JP2007173254A - Alkaline cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an alkaline cell excellent in load characteristics, prevented from lowering of gas-generation when reacting with electrolyte and preservation property, restrained from heat generation at abnormality. <P>SOLUTION: The alkaline cell is formed by enclosing a cathode mixture containing alkaline electrolyte (A) prepared by dissolving either manganese dioxide or nickel oxide, conductive agent, and potassium hydroxide, separator, and an anode mixture prepared by dissolving zinc alloy powder, gelatinizer, and potassium hydroxide, in an envelope. The density of the potassium hydroxide in the alkaline electrolyte (A) of the cathode mixture is not less than 45 wt.%, and the density of the potassium hydroxide in the alkaline electrolyte (B) of the anode mixture is not more than 35 wt.%. Zinc alloy powder having content of the powder passing through a sieve of 200 mesh by 4 to 40% is used as the zinc alloy powder for the anode. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an alkaline battery. More specifically, the present invention relates to an alkaline battery that has excellent load characteristics while suppressing heat generation behavior when an abnormality occurs.

  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. In particular, in digital cameras that have been widely used in recent years, in order to maximize the number of images that can be taken, it is necessary to increase the battery capacity and further improve the load characteristics such as the large current discharge characteristics. Possible battery designs are being studied.

  In order to increase the capacity of the battery, it is necessary to increase the filling amount of the active material. However, if the active material is not effectively used for discharging, the capacity cannot be increased. Therefore, simply increasing the filling amount of the active material. You can't achieve your goal by just doing it. Since the discharge capacity is determined in view of the utilization factor of the active material, it is important to ensure good conductivity between the active materials and to perform uniform filling.

  Moreover, to improve the load characteristics, it is necessary to increase the reaction area of the active material and improve the conductivity, but as the reaction area of the active material increases, gas generation due to reaction with the electrolyte tends to occur. Therefore, in the negative electrode, it is common to alloy zinc, which is a negative electrode active material, with an additive element that can suppress gas generation.

  However, since the conductivity tends to decrease due to an increase in the content of the additive element, it is difficult to achieve both suppression of gas generation and load characteristics. Moreover, in order to suppress self-discharge, the electrolyte solution generally contains a zinc compound, particularly zinc oxide, but this also deteriorates the load characteristics.

  Even if a battery having excellent load characteristics can be designed, another problem shown below arises. Therefore, there remains a problem to be solved for a practical battery. In other words, when the battery is stored at a high temperature, the battery becomes hot due to heat generated in the battery when an excessive current flows through the battery due to malfunction of the electronic device or accidental short circuit of the battery. Thus, there arises a problem that dangers such as leakage of the electrolyte and rupture of the battery occur. In particular, the higher the capacity of the battery and the higher the load, the higher the reactivity and the greater the amount of heat generated. Therefore, the solution of the above problem becomes more important.

  Therefore, it is required to design an alkaline battery that has high capacity and excellent load characteristics, but also has excellent storability and is unlikely to cause abnormal behavior such as rapid temperature rise due to heat generation when an abnormality such as a short circuit occurs. .

  The present invention has been made in view of the above circumstances, and is an alkaline battery that has excellent load characteristics, prevents gas generation due to reaction with an electrolytic solution and deterioration of storage stability, and suppresses heat generation behavior when an abnormality occurs. The issue is to provide.

  The alkaline battery of the present invention includes a positive electrode mixture, a separator, and a zinc alloy powder and a gelling agent containing at least one of manganese dioxide and nickel oxide, a conductive agent, and an alkaline electrolyte (A) in which potassium hydroxide is dissolved. And an alkaline electrolyte (B) in which potassium hydroxide is dissolved, enclosed in an exterior body, an alkaline battery, wherein the positive electrode mixture alkaline electrolyte (A) The potassium hydroxide concentration is 45% by mass or more, the potassium hydroxide concentration of the alkaline electrolyte (B) of the negative electrode mixture is 35% by mass or less, and passes through a 200 mesh sieve as the zinc alloy powder of the negative electrode. A zinc alloy powder having a ratio of 4 to 40% by mass to be used is used.

  ADVANTAGE OF THE INVENTION According to this invention, while being excellent in load characteristics and preventing the gas generation | occurrence | production and storage property fall by reaction with electrolyte solution, the alkaline battery which suppressed the heat-generation behavior at the time of abnormality generation can be provided.

  The present invention is characterized in that an alkaline electrolyte (A) containing potassium hydroxide at a high concentration of 45% by mass or more is used in the formation of the positive electrode mixture. The positive electrode mixture is formed by mixing at least one of manganese dioxide and nickel oxide, a conductive agent, and the alkaline electrolyte (A). The alkaline electrolyte (A) has a potassium hydroxide concentration of 45 mass. When the content is at least%, a homogeneous mixture is formed, and the mixture can be filled at a high density and the conductivity of the entire mixture can be improved. Therefore, it is possible to realize a high capacity design of the battery and to improve load characteristics.

  On the other hand, when the battery is short-circuited due to the increased reactivity of the positive electrode, an excessive short-circuit current flows immediately after the occurrence of the short-circuit, but due to the rapid discharge reaction of the zinc alloy powder of the negative electrode that occurs at this time, An oxide layer that suppresses the reaction is formed on the surface of the zinc alloy powder at once, and the short-circuit current decreases in a short time. For this reason, it is considered that the heat generated by the discharge is relatively small, the battery temperature rise is suppressed, and abnormal behavior such as leakage of the electrolytic solution or battery rupture can be prevented. Here, if the alkaline electrolyte containing potassium hydroxide at a concentration exceeding 50% by mass is used as the electrolytic solution, the above effect can be more easily obtained, and the alkaline electrolyte (B) of the negative electrode mixture described later Since a lower potassium hydroxide concentration can be used, particularly desirable results can be obtained in the present invention.

  However, since the saturated concentration of potassium hydroxide at room temperature is approximately 50% by mass, it is desirable to control the temperature of the mixture when using an alkaline electrolyte having a higher concentration. That is, since the preparation of the alkaline electrolyte is usually performed under conditions that are heated so that potassium hydroxide is easily dissolved, it is easy to produce a potassium hydroxide aqueous solution having a concentration exceeding 50% by mass. However, when the mixture is produced at or near room temperature, it is highly possible that potassium hydroxide exceeding the saturation amount at that temperature precipitates and the formation of a homogeneous mixture is impaired. Therefore, it is desirable to mix the mixture composition in a heated atmosphere so that the electrolytic solution does not reach a saturated concentration to produce a positive electrode mixture. As the temperature condition, it is desirable to carry out at 35 ° C. or higher in order to increase the saturated dissolution amount of potassium hydroxide. . In addition, even when the potassium hydroxide concentration is 45 to 50% by mass, the dispersibility of the composition is improved and a homogeneous mixture is easily formed by mixing the mixture composition in a heated atmosphere. .

  Moreover, as said electrically conductive agent, carbon materials, such as graphite, acetylene black, carbon black, and fibrous carbon, can be mainly used, However, Among these, graphite is used preferably. In the present invention, as the active material of the positive electrode, manganese dioxide, nickel oxyhydroxide, nickel oxide represented by a compound in which part of nickel is substituted with another element, or any of them is used. Although mixed and used, it is desirable to mix graphite at a ratio of 6 parts by mass or more with respect to 100 parts by mass of the total amount of manganese dioxide and nickel oxide as positive electrode active materials. This is because the effect of suppressing the abnormal heat generation at the time of the short circuit is more easily exhibited. On the other hand, since the reduction of the active material filling amount is not preferable, the proportion of graphite is desirably 8.5 parts by mass or less with respect to 100 parts by mass of the total amount of manganese dioxide and nickel oxide as the positive electrode active material.

  As a constituent element other than the above, a small amount of a binder such as carboxymethyl cellulose, methyl cellulose, polyacrylate, polytetrafluoroethylene, and polyethylene can be contained in the positive electrode mixture. If the added amount is large, adverse effects such as a decrease in conductivity occur, but if the added amount is small, the contact between the conductive agent and the active material is improved, which is advantageous.

  The second feature of the present invention is that an alkaline electrolyte (B) containing potassium hydroxide at a concentration of 35% by mass or less is used in the formation of the negative electrode mixture. The negative electrode mixture is formed by mixing a zinc alloy powder, a gelling agent, and an alkaline electrolyte (B) in which potassium hydroxide is dissolved to form a gel-like mixture. By adjusting the potassium concentration to 35% by mass or less, the state of the oxide coating on the surface of the zinc alloy powder can be made appropriate, the conductivity of the alkaline electrolyte is increased, the load characteristics are improved, and the short circuit is also achieved. Since the discharge reaction proceeds easily at the initial stage of the time, it seems that the above-described effect of suppressing abnormal heat generation is likely to be obtained.

  Furthermore, in the formation of the negative electrode mixture, the present invention uses a zinc alloy powder in which the proportion of the powder passing through the 200 mesh sieve is 4% by mass or more and 40% by mass or less as the zinc alloy powder. Features. In the zinc alloy powder, if the ratio of the powder passing through the 200 mesh sieve is 4% by mass or more, the characteristics in high-current pulse discharge are improved. The proportion of the powder passing through the 200 mesh sieve in the zinc alloy powder is more preferably 15% by mass or more, while it is 40% by mass or less in order to form a negative electrode mixture having a uniform and good fluidity. Is desirable.

  Moreover, it is desirable to contain indium, bismuth and aluminum as alloy elements of the zinc alloy powder. The surface condition of the zinc alloy powder can be made more suitable, not only affecting the load characteristics and the effect of suppressing abnormal heat generation, but also increasing the proportion of fine particles to increase the reaction area of the zinc alloy powder. This is because the reaction with the electrolytic solution can be suppressed and gas generation can be prevented. As contents of these elements, indium, bismuth and aluminum are preferably 0.03 to 0.07% by mass, 0.007 to 0.025% by mass and 0.001 to 0.004% by mass, respectively. .

  Moreover, the surface state of a zinc alloy powder can be made more suitable also by making an alkaline electrolyte (B) contain a zinc compound. As the zinc compound, zinc oxide, zinc silicate, zinc titanate, zinc molybdate and the like can be used, and zinc oxide is preferably used. In order to increase the solubility of the zinc compound, the potassium hydroxide concentration of the alkaline electrolyte (B) is desirably 20% by mass or more. In addition, a zinc compound can also be contained in the alkaline electrolyte (A) of the positive electrode mixture or the alkaline electrolyte (C) described later.

  As constituent elements other than the above, the negative electrode mixture may contain a small amount of an indium compound such as indium oxide or a bismuth compound such as bismuth oxide. When these compounds are contained, gas generation due to the reaction between the zinc alloy powder and the electrolytic solution can be prevented more effectively, but the load characteristics may be reduced, so the content is determined as necessary. Is done.

  The alkaline battery of the present invention is produced by enclosing the positive electrode mixture and the negative electrode mixture together with a separator in the exterior body. However, there are many cases where the amount of liquid is insufficient with only the alkaline electrolyte contained in the positive electrode mixture and the negative electrode mixture. In this case, a step of further injecting the electrolyte and causing the separator to absorb it is necessary. The alkaline electrolyte (C) injected at this time is preferably one in which potassium hydroxide is dissolved at a concentration of 20 to 40% by mass. That is, the effect of suppressing the abnormal heat generation at the time of short circuit described above also depends on the potassium hydroxide concentration of the alkaline electrolyte (C), and it is desirable to use an electrolyte having a concentration as low as possible, less than 35% by mass. If so, more favorable results can be obtained. On the other hand, after the assembly, the alkaline electrolytes (A) to (C) in the battery system are diffused and mixed, and gradually approach a uniform electrolytic solution. It is desirable to adjust the potassium hydroxide concentration of each of the alkaline electrolytes (A) to (C) so that the average concentration of is within a suitable range. It is desirable to contain potassium hydroxide at a concentration.

  Further, if the zinc compound is contained not only in the alkaline electrolyte (B) but also in (A) and (C), the effect of reducing characteristic deterioration when the battery is stored at a high temperature is increased. If the potassium hydroxide concentration of the alkaline electrolyte (C) is set to 20% by mass or more, the solubility of the zinc compound increases, which is advantageous from the viewpoint of adding the zinc compound.

  It is desirable to design the battery so that the average concentration of potassium hydroxide in the entire alkaline electrolyte is 30 to 37% by mass. When the potassium hydroxide concentration is 30% by mass or more, the storage property when stored at a high temperature is improved, and if it is 33.5% by mass or more, more excellent characteristics are obtained. On the other hand, when the content is 37% by mass or less, load characteristics are improved, and an effect of suppressing abnormal heat generation during a short circuit is easily obtained.

  In the present invention, the shape of the battery is not particularly limited. However, when a cylindrical metal outer can is used as the outer casing, the positive electrode mixture formed in a ring shape is disposed inside the outer can, and inside the outer casing can. A cup-shaped separator is placed, and then the alkaline electrolyte (C) is injected and absorbed by the separator. Further, the negative electrode mixture is filled in the gap inside the separator, and these components are sealed inside the outer can. As a result, the battery is assembled. As shown in FIG. 2, in the cylindrical alkaline battery, when the opening end 1 a of the outer can 1 is folded inward and sealed, the negative electrode terminal plate 207 is prevented from being deformed, and the sealing body 6 In general, a metal washer 9 (a disk-shaped metal plate) is used as an instruction means for supporting the seal from the inside, but there is a problem that the volume occupied by the sealing portion 10 is increased.

  On the other hand, in the battery of FIG. 1 in which the metal washer is eliminated and the negative electrode terminal plate 7 is used as an instruction means for supporting the sealing body 6 from the inside, the volume occupied by the sealing portion 10 can be reduced. On the other hand, the filling amount of the mixture can be further increased. However, as the capacity of the battery is increased, the heat generation at the time of short circuit is further increased. However, even in a battery with such a high capacity design, by using the present invention, the abnormal heat generation behavior of the battery can be prevented, so that the practicality of the battery can be enhanced.

  Examples of the present invention will be described below. Of course, the present invention is not limited to these examples.

(Reference Example 1)
Electrolytic manganese dioxide, graphite, polytetrafluoroethylene powder and alkaline electrolyte (A) (56% by mass aqueous potassium hydroxide solution containing 2.9% by mass of zinc oxide) 87.6: 6.7: 0.2: The mixture was mixed at a mass ratio of 5.5 to prepare a positive electrode mixture. The positive electrode mixture was produced at a temperature of 50 ° C. Moreover, the ratio of the graphite with respect to 100 mass parts of manganese dioxides in the said positive electrode mixture was 7.6 mass parts.

Also, zinc alloy powder, polyacrylic acid soda, polyacrylic acid, and alkaline electrolyte (B) containing 0.05% by mass, 0.05% by mass, and 0.005% by mass of indium, bismuth, and aluminum, respectively. (A 32% by mass aqueous potassium hydroxide solution containing 2.2% by mass of zinc oxide) was mixed at a mass ratio of 39: 0.2: 0.2: 18 to prepare a gelled negative electrode mixture. The zinc alloy powder is a zinc alloy powder having an average particle size of 122 μm, passing through all 80 mesh screens and not passing through 200 mesh screens, and has an apparent density of 2.65 g / cm. ³ .

  As the exterior body, the sealing portion 10 has a thickness of 0.25 mm, the body portion 20 has a thickness of 0.16 mm, and in order to prevent the positive terminal 1b from being dented when the battery is dropped, Using an outer can 1 for AA alkaline dry batteries made of a killed steel plate having a can thickness slightly thicker than that of the barrel portion 20, an alkaline battery was produced as follows.

  11 g of the positive electrode mixture was press-molded into a cylindrical shape having an inner diameter of 9.1 mm, an outer diameter of 13.7 mm, and a height of 41.7 mm to form a positive electrode, which was inserted into the outer can 1. Thereafter, a groove is applied 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 surface of the outer can 1 is reached to the groove position. 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. The separator 3 was loaded inside the positive electrode 1 inserted in the outer can, and further, alkaline electrolyte (C) (32% by mass potassium hydroxide aqueous solution containing 2.2% by mass of zinc oxide) 1.35 g Was poured into the outer can and soaked into the separator 3. Next, 5.74 g of the negative electrode mixture was filled into the separator 3 to form the negative electrode 4, and further combined with the sealing body 6 made of nylon 6-6 and formed by punching / pressing with a thickness of 0. A negative electrode current collector rod 5 (made of brass whose surface is tin-plated) attached to a 4 mm negative electrode terminal plate 7 (made of nickel-plated steel plate) by welding is inserted into the negative electrode central portion, and from the outside of the open end 1a of the outer can 1 The AA alkaline battery shown in FIG. 1 was produced by caulking by a spinning method. An insulating plate 8 was mounted between the open end of the outer can 1 and the negative terminal plate 7 to prevent a short circuit.

  In the above battery, the alkaline electrolyte in the assembled battery system contained 35% by mass of potassium hydroxide on average.

(Reference Example 2)
Reference was made except that electrolytic manganese dioxide, graphite, polytetrafluoroethylene powder and alkaline electrolyte (A) were mixed at a mass ratio of 89.3: 5.1: 0.2: 5.6 to prepare a positive electrode mixture. In the same manner as in Example 1, an AA alkaline battery was produced. In this positive electrode mixture, the ratio of graphite to 100 parts by mass of manganese dioxide was 5.7 parts by mass.

(Reference Example 3)
AA alkaline batteries were produced in the same manner as in Reference Example 1 except that 30% by mass potassium hydroxide aqueous solution containing 2.0% by mass of zinc oxide was used as the alkaline electrolytes (B) and (C). . The alkaline electrolyte in the assembled battery system contained 33% by mass of potassium hydroxide on average.

Example 1
Indium, bismuth and aluminum are contained in the proportions of 0.05% by mass, 0.015% by mass and 0.003% by mass, respectively, as the zinc alloy powder of the negative electrode, the average particle size is 200 μm, and all 35 mesh sieves Similar to Reference Example 1, except that a zinc alloy powder that passes through and passes through a 200-mesh sieve is 6% by mass and the apparent density is 2.9 g / cm ^3. A three-type alkaline battery was produced.

(Example 2)
The proportion of the negative electrode zinc alloy powder having an average particle diameter of 135 μm, passing through all 35 mesh sieves and passing through 200 mesh sieves is 20% by mass, and the apparent density is 2.9 g / AA alkaline batteries were produced in the same manner as in Reference Example 1 except that the zinc alloy powder of cm ³ was used.

  For each of the 12 batteries according to the example and the reference example manufactured as described above, a pulse discharge test was performed in which a base discharge current was 0.5 A and a pulse current of 2 A was supplied for 2 seconds at 30 second intervals. The number of pulse discharges required until the voltage at the time when the pulse current flowed decreased to 1.0 V or less was measured to obtain an average value, and the load characteristics were evaluated.

  In addition, for each of 12 batteries different from the above, a thermocouple is fixed with an aluminum tape at the center of the side surface of the battery outer can, and the surface temperature of the outer can when the battery is short-circuited is measured. The average value was obtained and the heat generation behavior when an abnormality occurred was evaluated. At this time, the time change of the current value was also measured for the battery of Reference Example 3. The change from the short-circuit start of the short-circuit current of the battery of Reference Example 3 and the outer can surface is shown in FIG.

  Furthermore, for each of 24 batteries, first, 12 batteries were discharged with a discharge current of 1 A, and the discharge time until 0.9 V or less was measured. The average time was taken as the discharge time before storage. In addition, the remaining 12 pieces were stored in a constant temperature bath at 60 ° C. for 20 days, taken out, cooled at room temperature for 1 day, and then discharged at a discharge current of 1 A and measured for a discharge time of 0.9 V or less. The average time was taken as the discharge time after storage, the ratio of the discharge time after storage to the discharge time before storage was determined as the capacity retention, and the storability of the battery at high temperature was evaluated. Table 1 summarizes the measurement results of the number of pulse discharges, the outer can surface temperature, and the capacity retention. Gas generation was not a problem.

  As is clear from the results in Table 1, the batteries of the examples of the present invention were excellent in load characteristics, suppressed the heat generation behavior when an abnormality occurred, and were excellent in storage at high temperatures.

It is sectional drawing which shows the whole structure of the alkaline battery using a negative electrode terminal board as an instruction | indication means which supports a sealing body from the inside. It is sectional drawing which shows the general structure of the conventional alkaline battery. It is a graph which shows the change of a short circuit current and the armored can surface temperature when the alkaline battery of the reference example 3 is short-circuited.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Outer can 1a Open end 2 of outer can 2 Positive electrode 3 Separator 4 Negative electrode 5 Negative electrode collector rod 6 Sealing body 7,207 Negative electrode terminal board 8 Insulating plate 9 Metal washer 10 Sealing part 20 Trunk part

Claims (9)

A positive electrode mixture containing at least one of manganese dioxide and nickel oxide, a conductive agent and an alkaline electrolyte (A) in which potassium hydroxide is dissolved, a separator, and a zinc alloy powder, a gelling agent and potassium hydroxide are dissolved. An alkaline battery produced by enclosing a negative electrode mixture containing an alkaline electrolyte (B) inside an exterior body,
The potassium hydroxide concentration of the alkaline electrolyte (A) of the positive electrode mixture is 45% by mass or more, and the potassium hydroxide concentration of the alkaline electrolyte (B) of the negative electrode mixture is 35% by mass or less,
An alkaline battery using a zinc alloy powder having a ratio of powder passing through a 200 mesh sieve as 4 to 40% by mass as a zinc alloy powder for a negative electrode.   The alkaline battery according to claim 1, wherein the potassium hydroxide concentration of the alkaline electrolyte (A) of the positive electrode mixture exceeds 50 mass%.   The alkaline battery according to claim 1, wherein the concentration of potassium hydroxide in the alkaline electrolyte (B) of the negative electrode mixture is 20% by mass or more.   The alkaline electrolyte (C) in which potassium hydroxide is dissolved at a concentration of 20 to 40% by mass is injected into the exterior body and absorbed by the separator when the battery is assembled. The alkaline battery according to any one of the above.   The alkaline battery according to claim 4, wherein at least one of the alkaline electrolytes (A) to (C) contains a zinc compound.   After the assembly of the battery, the potassium hydroxide concentration of each of the alkaline electrolytes (A) to (C) was adjusted so that the average potassium hydroxide concentration of the alkaline electrolyte in the battery system was 30 to 37% by mass. The alkaline battery according to claim 4 or 5, wherein   The alkaline battery according to claim 1, wherein the zinc alloy powder of the negative electrode contains indium, bismuth and aluminum.   The contents of indium, bismuth and aluminum contained in the zinc alloy powder are 0.03 to 0.07 mass%, 0.007 to 0.025 mass% and 0.001 to 0.004 mass%, respectively. The alkaline battery according to claim 7. The alkaline battery according to any one of claims 1 to 8, wherein graphite is used as a conductive agent of the positive electrode, and graphite is 6 to 8.5 parts by mass with respect to 100 parts by mass of manganese dioxide and nickel oxide. .

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