JP2006172908A - Alkaline battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an alkaline battery improved greatly in leakage prevention of an electrolyte solution at the time of over-discharge state. <P>SOLUTION: The alkaline battery uses zinc as a principal active material of a negative electrode and manganese dioxide or nickel oxy-hydride as a principal active material of a positive electrode, a potassium hydride water solution as an electrolytic liquid, and a current collection pin in which copper or brass of nearly nail shape is applied with tin plating as a current collector of negative electrode side. The mass concentration of the potassium hydride water solution is 36 to 40 wt.%, and the ratio of zinc and potassium hydride is potassium hydride 37-40 against zinc 100. Furthermore, the thickness of tin plated on the surface of the current collection pin is 0.05 μm-0.5 μm. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an alkaline battery, and more particularly to an alkaline battery in which leakage of an electrolytic solution during an overdischarge state is greatly improved.

  In recent years, electronic devices have become smaller and more portable, and products driven by alkaline batteries have been increasing. A potassium hydroxide aqueous solution is used as the electrolytic solution of the alkaline battery. However, when this electrolytic solution leaks out of the battery, there is a possibility that the electronic device or the human body may be damaged. When an unused battery is stored for a long period of time, zinc is dissolved in an aqueous potassium hydroxide solution, and hydrogen gas is generated on a current collecting pin in contact with the zinc. As a result, the battery internal pressure increases, and the electrolyte solution leaks from the battery sealing portion. As disclosed in the following Patent Document 1, in order to prevent this, a means for preventing the generation of hydrogen gas by plating the surface of the current collecting pin with tin or the like with zinc or the like has come to be used. Yes.

Japanese Patent Application Laid-Open No. 5-135576

  However, in the prior art, an unused battery has an effect on leakage of the electrolyte, but sufficient measures are taken for leakage of the electrolyte when the used battery is left in the equipment. The current situation is that it has not been removed. In particular, a large amount of electrolyte leakage phenomenon is observed in a so-called overdischarge state after zinc has been passivated by a discharge reaction, and countermeasures for this overdischarge leakage liquid are desired.

  In order to solve the above problems, the present invention has been conceived that tin plating of current collecting pins has a great influence on electrolyte leakage of batteries in an overdischarged state, and zinc is used as a main active material of the negative electrode. As the main active material, manganese dioxide or nickel oxyhydroxide was used, an aqueous potassium hydroxide solution was used as the electrolyte, and a current collecting pin in which a substantially nail-like copper or brass was tin-plated was used as a current collector on the negative electrode side. It is an alkaline battery, wherein the mass concentration of the aqueous potassium hydroxide solution is in the range of 36 mass% to 40 mass%, and the ratio of zinc and potassium hydroxide is 100 masses of zinc, and the mass of potassium hydroxide is 37-40. The alkaline battery is characterized in that the thickness of the tin plated on the surface of the current collecting pin is in the range of 0.05 μm to 0.5 μm.

  Tin plating on the current collector pin is effective for leakage of the electrolyte in the undischarged state as described above, but when the plating amount is large, tin dissolves in the electrolyte during overdischarge and cannot be fully discharged. It acts on the remaining zinc and causes hydrogen gas to be generated. Therefore, the thickness of the tin plated on the surface of the current collecting pin is preferably in the range of 0.05 μm to 0.5 μm. If the thickness of the tin plated on the surface of the current collecting pin is limited to be in the range of 0.05 μm to 0.5 μm, the absolute amount of tin itself will be reduced even if the tin elutes during overdischarge. Since there are few, the subject of preventing the leakage of the electrolyte solution at the time of an overdischarge state can be solved more reliably.

  Further, since dissolution of tin occurs when a large amount of potassium hydroxide is present during overdischarge, by limiting the amount of potassium hydroxide added, dissolution of tin does not occur and generation of hydrogen gas can be suppressed. The concentration of the potassium hydroxide aqueous solution is in the range of 36% by mass to 40% by mass, and the ratio of zinc and potassium hydroxide is set to the potassium hydroxide mass of 37 to 40 with respect to the zinc mass of 100. Elution of tin can be suppressed, gas generation can be reduced, and leakage can be prevented.

  In the present invention, a battery satisfying discharge characteristics and overdischarge leakage characteristics can be provided by defining the mass ratio of potassium hydroxide and zinc. Furthermore, the overdischarge leakage characteristics can be further improved by defining the thickness of the tin plating on the surface of the current collecting pin.

  Hereinafter, an embodiment of the present invention will be described with reference to FIG. FIG. 1 shows a configuration example of a cylindrical alkaline battery 1 according to an embodiment of the present invention. This cylindrical alkaline dry battery 1 is arranged in a hollow cylindrical metal positive electrode can 2 having a hollow bottom with an opening, and is arranged so as to be in contact with the hollow cylindrical positive electrode 4 and the positive electrode 4 to form a bottomed cylindrical shape. The formed separator 5, the negative electrode 6 disposed inside the separator 5, and the electrolytic solution are accommodated. The cylindrical battery 1 includes a sealing unit that seals the opening of the positive electrode can 2. The cylindrical battery 1 has a cylindrical outer peripheral surface covered with an exterior label 11. The positive electrode 4 is made of a positive electrode mixture made of manganese dioxide, graphite, an aqueous potassium hydroxide solution that is an electrolytic solution, and the like, and the negative electrode 6 is made of granular zinc and an aqueous potassium hydroxide solution that is an electrolytic solution. It consists of a negative electrode mixture containing a sticky agent and the like in a gel form. This negative electrode mixture is injected into the bottomed cylindrical separator 5. For example, a polyolefin non-woven fabric is used as the material of the separator 5, and the separator 5 is disposed so as to be in contact with the hollow part of the positive electrode 4 formed in a cylindrical shape, and is impregnated with an aqueous potassium hydroxide solution as an electrolytic solution. The sealing unit includes a sealing member 7, a reinforcing member 8, a current collecting pin 9, and a negative electrode terminal 10.

  Further, the sealing member 7 is provided with a through hole at the center thereof, and a nail-shaped current collecting pin 9 is press-fitted from the through hole. The current collecting pin 9 is made of, for example, brass or the like as its material, and its surface is tin-plated, and is press-fitted from the outside into the through hole provided in the central portion of the sealing member 7, It is in contact with the negative electrode.

  In the cylindrical alkaline dry battery, the concentration of the potassium hydroxide aqueous solution as the electrolytic solution is in the range of 36% by mass to 40% by mass, and the ratio of zinc and potassium hydroxide is 37% by mass with respect to 100% by mass of zinc. Furthermore, when the thickness of the tin plated on the surface of the current collecting pin is in the range of 0.05 μm to 0.5 μm, leakage of the electrolytic solution in the overdischarge state can be prevented.

If the concentration of the potassium hydroxide aqueous solution as the electrolyte is less than 36% by mass, the specific gravity becomes too small, OH ⁻ necessary for the negative electrode reaction is insufficient, and a sufficient discharge capacity cannot be obtained, and it exceeds 40% by mass. In particular, the discharge capacity particularly at low temperatures is significantly reduced. The aqueous potassium hydroxide concentration referred to here is the total mass% concentration contained in the positive electrode, negative electrode, and separator of the battery. The lower limit of the mass ratio of zinc and potassium hydroxide is determined by the minimum potassium hydroxide mass required when the battery is discharged with a heavy load of about 1000 mA. The upper limit of the mass ratio of zinc and potassium hydroxide is determined by the maximum potassium hydroxide mass that does not dissolve tin during overdischarge. As the range, the mass ratio of zinc and potassium hydroxide is in the range of potassium hydroxide mass 37 to 40 with respect to zinc mass 100.

  Furthermore, by setting the thickness of the tin plated on the surface of the current collecting pins to be in the range of 0.05 μm to 0.5 μm, it is possible to improve the liquid leakage resistance at the time of non-discharge and overdischarge. If the thickness of the tin plated on the surface of the current collecting pin is less than 0.05 μm, the leakage of the electrolyte during non-discharge increases. On the other hand, if the thickness of the tin plated on the surface of the current collecting pin exceeds 0.5 μm, the amount of tin dissolved during overdischarge increases, and the amount of gas generated from the residual zinc increases, which makes it easy to leak.

  EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example, this invention is not limited to these Examples.

[Example 1]
Cylindrical alkaline batteries having the configuration as shown in FIG. 1 were prepared and their large current discharge characteristics were evaluated. 3.6 g of the positive electrode mixture obtained by uniformly mixing the positive electrode can at a ratio of 85.5% by mass of manganese dioxide, 8% by mass of graphite, and 6.5% by mass of a potassium hydroxide aqueous solution having a mass concentration of 36%. Three pieces formed into a ring shape having an outer diameter of 13.2 mm, an inner diameter of 9.1 mm, and a height of 15 mm were inserted. Next, a bottomed cylindrical separator is inserted into the hollow portion of the positive electrode mixture, and 1.10 g of an aqueous potassium hydroxide solution having a mass concentration of 36%, 65% by mass of zinc, 1% by mass of zinc oxide, and gelation inside the separator. 5.4 g of a negative electrode mixture consisting of 33.5% by mass of an aqueous potassium hydroxide solution having a mass concentration of 0.5% by mass and a mass concentration of 36% was charged. Next, the opening of the positive electrode can is sealed with a sealing unit made up of a negative electrode terminal, a plastic seal, a reinforcing plate, and a current collecting pin with a tin plating of 0.5 μm on the surface of a nail-like brass. It was created. The total mass of potassium hydroxide used in this battery was 1.30 g. Moreover, the mass of zinc was 3.51 g, and the mass ratio of potassium hydroxide to zinc was 37 with respect to 100 masses of zinc hydroxide.

[Example 2]
A cylindrical alkaline battery was produced in the same manner as in Example 1 except that the mass of the 36% potassium hydroxide aqueous solution filled in the separator was 1.20 g. The total mass of potassium hydroxide used in this battery was 1.34 g. The mass of zinc was 3.51 g, and the mass ratio of kalim hydroxide to zinc was 38 mass of potassium hydroxide with respect to 100 masses of zinc.

Example 3
Implementation was performed except that the mass concentration of the potassium hydroxide aqueous solution used for the positive electrode and the negative electrode and the potassium hydroxide aqueous solution filled in the separator was 38%, and the mass of the potassium hydroxide aqueous solution filled in the separator was 1.00 g. A cylindrical alkaline battery was produced by the same production method as in Example 1. The total mass of potassium hydroxide used in this battery was 1.33 g. Further, the mass of zinc was 3.51 g, and the ratio of potassium hydroxide to zinc was 38 mass of potassium hydroxide with respect to 100 masses of zinc.

Example 4
Implementation was performed except that the mass concentration of the potassium hydroxide aqueous solution used for the positive electrode and the negative electrode and the potassium hydroxide aqueous solution filled in the separator was 38%, and the mass of the potassium hydroxide aqueous solution filled in the separator was 1.10 g. A cylindrical alkaline battery was produced by the same production method as in Example 1. The total mass of potassium hydroxide used in this battery was 1.37 g. Moreover, the mass of zinc was 3.51 g, and the ratio of potassium hydroxide to zinc was 39 potassium hydroxide mass per 100 mass zinc.

Example 5
Implementation was performed except that the mass concentration of the potassium hydroxide aqueous solution used for the positive electrode and the negative electrode and the potassium hydroxide aqueous solution filled in the separator was 40%, and the mass of the potassium hydroxide aqueous solution filled in the separator was 1.00 g. A cylindrical alkaline battery was produced by the same production method as in Example 1. The total mass of potassium hydroxide used in this battery was 1.40 g. The mass of zinc was 3.51 g, and the ratio of potassium hydroxide to zinc was 40 mass of potassium hydroxide with respect to 100 mass of zinc.

[Comparative Example 1]
A cylindrical alkaline battery was produced by the same production method as in Example 1 except that the mass of the 36% by weight potassium hydroxide aqueous solution filled in the separator was 1.00 g. The total mass of potassium hydroxide used in this battery was 1.26 g. Moreover, the mass of zinc was 3.51 g, and the ratio of potassium hydroxide and zinc was 36 mass of potassium hydroxide with respect to 100 masses of zinc.

[Comparative Example 2]
A cylindrical alkaline battery was produced by the same production method as in Example 3 except that the mass of the 38% potassium hydroxide aqueous solution filled in the separator was 1.25 g. The total mass of potassium hydroxide used in this battery was 1.43 g. Further, the mass of zinc was 3.51 g, and the ratio of potassium hydroxide to zinc was 41 mass of potassium hydroxide with respect to 100 masses of zinc.

[Comparative Example 3]
A cylindrical alkaline battery was produced in the same manner as in Example 5 except that the mass of the 40% potassium hydroxide aqueous solution filled in the separator was 1.10 g. The total mass of potassium hydroxide used in this battery was 1.44 g. Further, the mass of zinc was 3.51 g, and the ratio of potassium hydroxide to zinc was 41 mass of potassium hydroxide with respect to 100 masses of zinc.

[Evaluation methods of Examples 1 to 5 and Comparative Examples 1 to 3]
30 batteries of Examples 1 to 5 and Comparative Examples 1 to 3 obtained as described above were prepared. Each battery was discharged 10 times at a constant current of 1000 mA, and a test was conducted to measure the discharge time up to 0.9V. The results are shown in Table 1. The numerical values in the table are all average values of 10 batteries (n = 10).

(Undischarged liquid leakage test)
Ten batteries were stored in an undischarged state in a high-temperature bath at 60 ° C. and 90% humidity for 60 days, and the rate of leakage was measured. The results are shown in Table 1.

(Overdischarge leakage test)
Each battery was discharged at 10Ω for 48 hours, and then stored in a high-temperature bath at 60 ° C. for 40 days, and the occurrence rate of liquid leakage was measured. The results are shown in Table 1.

  As shown in Table 1, batteries other than Comparative Example 1 have a discharge time of 50 minutes or more. In the battery of Comparative Example 1, the mass ratio of potassium hydroxide to zinc was as low as 36, and a sufficient discharge capacity was not obtained. The batteries of Comparative Examples 2 and 3 leaked 100% in the overdischarge leakage test, whereas the batteries of Examples 1 to 5 and Comparative Example 1 had a good leak rate of 50% or less. Is shown. In particular, in Example 1, the leakage occurrence rate was 0 for both undischarged leakage and overdischarge leakage.

  Next, in order to examine the influence of the amount of tin plating on the surface of the current collecting pin on the liquid leakage test, batteries of Examples 6 to 7 and Comparative Examples 4 to 5 were made as prototypes.

Example 6
A cylindrical alkaline battery was produced by the same production method as in Example 1 except that a current collecting pin having a surface of brass plated with 0.05 μm of tin was used.

Example 7
A cylindrical alkaline battery was produced by the same production method as in Example 1 except that a current collecting pin having a 0.1 μm tin plating on the surface of brass was used.

[Comparative Example 4]
A cylindrical alkaline battery was produced by the same production method as in Example 1 except that a current collecting pin not plated with tin was used on the surface of brass.

[Comparative Example 5]
A cylindrical alkaline battery was produced by the same production method as in Example 1 except that the thickness of the tin plating was 0.03 μm on the brass surface.

[Evaluation methods of Examples 6 to 7 and Comparative Examples 4 to 5]
30 batteries of Examples 6 to 7 and Comparative Examples 4 to 5 obtained as described above were prepared. Each battery was discharged 10 times at a constant current of 1000 mA, and a test was conducted to measure the discharge time up to 0.9V. The results are shown in Table 2. The numerical values in the table are all average values of 10 batteries (n = 10).

(Undischarged liquid leakage test)
Ten batteries were stored in an undischarged state in a high-temperature bath at 60 ° C. and 90% humidity for 60 days, and the rate of leakage was measured. The results are shown in Table 2.

(Overdischarge leakage test)
Each battery was discharged at 10Ω for 48 hours, and then stored in a high-temperature bath at 60 ° C. for 40 days, and the occurrence rate of liquid leakage was measured. The results are shown in Table 2.

  From the results in Table 2, the undischarged liquid leakage of batteries other than Comparative Example 4 and Comparative Example 5 was zero. Examples with zero undischarged leakage and overdischarge leakage were Example 6 and Example 7.

  From the results of Tables 1 and 2, the concentration of the potassium hydroxide aqueous solution is in the range of 36% by mass to 40% by mass, and the ratio of zinc to potassium hydroxide is 100% of the mass of zinc. Thus, it can be proved that the amount of gas generation can be reduced and leakage can be prevented. Furthermore, by setting the thickness of the tin plated on the surface of the current collecting pins to be in the range of 0.05 μm to 0.5 μm, it is possible to further enhance the effect of preventing leakage at the time of non-discharge and overdischarge.

It is a figure which shows the example of 1 structure of the cylindrical battery concerning this invention.

Explanation of symbols

1 Cylindrical battery,
2 Positive electrode can 3 Conductive paint 4 Positive electrode 5 Separator 6 Negative electrode 7 Sealing member 8 Reinforcing member 9 Current collecting pin 10 Negative electrode terminal 11 Exterior label

Claims (2)

  Zinc is used as the main active material of the negative electrode, manganese dioxide or nickel oxyhydroxide is used as the main active material of the positive electrode, an aqueous potassium hydroxide solution is used as the electrolyte, and substantially nail-shaped copper or brass is used as the current collector on the negative electrode side. An alkaline battery using a tin-plated current collecting pin, wherein the mass concentration of the potassium hydroxide aqueous solution is in the range of 36 mass% to 40 mass%, and the ratio of zinc to potassium hydroxide is 100 mass of zinc. On the other hand, an alkaline battery characterized in that the mass of potassium hydroxide is in the range of 37-40. 2. The alkaline battery according to claim 1, wherein a thickness of tin plated on the surface of the current collecting pin is in a range of 0.05 [mu] m to 0.5 [mu] m.

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