisting of aluminum and calcium from 0.001 to 0.00. The zinc-alkaline battery according to claim 4, containing 05% by weight.

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