JP2008135237A - Flat zinc battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a flat zinc battery excellent in an anti-leak property during high-temperature storage. <P>SOLUTION: The flat zinc battery is provided with a negative electrode case 10 having as an inner face a surface layer made of at least a kind selected from a group consisting of Cu, In, Sn, Bi, and Zn, a gelatinous negative electrode 9 in contact with the surface layer of the negative electrode case 10 and containing a non-mercury zinc alloy and alkaline solution, a positive electrode case 1 fixed in caulking to the negative electrode case 10, and an insulation gasket 13 having a circular outer wall 14a and a folded part 14b with one of the open end of the outer wall 14a folded inward, with the former 14a arranged between an outer face of the negative electrode case 10 and an inner face of the positive electrode case 1, and with the latter 14b coating an inner peripheral edge part of the negative electrode case 10. The insulation gasket has a protrusion 14c fitted at a bottom face of the folded part 14b. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a flat zinc battery.

  An air zinc battery is known as an example of a flat zinc battery. Hearing aids can be cited as the main use of zinc-air batteries. In Japan, the demand for hearing aids is increasing as the population ages. Furthermore, the shape of the hearing aid is also shifting from the ear-hook type to the ear hole type, and a battery with higher safety is required. Liquid leakage resistance is an item related to battery safety. It has been found that this leakage resistance characteristic depends on the sealing properties of the battery. As a battery sealing method, an insulating gasket made of synthetic resin such as nylon is placed between the positive electrode case and the negative electrode case, and the insulating gasket and the positive electrode case, and the insulating gasket and the negative electrode case are adhered by caulking. Most of them are.

  The leakage of the electrolytic solution is more likely to occur from the contact surface between the negative electrode case and the gasket than from the contact surface between the positive electrode case and the insulating gasket. For this reason, as shown in Patent Documents 1 to 4, the gap between the negative electrode case and the insulating gasket is filled with a sealant.

In recent years, there has been an increasing demand for dehydration in air zinc batteries due to environmental problems, using a non-zinc-free zinc alloy as a negative electrode active material and arranging a metal with high hydrogen overvoltage such as Sn and In on the inner surface of the negative electrode case. Things have been done. However, when such a negative electrode active material and a negative electrode case are used, sufficient leakage resistance characteristics cannot be obtained at the time of high-temperature storage with only the sealant described in Patent Documents 1 to 4.
Japanese Patent Publication No.62-52426 Japanese Patent Publication No.62-31783 Japanese Patent Laid-Open No. 8-7918 JP-A-9-129204

  An object of the present invention is to provide a flat zinc battery having excellent leakage resistance during high temperature storage.

A flat zinc battery according to the present invention comprises a negative electrode case having an inner surface of at least one surface selected from the group consisting of Cu, In, Sn, Bi and Zn,
In contact with the surface of the negative electrode case, a gelled negative electrode containing a zinc-free zinc alloy and an alkaline electrolyte;
A positive electrode case fixed by caulking to the negative electrode case;
An annular outer wall; and a folded portion in which one open end of the outer wall is folded inward, the outer wall being disposed between the outer surface of the negative electrode case and the inner surface of the positive electrode case, and the folded portion is A flat zinc battery comprising an insulating gasket covering the inner peripheral edge of the negative electrode case,
The insulating gasket has a protrusion on the bottom surface of the folded portion.

  ADVANTAGE OF THE INVENTION According to this invention, the flat type zinc battery which is excellent in the leak-proof characteristic at the time of high temperature storage can be provided.

  The surface layer made of at least one selected from the group consisting of Cu, In, Sn, Bi and Zn constituting the inner surface of the negative electrode case suppresses the formation of a local battery by the zinc-free zinc alloy and the negative electrode case. On the other hand, it has the property of dissolving in an alkaline electrolyte contained in the gelled negative electrode. For this reason, if the adhesion between the negative electrode case and the insulating gasket is not sufficient, when the surface layer elutes into the alkaline electrolyte due to high temperature storage or the like, the alkaline electrolyte leaks out from between the negative electrode case and the insulating gasket. It reaches the liquid.

  According to the present invention, in the flat zinc battery using the negative electrode case and the negative electrode active substance, when a protrusion is provided on the bottom surface of the folded portion of the insulating gasket, the folded portion is pushed up by the stress applied to the insulating gasket during caulking and fixing. It has been found that it adheres strongly to the surface layer of the negative electrode case, and the amount of leakage during overdischarge and storage at high temperature is reduced.

  Hereinafter, embodiments of a flat zinc battery according to the present invention will be described with reference to the drawings.

(First embodiment)
1 is a cross-sectional view showing a zinc-air battery according to the first embodiment of the present invention, FIG. 2 is an enlarged cross-sectional view showing a main part of the zinc-air battery of FIG. 1, and FIG. Sectional drawing obtained when the insulating gasket used is cut | disconnected along radial direction is shown.

  As shown in FIG. 1, a positive electrode case 1 having a bottomed cylindrical shape has an upper end 2 of an opening thereof bent inward by caulking. The positive electrode case 1 has an air hole 3 at the bottom. The air hole 3 of the positive electrode case 1 is temporarily blocked with a seal tape 16 attached to the bottom surface of the positive electrode case 1 in order to prevent useless discharge when not in use. The positive electrode case 1 is made of a metal such as stainless steel and serves also as a positive electrode terminal. A positive electrode catalyst layer 4 is accommodated in the positive electrode case 1. As the positive electrode catalyst contained in the positive electrode catalyst layer 4, for example, a mixture of activated carbon and manganese oxide (for example, manganese dioxide) can be used. The positive electrode catalyst layer 4 is obtained, for example, by mixing activated carbon, manganese oxide, expanded graphite as a conductive material, and polytetrafluoroethylene powder as a binder, and molding the sheet into a sheet shape.

  A diffusion paper 5 for uniformly diffusing air into the positive electrode catalyst layer 4 is disposed on the inner surface of the bottom of the positive electrode case 1. For the diffusion paper 5, for example, craft paper can be used. The thickness of the diffusion paper 5 is desirably in the range of 50 to 100 μm. A water repellent film 6 having oxygen permeability is interposed between the diffusion paper 5 and the positive electrode catalyst layer 4. The water repellent film 6 is for preventing the alkaline electrolyte from leaking out from the air hole 3 of the positive electrode case 1. The water repellent film 6 can be formed from a fluororesin film such as a polytetrafluoroethylene film, for example. The water-repellent film 6 is not limited to a single sheet, and two or more sheets can be used in a stacked manner.

  The positive electrode current collector 7 is laminated on the positive electrode catalyst layer 4, and the peripheral edge thereof is in contact with the inner surface of the positive electrode case 1. Thereby, conduction between the positive electrode current collector 7 and the positive electrode case 1 is ensured. The positive electrode current collector 7 can be formed from, for example, a conductive porous plate such as a metal net.

  A separator 8 is laminated on the positive electrode catalyst layer 4. The separator 8 is formed of, for example, a microporous membrane made of polyolefin such as polypropylene and a nonwoven fabric. The microporous membrane is opposed to the positive electrode catalyst layer 4, and the nonwoven fabric is opposed to the gelled negative electrode 9. The microporous film is for preventing an internal short circuit due to precipitation of zinc oxide. It is mainly the nonwoven fabric that contributes to the retention of the alkaline electrolyte.

  The negative electrode case 10 serves as both a negative electrode current collector and a negative electrode terminal. The negative electrode case 10 has a bottomed cylindrical shape. As shown in FIG. 2, the negative electrode case 10 is formed of a plate material in which a base material 11 and a surface layer 12 made of at least one selected from the group consisting of Cu, In, Sn, Bi, and Zn are laminated. Yes.

  The surface layer 12 may be formed from a single metal of Cu, In, Sn, Bi, or Zn, or may be formed from an alloy containing these metals. Moreover, it is good also considering the multilayer board which laminated | stacked metal layers, such as Cu layer and Sn layer, alloy layers, or a metal layer and an alloy layer as a surface layer. Among these, a Sn metal layer and a Sn alloy layer are preferable. In this Sn alloy layer, the Sn content is 80% by mass or more, and the content of at least one additive metal element selected from the group consisting of Zn, Bi, Cu and In is 0.1% by mass or more, It is desirable to make it 20 mass% or less. A more preferable range is an Sn content of 85% by mass or more and an additive metal element content of 5% by mass or more and 15% by mass or less.

  The thickness of the surface layer 12 is desirably 3 μm or more and 40 μm or less. This is due to the reason explained below. When the thickness of the surface layer 12 is less than 3 μm, the base material 11 is more easily exposed when the surface layer 12 is eluted into the electrolytic solution. On the other hand, if the thickness of the surface layer 12 exceeds 40 μm, the sealing strength due to caulking and fixing may be reduced, and the occurrence of liquid leakage may be promoted. A more preferable range is 5 μm or more and 30 μm or less.

  As the base material 11, for example, a plate material in which a nickel layer and a stainless steel layer are laminated can be used. The nickel layer can be formed by plating or clad bonding. It is preferable to join the surface layer 12 described above to the surface of the stainless steel layer of the substrate 11. Therefore, it is desirable that the outer surface of the negative electrode case 10 be formed of a nickel layer. Examples of the method for joining the base material 11 and the surface layer 12 include plating and cladding processing.

  The thickness of the substrate 11 is desirably 50 μm or more and 150 μm or less. A more preferable range is 50 μm or more and 120 μm or less.

  The negative electrode case 10 is obtained, for example, by molding a plate material in which the base material 11 and the surface layer 12 are joined into a bottomed cylindrical shape by drawing so that the inner surface is constituted by the surface layer 12.

  Such a negative electrode case 10 is inserted into the positive electrode case 1 and functions as a sealing member. The gelled negative electrode 9 is accommodated in the negative electrode case 10 and is in contact with the inner surface (surface layer 12) of the negative electrode case 10.

  The gelled negative electrode 9 contains a non-catalyzed zinc alloy and an alkaline electrolyte. The gelled negative electrode 9 is formed, for example, by mixing non-hatched zinc alloy powder, an alkaline electrolyte, a thickener (gelling agent), and an inhibitor as necessary.

  Desirable zinc-free alloy is anhydrous zinc and lead-free zinc alloy. This zinc alloy desirably contains at least one selected from the group consisting of aluminum, bismuth and indium. Among such zinc-free zinc alloys, a zinc alloy having a Bi content of 50 to 1000 ppm, an In content of 100 to 1000 ppm, and at least one content selected from Al and Ca is preferably 10 to 100 ppm. A more preferable range of the Bi content is 100 to 500 ppm, a more preferable range of the In content is 300 to 700 ppm, and a more preferable range of at least one content selected from Al and Ca is 20 to 50 ppm. Moreover, it is desirable that the zinc-free zinc alloy is a powder having a particle size of about 100 to 300 μm.

  Examples of the alkaline electrolyte include an alkaline aqueous solution containing potassium hydroxide. The potassium hydroxide concentration in the alkaline electrolyte is preferably in the range of 30 to 45% by weight.

  As the thickening agent (gelling agent), those having a function of increasing the viscosity of the alkaline electrolyte to be gelled can be used. Examples of such a thickener include a water-absorbing polymer such as polyacrylic acid.

  Examples of the inhibitor include indium oxide, indium hydroxide, bismuth oxide and the like.

  The insulating gasket 13 has a ring shape. FIG. 3 shows a cross-sectional view obtained when the insulating gasket 13 is cut along the radial direction. As shown in FIG. 3, the insulating gasket 13 has an annular outer wall 14a and a folded portion 14b in which one open end of the outer wall 14a is folded inward. A frustoconical protrusion 14c is formed on the bottom surface of the folded portion 14b. The folded portion 14b rises in parallel with the outer wall 14a. On the inner surface of the other opening end of the outer wall 14a of the insulating gasket 13, a convex portion 15 is formed in an annular shape. Since the convex portion 15 can increase the compressive stress applied to the insulating gasket 13 when the open end portion 2 of the positive electrode case 1 is bent by caulking, the caulking strength can be improved.

  The insulating gasket 13 is made of nylon, for example, and the surface thereof is coated with a polyamide-based resin. The insulating gasket 13 formed from such a material can improve alkali resistance.

  As shown in FIGS. 1 and 2, the outer wall 14 a of the insulating gasket 13 is disposed between the outer peripheral surface of the negative electrode case 9 and the inner peripheral surface of the positive electrode case 1. Further, the folded portion 14b covers from the open end of the negative electrode case 9 to the inner peripheral edge. As shown in FIG. 3 described above, a protrusion 14c is formed on the bottom surface of the folded portion 14b. As shown in FIGS. 1 and 2, when the open end 2 of the positive electrode case 1 is bent by caulking, the folded portion 14 b is pushed upward by the projection 14 c, and the folded portion 14 b is brought into contact with the inner peripheral edge of the negative electrode case 10. Since it is pressed, the adhesion between the surface layer of the negative electrode case 10 and the insulating gasket 13 is improved. As a result, even if the surface layer 12 of the negative electrode case 10 elutes into the electrolyte due to high temperature storage or the like, the adhesion between the surface layer of the negative electrode case 10 and the insulating gasket 13 can be maintained. It is possible to improve the liquid leakage resistance during both overtime and overdischarge.

  When the width of the bottom surface of the folded portion 14b parallel to the radial direction of the insulating gasket 13 is W, the protrusion 14c is located in a region (including W / 2) from the folded portion 14b side to W / 2. It is desirable. At this position, the effect of the protrusion 14c pushing up the folded portion 14b is enhanced, so that the rate of occurrence of liquid leakage in a high temperature environment can be further reduced. The width W of the bottom surface of the folded portion 14b is parallel to the radial direction of the insulating gasket 13 and is equal to the distance from the outer peripheral surface of the outer wall 14a to the inner peripheral surface of the folded portion 14b.

  As shown in FIG. 8, it is possible to provide the protrusion 14c at a position exceeding W / 2 from the folded portion 14b side. However, the adhesiveness between the folded portion 14b and the negative electrode case 10 is lowered, which is a sufficient effect. There is a fear that you can not get.

  The width L of the protrusion 14c parallel to the radial direction of the insulating gasket 13 is desirably in the range of 10 to 60% of W. If the width L exceeds 60% of W, the effect of the protrusions may not be sufficiently obtained. On the other hand, if the width L is less than 10% of W, the portion facing the insulating gasket 13 through the separator 8 of the positive electrode 4 is excessively pressed, and the electrolyte solution may leak from the air holes 3 during overdischarge. There is.

  Specifically, the width W and the width L are measured by the following method. Disassemble any five batteries and remove the insulation gasket from each. Each insulating gasket is cut along the X axis and the Y axis that intersect perpendicularly at the center of the diameter, and is divided into four. The width W (distance between the outer peripheral surface of the outer wall 14a and the inner peripheral surface of the folded portion 14b) and the width L of each cut piece are measured using a tool microscope. As measurement results of the width W and the width L, 20 points are obtained. A width W and a width L for calculating the average of each are used.

(Second Embodiment)
FIG. 4 is an enlarged cross-sectional view showing a main part of an air zinc battery according to the second embodiment of the present invention, and FIG. 5 is obtained when the insulating gasket used in the air zinc battery of FIG. 4 is cut along the radial direction. FIG. 4 and 5, members similar to those described in FIGS. 1 to 3 are denoted by the same reference numerals, and description thereof is omitted.

  The air zinc battery according to the second embodiment has the same configuration as that of the air zinc battery according to the first embodiment except that the folded portion 14b of the insulating gasket 13 is inclined in a direction approaching the outer wall 14a. Have. With such a configuration, the adhesion between the folded portion 14b of the insulating gasket 13 and the inner peripheral edge of the negative electrode case 10 is improved, so that the air zinc has excellent leakage resistance during both overdischarge and high-temperature storage. A battery can be provided.

  In the first and second embodiments described above, the insulating gasket having the convex portion 15 is used. However, it is also possible to use an insulating gasket having no convex portion as illustrated in FIGS. 6 and 7. It is.

  In FIG. 1 to FIG. 7 described above, the shape of the protrusion 14c is a truncated cone shape, but it may be a columnar shape (column, prism), a conical shape, or a triangular pyramid shape. In order to reduce the influence on the positive electrode, it is desirable to have a truncated cone shape or a column shape.

[Example]
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings described above.

(Example 1)
A clad material having a thickness of 150 μm in which a 15 μm thick Sn plate (surface layer 12) was bonded to the SUS304 surface of a 135 μm thick SUS304 plate (base material 11) subjected to Ni plating was prepared. This was drawn into a bottomed cylindrical shape so that the inner surface was Sn metal.

  An insulating gasket 13 made of nylon and coated on the surface with a polyamide resin was prepared. The insulating gasket 13 has the structure shown in FIG. The position of the protrusion 14c was within the area (including W / 2) from the folded-back portion 14b side to W / 2 (W is 0.55 mm). Further, the width L of the protrusion 14c was a size corresponding to 40% of W. The thickness of the insulating gasket 13 was 0.20 mm where the convex portion 15 was not formed.

Further, indium oxide (In ₂ O ₃ ) as an inhibitor was mixed with a fine powder of polyacrylic acid as a gelling agent having a thickening action of the electrolytic solution until uniform, and stirred. Next, an unelectrolyzed zinc alloy powder containing 397 ppm Bi, 498 ppm In and 32 ppm Al and having an average particle size of 205 μm, an alkaline electrolyte composed of 30% KOH and 1% ZnO, polyacrylic acid and indium oxide Were added and mixed and stirred to prepare a gelled zinc negative electrode.

  After filling the gelled zinc negative electrode 9 thus obtained in the negative electrode case 10, it is fixed to the positive electrode case 1 in which the positive electrode catalyst layer 4 is accommodated by caulking, and the button of the JIS standard PR44 type having the structure shown in FIG. A zinc-air battery was manufactured.

(Example 2)
PR44 type having the structure shown in FIG. 1 described above in the same manner as in Example 1 except that a Sn—Zn alloy layer (Sn is 91 mass% and Zn is 9 mass%) is used instead of the Sn metal layer. A button-type zinc-air battery was manufactured.

(Example 3)
The figure described in the same manner as in Example 1 except that a Sn—Zn—Bi alloy (Sn is 89 mass%, Zn is 8 mass%, Bi is 3 mass%) is used instead of the Sn metal layer. A PR44 button-type zinc-air battery having the structure shown in FIG.

Example 4
Example 1 except that a Sn—Zn—In alloy (Sn is 91.5 mass%, Zn is 8 mass% and In is 0.5 mass%) is used instead of the Sn metal layer. Thus, a PR44 type button-type zinc-air battery having the structure shown in FIG. 1 was manufactured.

(Example 5)
A button-type zinc-air battery having the configuration described in Example 1 was manufactured except that an insulating gasket (shown in FIG. 5 described above) with the folded portion inclined toward the outer wall was used.

(Example 6)
A button-type zinc-air battery having the configuration described in Example 1 was manufactured except that an insulating gasket (shown in FIG. 6 described above) without the convex portion 15 was used.

(Example 7)
The button-type zinc-air battery having the configuration described in the above-described first embodiment except that an insulating gasket (shown in FIG. 7 described above) in which the folded portion is inclined toward the outer wall and does not have the convex portion 15 is used. Manufactured.

(Comparative example)
A PR44 type button-type zinc-air battery having the structure shown in FIG. 1 was manufactured in the same manner as in Example 1 except that no protrusion was provided on the bottom surface of the folded portion 14b of the insulating gasket 13.

  150 air zinc batteries obtained were prepared for each case, and the leakage rate after storage for 30 days, 60 days, 90 days, 120 days in an environment of 45 ° C.-95% RH, and 60 ° C.-95 The leakage occurrence rate after storage for 10 days, 20 days, 30 days, and 60 days in an environment of% RH was measured. Further, an overdischarge test with an overdischarge time of 100 hours was performed using a resistance of 250Ω under the condition of 25 ° C.-85% RH, and the rate of occurrence of liquid leakage from the air holes was measured. The results are shown in Table 1.

  As is clear from Table 1, the batteries of Examples 1 to 7 having protrusions on the bottom surface of the folded portion of the insulating gasket had a 95% relative humidity at 45 ° C and a 95% relative humidity at 45 ° C. In any environment, the rate of leakage was lower than that of the comparative example. Further, there was no overdischarge leakage rate.

  On the other hand, according to the comparative example having no protrusions, leakage occurred in storage for 60 days in an environment of 45% at 95% relative humidity, and leakage in storage for 10 days in an environment of 95% relative humidity at 60 ° C. Has resulted.

  Further, by comparing Examples 1 to 4, in Examples 2 to 4 in which the surface layer surface is formed of Sn alloy, the liquid leakage resistance at 60 ° C. is improved as compared with Example 1 in which the surface layer surface is formed of Sn. I understood it.

  In the above-described embodiments, examples of button-type zinc-air batteries have been described. However, the present invention is not limited to the above-described embodiments, and can take various forms without departing from the spirit of the invention. For example, a coin shape, a flat shape with a main surface or a quadrangular or substantially quadrangular shape can be used.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

1 is a cross-sectional view showing a zinc-air battery according to a first embodiment of the present invention. The principal part expanded sectional view which shows the air zinc battery of FIG. Sectional drawing obtained when the insulating gasket used for the air zinc battery of FIG. 1 is cut | disconnected along radial direction. The principal part expanded sectional view which shows the air zinc battery which concerns on the 2nd Embodiment of this invention. Sectional drawing obtained when the insulating gasket used for the air zinc battery of FIG. 4 is cut | disconnected along radial direction. Sectional drawing obtained when the insulating gasket used with the air zinc battery which concerns on 3rd Embodiment is cut | disconnected along radial direction. Sectional drawing obtained when the insulating gasket used with the air zinc battery which concerns on 4th Embodiment is cut | disconnected along radial direction. Sectional drawing obtained when the insulating gasket used with the air zinc battery which concerns on 5th Embodiment is cut | disconnected along radial direction.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Positive electrode case, 2 ... Upper end of opening, 3 ... Air hole, 4 ... Positive electrode catalyst layer, 5 ... Air diffusion paper, 6 ... Water-repellent film, 7 ... Positive electrode collector, 8 ... Separator, 9 ... Gel-like Zinc negative electrode, 10 ... negative electrode case, 11 ... base material, 12 ... surface layer, 13 ... insulating gasket, 14a ... outer wall of insulating gasket, 14b ... folded portion of insulating gasket, 14c ... projection of insulating gasket, 15 ... convex of insulating gasket 16, sealing tape.

Claims (3)

A negative electrode case having an inner surface of at least one surface selected from the group consisting of Cu, In, Sn, Bi and Zn;
In contact with the surface of the negative electrode case, a gelled negative electrode containing a zinc-free zinc alloy and an alkaline electrolyte;
A positive electrode case fixed by caulking to the negative electrode case;
An annular outer wall; and a folded portion in which one open end of the outer wall is folded inward, the outer wall being disposed between the outer surface of the negative electrode case and the inner surface of the positive electrode case, and the folded portion is A flat zinc battery comprising an insulating gasket covering the inner peripheral edge of the negative electrode case,
The flat type zinc battery, wherein the insulating gasket has a protrusion on a bottom surface of the folded portion.   2. The flat surface according to claim 1, wherein when the width of the bottom surface of the folded portion parallel to the radial direction of the insulating gasket is W, the protrusion is located in a region from the folded portion side to W / 2. Type zinc battery.   The flat zinc battery according to claim 1, wherein the folded portion rises in parallel with the outer wall or is inclined toward the outer wall.

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