WO2018123123A1

WO2018123123A1 - Alkali dry cell

Info

Publication number: WO2018123123A1
Application number: PCT/JP2017/027826
Authority: WO
Inventors: 嘉晃工藤
Original assignee: パナソニックＩｐマネジメント株式会社
Priority date: 2016-12-28
Filing date: 2017-08-01
Publication date: 2018-07-05
Also published as: JP2020030887A

Abstract

An alkali dry cell is provided with a cell case having an opening, a power generation element housed inside the cell case, and a sealing unit for sealing the opening. The sealing unit is provided with a negative electrode terminal board, a negative electrode current collector bonded to the negative electrode terminal board, and a gasket. The gasket is provided with a boss part that pierces through the negative electrode current collector, an outer periphery part that contacts the end part of the opening of the cell case, and a coupling part that couples the boss part and the outer periphery part. On an inner circumferential region adjacent to the boss part of the coupling part, there is a thin-walled part having an explosion proof function, the height of the boss part is 1.5-3.0 mm, and the difference between the inner diameter of the center part of the boss part and the minimum inner diameter of the upper and lower end parts is 0.03 mm or less.

Description

Alkaline battery

The present invention relates to an alkaline battery, and more particularly to a gasket structure provided in a sealing unit that seals an opening of a battery case.

Alkaline batteries include a battery case having an opening, a power generation element housed in the battery case, and a sealing unit that seals the opening of the battery case. The sealing unit includes a negative electrode terminal plate, a negative electrode current collector bonded to the negative electrode terminal plate, and a gasket. The gasket includes a boss portion that allows the negative electrode current collector to pass therethrough, an outer peripheral portion that is in contact with the opening end portion of the battery case, and a connecting portion that connects the boss portion and the outer peripheral portion. A thin wall portion having an explosion-proof function is formed in an inner peripheral region adjacent to the boss portion of the connecting portion.

If the battery is misused, the battery internal pressure may rise abnormally. When the battery internal pressure rises abnormally, the connecting portion swells toward the negative terminal plate, tension is applied to the thin portion, and the thin portion is broken. Thereby, the gas generated in the battery is discharged out of the battery through a gas vent hole formed in the negative electrode terminal plate. Therefore, the safety of the battery is ensured.

In order for the thin-walled portion to break, a space is required for the connecting portion to bulge toward the negative electrode terminal plate. However, when the battery is misused, if the battery temperature rises and the gasket softens, the softened boss may be pushed up toward the negative terminal plate against the frictional force with the negative electrode current collector. As a result, the distance between the connecting portion and the negative electrode terminal plate becomes short, and comes into contact with the negative electrode terminal plate before the connecting portion sufficiently swells, making it difficult to break the thin portion.

Patent Document 1 prevents the boss portion from being embedded in the flange portion by setting the ratio of the outer diameter of the boss portion of the gasket and the outer diameter of the flange portion of the negative electrode current collector to 4.0 or less. Yes. Thereby, the distance between the negative electrode terminal plate and the connecting portion of the gasket is maintained, and the connecting portion can sufficiently swell.

JP 2009-259533 A

In order to secure a sufficient space for the connecting portion to bulge toward the negative electrode terminal plate, it is desirable to limit the movement of the softened boss portion toward the negative electrode terminal plate. From the viewpoint of increasing the frictional force between the boss portion and the negative electrode current collector, it is considered that the larger the boss portion height of the gasket, the more advantageous. The height of the boss part is set to 5 mm or more, for example.

However, since a gasket for an alkaline battery is formed by resin injection molding, resin sinking inevitably occurs. The core pin that molds the hollow of the boss portion in the injection molding is cylindrical, but since the resin sink occurs, the inner diameter of the boss portion does not become constant. Usually, the inner diameter of the center part of the boss part becomes larger than the inner diameters of the upper and lower end parts of the boss part due to sink marks. For this reason, the coupling between the negative electrode current collector and the central portion of the boss part is considerably loosened, and the frictional force between the boss part and the negative electrode current collector tends to decrease.

One aspect of the present disclosure includes a battery case having an opening, a power generation element housed in the battery case, and a sealing unit that seals the opening. The sealing unit includes a negative electrode terminal plate, a negative electrode current collector bonded to the negative electrode terminal plate, and a gasket. The gasket includes a boss portion through which the negative electrode current collector passes, an outer peripheral portion in contact with an opening end portion of the battery case, and a connecting portion that connects the boss portion and the outer peripheral portion. The inner peripheral region adjacent to the boss portion of the connecting portion has a thin wall portion having an explosion-proof function, and the height of the boss portion is 1.5 mm or more and 3.0 mm or less, and the center of the boss portion It is related with the alkaline dry battery whose difference of the internal diameter of a part and the minimum internal diameter of the upper-lower-end part of the said boss | hub part is 0.03 mm or less.

The height of the boss part of the gasket is set to 3.0 mm or less, and the difference between the inner diameter of the central part of the boss part and the minimum inner diameter of the upper and lower end parts is set to 0.03 mm or less. The joint becomes stronger, the movement of the boss to the negative terminal plate side is restricted, and the explosion-proof function by the thin part of the gasket is stabilized. Further, since the volume of the entire gasket is reduced, more power generation elements can be accommodated in the battery case, and high capacity can be achieved.

FIG. 1A is a sectional view showing a general mold B for manufacturing a gasket. FIG. 1B is a cross-sectional view showing a gasket manufactured with the mold of FIG. 1A. FIG. 2A is a cross-sectional view showing an improved mold B for manufacturing a gasket. FIG. 2B is a cross-sectional view showing a gasket manufactured with the mold of FIG. 2A. FIG. 3A is a plan view of a gasket in which ribs are formed on the opening-side surface of the connecting portion. 3B is a cross-sectional view of the gasket of FIG. 3A taken along line IIIB-IIIB. FIG. 4 is a half sectional view showing an example of the internal structure of the alkaline dry battery according to the embodiment of the present invention. FIG. 5 is a partial cross-sectional view showing an example of the structure of the sealing unit according to the embodiment of the present invention.

The alkaline dry battery according to an embodiment of the present invention includes a battery case having an opening, a power generation element housed in the battery case, and a sealing unit that seals the opening of the battery case. The sealing unit includes a negative electrode terminal plate, a negative electrode current collector bonded to the negative electrode terminal plate, and a gasket. The gasket includes a boss portion that penetrates the negative electrode current collector, an outer peripheral portion that is in contact with an end portion of the opening of the battery case, and a connecting portion that connects the boss portion and the outer peripheral portion. A thin wall portion having an explosion-proof function is formed in an inner peripheral region adjacent to the boss portion of the connecting portion.

Here, the height of the boss portion is 1.5 mm or more and 3.0 mm or less, and the difference between the inner diameter of the central portion of the boss portion and the minimum inner diameter of the upper and lower ends of the boss portion (hereinafter referred to as an inner diameter difference ΔD). ) Is limited to 0.03 mm or less. By limiting the height of the boss part to 3.0 mm or less and limiting the inner diameter difference ΔD to 0.03 mm or less, the boss part and the negative electrode current collector are firmly joined, and even if the gasket is softened, the boss part Movement to the negative terminal plate side is restricted. The upper and lower end portions of the boss portion correspond to both end portions of the boss portion in the height direction of the alkaline dry battery. Whichever may be considered as the upper end or the lower end, in the following illustrated example, the side on which the negative electrode terminal plate is disposed is the upper end.

The inner diameter at the center of the boss is the inner diameter at the center in the height direction of the boss (that is, half height). The inner diameter of the boss portion is usually minimized in the vicinity of the upper end portion or the lower end portion of the boss portion. In addition, in the gasket formed by resin injection molding, an annular protrusion due to the gate portion of the mold may be formed on the inner peripheral edge of the end surface of the boss portion. In this case, what is necessary is just to measure the height which excluded the annular protrusion at the intermediate point between the inner wall and the outer wall of the boss part.

The upper end portion of the boss portion is a region 30% of the height of the boss portion from the upper end surface of the boss portion, and the lower end portion of the boss portion is 30% of the height of the boss portion from the lower end surface of the boss portion. It is an area. That is, both end portions excluding the central region 40% of the boss portion are upper and lower end portions of the boss portion.

When the height of the boss portion is set to 3.0 mm or less, resin sink is less likely to occur, so that the inner diameter difference ΔD can be easily limited to 0.03 mm or less. On the other hand, when the height of the boss part exceeds 3 mm, it is generally difficult to reduce the inner diameter difference ΔD to 0.03 mm or less. For example, if the height of the boss part is 5 mm or more, the inner diameter difference ΔD exceeds 0.05 mm.

The height of the boss may be 3.0 mm or less, but is preferably 2.5 mm or less from the viewpoint of reducing the entire gasket volume as much as possible and accommodating more power generation elements in the battery case. 0.0 mm or less is more preferable. However, if the height of the boss part is smaller than 1.5 mm, the frictional force between the boss part and the negative electrode current collector is drastically reduced, and the movement of the boss part toward the negative electrode terminal plate is limited when the gasket is softened. It becomes difficult.

In injection molding, the inner diameter difference ΔD can be more easily limited to 0.03 mm or less by slightly narrowing the central portion of the cylindrical core pin that molds the hollow of the boss portion. From the viewpoint of making the inner diameter difference ΔD as close to 0 as possible, it is preferable that the central portion of the core pin is made 0.3% to 2.0% smaller than the maximum diameter of the core pin. Even when the center portion of the core pin is thinned, the inner diameter D _{c of the} center portion and the minimum inner diameter D _t of the upper end portion and the lower end portion of the boss portion often satisfy the relationship of D _c > D _t , but D _c ≦ the relationship of D _t may be satisfied. From the viewpoint of further strengthening the combination of the boss portion and the negative electrode current collector, the inner diameter difference ΔD is preferably 0.02 mm or less, and more preferably 0.01 mm or less.

A rib (hereinafter referred to as a reinforcing rib) extending from the boss portion side to the outer peripheral portion side may be formed on the opening-side surface of the gasket connecting portion. Thereby, the structural strength of the gasket is increased, and when the gasket is softened, the movement of the boss portion toward the negative electrode terminal plate is easily restricted. A plurality of reinforcing ribs are preferably formed. At this time, the plurality of reinforcing ribs are preferably formed so as to divide the opening-side surface of the connecting portion into two or more regions, and the sizes of the two or more regions are preferably equal. For example, two reinforcing ribs may be formed so as to divide the opening-side surface of the connecting portion into two equal parts, and three or four such that the opening-side surface of the connecting portion is divided into three equal parts or four equal parts. The reinforcing ribs may be formed radially.

The angle (hereinafter referred to as the skirt angle) θ formed by the opening side surface of the inner peripheral region of the connecting portion and the height direction of the boss portion is preferably 45 degrees or more. The greater the skirt angle θ, the greater the resistance when the boss moves to the negative terminal plate side when the gasket is softened. The skirt angle θ is more preferably 50 degrees or more, and may be 90 degrees or more. However, the upper limit of the skirt angle θ is about 130 degrees, preferably 120 degrees or less, from the viewpoint of stabilizing the explosion-proof function due to the thin-walled portion of the gasket. When the skirt angle θ exceeds 130 degrees, it may be difficult to secure a space for the connecting portion to sufficiently swell.

In the completed battery, various stresses are applied to the gasket. Therefore, it is difficult to accurately measure the inner diameter of the boss portion even if the cross section of the battery is CT scanned to take a cross-sectional photograph. Then, the internal diameter of the boss | hub part of the gasket in the completed battery is measured in the following procedures.

First, disassemble the battery, take out the sealing unit, and remove the negative terminal plate welded to the negative electrode current collector. Next, the negative electrode current collector is pulled out from the boss portion of the gasket. When a sealant is interposed between the negative electrode current collector and the inner wall of the boss, the tip of the negative electrode current collector is heated at 70 ° C. for 3 seconds to soften the sealant, and then the negative electrode current collector is removed. Just pull it out. The gasket thus isolated is placed in a constant temperature bath at 35 ° C. and a relative humidity of 90% and left for 24 hours. Accordingly, the gasket is heated and humidified under mild conditions, the residual stress of the gasket is released, and the state of the gasket before the sealing unit is assembled is reproduced. Thereafter, a cross-sectional photograph of the boss part may be taken by CT scan, and the inner diameter of each part may be measured.

Hereinafter, embodiments of the present invention will be further described with reference to the drawings. In addition, this invention is not limited to the following embodiment.

First, a general mold for manufacturing a gasket will be described. FIG. 1A is a cross-sectional view showing an example of a general mold structure. The mold includes an upper mold 11 </ b> A, a lower mold 11 </ b> B, and a cylindrical core pin 13. The diameter of the portion that molds the hollow of the boss portion of the core pin 13 is constant. When the lower mold 11B is engaged with the upper mold 11A, the boss part forming space part 14, the connecting part forming space part 16, and the outer peripheral part forming space part 17 are located between the upper mold 11A and the lower mold 11B. It is formed. The height H ₀ of the boss forming space 14 is designed to be 5 mm or more. The core pin 13 is inserted from a through hole provided in the lower mold 11B, and is arranged so as to be planted in the center of the boss portion forming space portion 14. The upper mold 11 </ b> A is formed with a gate portion 12 that opens toward the end of the core pin 13. The molten resin is injected from the gate portion 12 and filled in the order of the boss portion forming space portion 14, the connecting portion forming space portion 16, and the outer peripheral portion forming space portion 17.

FIG. 1B is a cross-sectional view showing an example of a gasket manufactured using a general mold as described above. The gasket 7 includes a cylindrical boss portion 7a having a hollow 13h into which the negative electrode current collector 6 is inserted, an outer peripheral portion 7b in contact with the opening end of the battery case, and a connecting portion that connects the boss portion 7a and the outer peripheral portion 7b. 7c.

The mold as described above causes considerable resin sink because the diameter of the core pin 13 is constant in addition to the height of the boss forming space 14 being large. Therefore, the inner diameter of the central portion of the boss portion 7a becomes 0.05 mm or more larger than the minimum inner diameter of the upper and lower end portions due to resin sink. The gasket 7 is formed with an annular protrusion 7e corresponding to the gate portion 12 on the inner peripheral edge of the end surface of the boss portion 7a. The height H ₀ of the boss portion 7a excluding the annular protrusion 7e corresponds to the height of the boss portion forming space portion 14 and is 5 mm or more. Therefore, it can also hinder further increase in capacity of the battery.

On the other hand, FIG. 2A is a cross-sectional view showing an example of an improved mold structure. FIG. 2B shows a cross-sectional view of an example of a gasket manufactured with an improved mold. Components corresponding to those in FIGS. 1A and 1B are denoted by the same reference numerals.

The height H ₁ of the improved boss forming space 14 of the mold is designed to be 1.5 mm or more and 3.0 mm or less. The core pin 13 has a substantially cylindrical shape with a central portion slightly narrower than the upper and lower end portions.

Boss portion 7a of the gasket 7 which is molded in an improved mold, the height H ₁ excluding the annular projection 7e is, corresponding to the height of the boss portion forming the space portion 14, 1.5 mm or more, 3. 0 mm or less. Further, the difference ΔD between the inner diameter of the central portion of the boss portion 7a and the minimum inner diameter of the upper and lower end portions can be easily limited to 0.03 mm or less.

In the case of the illustrated example, the skirt angle θ is formed by the surface on the opening side of the thin portion 8 in the cross section of the gasket and the region on the lower side (power generation element side) side of the connecting portion 7c of the peripheral surface of the boss portion 7a. It is calculated as an angle.

FIG. 3A shows a plan view of another example of a gasket manufactured with an improved mold. FIG. 3B is a sectional view of the gasket taken along line IIIB-IIIB. In the gasket, four reinforcing ribs 7d are radially formed on the opening-side surface of the connecting portion. In FIG. 3B, the difference in the inner diameter of the boss portion 7a is emphasized. It is shown that the inner diameter of the central portion is the largest, and the upper end portion and the lower end portion each have a minimum diameter.

FIG. 4 is a half sectional view showing an example of the internal structure of the alkaline dry battery according to the embodiment of the present invention. FIG. 5 is a partial cross-sectional view showing an example of the structure of the sealing unit according to the embodiment. In the bottomed cylindrical battery case 1, a positive electrode 2 and a gelled negative electrode 3 are accommodated via a separator 4. The battery case 1 is obtained, for example, by press-molding a nickel-plated steel sheet into a predetermined shape. A conductive film may be formed on the inner surface of the battery case 1.

The opening of the battery case 1 is sealed with a sealing unit 9 in which a negative electrode terminal plate 5, a negative electrode current collector 6, and a gasket 7 are assembled together. The negative electrode terminal plate 5 is obtained, for example, by press-molding a nickel-plated steel plate or a tin-plated steel plate into a predetermined shape. The peripheral edge of the negative electrode terminal plate 5 is provided with a gas vent hole (not shown) for releasing gas to the outside when the explosion-proof function by the thin portion 8 of the gasket 7 is activated. A flange 6 a is formed at the end of the negative electrode current collector 6, and the flange 6 a is joined to the negative terminal plate 5 by welding. The negative electrode current collector 6 is obtained, for example, by pressing a brass wire into a nail shape having a predetermined dimension. The outer peripheral surface of the battery case 1 is covered with an exterior label 10.

The negative electrode current collector 6 passes through the boss portion 7a of the gasket 7. The outer peripheral portion 7 b of the gasket is in contact with the opening end portion of the battery case 1 and is caulked on the peripheral edge of the negative electrode terminal plate 5. An annular connecting portion 7c that connects the boss portion 7a and the outer peripheral portion 7b has a thin-walled portion 8 having an explosion-proof function in the inner peripheral region near the boss portion 7a. The minimum thickness in the thin portion 8 is set to, for example, 0.10 mm to 0.35 mm. As the material of the gasket 7, for example, a polyamide resin such as 6,6-nylon is used.

The inner diameter and outer diameter of the boss 7a can be tightened to such an extent that alkaline electrolyte does not leak when the negative electrode current collector 6 is fixed through the hollow 13h (FIG. 2B), and the boss 7a. Designed to prevent cracking. From the above viewpoint, the ratio (D _i / D _c ) between the body diameter (D _i ) of the negative electrode current collector 6 and the inner diameter (D _c ) of the central portion of the boss portion 7a is, for example, 1.02 ≦ D _i / D _c ≦ 1.20 is set.

The body diameter of the negative electrode current collector 6 is preferably 2.0 mm or less, and more preferably 1.8 mm or less, for example. In addition, from the viewpoint of ensuring excellent current collecting property, the trunk diameter of the negative electrode current collector 6 is preferably 1.1 mm or more, and more preferably 1.15 mm or more.

The outer diameter of the boss is preferably 3.0 mm to 4.5 mm, for example. The outer diameter of the outer peripheral portion 7b of the gasket is determined by the battery size.

When the boss portion 7a and the negative electrode current collector 6 are strong, the frictional force between the boss portion 7a and the negative electrode current collector 6 can be sufficiently ensured. Therefore, the surface roughness (R _max ) of the negative electrode current collector 6 is For example, it may be 0.3 to 3.0 μm. On the surface of the negative electrode current collector 6, tin may be formed a plating layer such as indium, but since it is small surface roughness (R _max) is, may not form a plating layer.

The negative electrode current collector 6 is made of brass, but the copper content of brass may be reduced. For example, when the copper content of brass is 50 to 60% by mass or less, the electrical conductivity of the negative electrode current collector 6 decreases, and the heat generation of the negative electrode current collector increases when the battery is misused. Even in such a case, since the coupling between the boss portion 7a and the negative electrode current collector 6 is strong, the movement of the boss portion toward the negative electrode terminal plate is sufficiently limited.

A sealant may be interposed between the negative electrode current collector and the boss portion. The sealant makes it difficult for leakage of the alkaline electrolyte from between the negative electrode current collector and the boss portion. As the sealant, a silicone resin, a fluororesin, an epoxy resin to which polyamidoamine is added, or the like can be used.

The type of the alkaline battery is not particularly limited. In particular, in the embodiment of the single-type battery, single-type battery, single-size battery, or single-type battery, which tends to generate heat due to misuse, the above-described sealing unit is used. The effect of stabilizing the explosion-proof function is increased.

Hereinafter, the specific configuration of the power generation element of the alkaline dry battery will be further described.

For the positive electrode 2, for example, a molded body of a mixture containing a positive electrode active material, a conductive agent, and an alkaline electrolyte is used. A binder such as polyethylene powder and a lubricant such as stearate may be added to the mixture. As the positive electrode active material, manganese dioxide powder, nickel oxyhydroxide powder, or the like is used. For the conductive agent, graphite powder or the like is used.

For the gelled negative electrode 3, for example, a mixture containing a negative electrode active material, an alkaline electrolyte, and a gelling agent is used. Zinc alloy powder is used for the negative electrode active material. As the gelling agent, sodium polyacrylate or the like is used. In order to improve the corrosion resistance of the zinc alloy, a metal compound having high hydrogen overvoltage such as indium or bismuth or a surfactant may be added to the mixture.

For the separator 4, for example, a nonwoven fabric mainly composed of polyvinyl alcohol fiber and rayon fiber is used.

The positive electrode 2, the gelled negative electrode 3 and the separator 4 each contain an alkaline electrolyte. As the alkaline electrolyte, for example, an aqueous solution containing 30 to 40% by mass of potassium hydroxide and 1 to 3% by mass of zinc oxide is used.

Hereinafter, although embodiments of the present invention will be further described based on examples, the present invention is not limited to the examples. Here, an AAA alkaline battery having a structure as shown in FIG. 4 was produced.

Example 1
(1) Production of Sealing Unit Gasket 7 was produced by injection molding 6,6-nylon into a predetermined shape using a plurality of types of molds. The height H of the boss portion 7a of the gasket 7 and the difference ΔD between the inner diameter of the central portion of the boss portion 7a and the minimum inner diameter of the upper and lower end portions were changed as shown in Table 1.

In all the gaskets 7, the inner diameter D _{c at} the center of the boss 7 a and the minimum inner diameter D _{t at} the upper and lower ends of the boss 7 a satisfied the relationship of D _c > D _t . The target of the inner diameter of the central portion of the boss portion 7a of the gasket 7 was set to 1.10 mm. No reinforcing ribs were formed on the opening-side surface of the connecting portion 7c of the gasket 7. The skirt angle θ was 45 degrees.

A negative electrode current collector 6 was produced by processing brass having a copper content of 58 mass% into a nail shape having a total length of 30 mm and a body diameter of 1.20 mm. A plating layer was not formed on the surface of the negative electrode current collector 6, and the surface roughness (R _max ) was 1.0 μm. On the other hand, a negative electrode terminal plate 5 was produced by pressing a nickel-plated steel plate having a thickness of 0.4 mm into a predetermined shape, and the flange portion 6 a of the negative electrode current collector 6 was welded to the negative electrode terminal plate 5. Then, the negative electrode current collector 6 was press-fitted into the hollow 13 h of the boss 7 a of the gasket 7 to assemble the sealing unit 9.

(2) Production of positive electrode Electrolytic manganese dioxide powder having an average particle diameter of 35 μm and graphite powder having an average particle diameter of 15 μm are mixed at a mass ratio of 94: 6, and 2 parts by mass of alkaline electrolyte is added to 100 parts by mass of the mixture. After sufficiently stirring, compression molding was performed to obtain a flaky positive electrode mixture. The flaky positive electrode mixture was pulverized into granules and then pressure-molded into hollow cylindrical pellets.

As the alkaline electrolyte, an aqueous solution containing 35% by mass of potassium hydroxide and 2% by mass of zinc oxide was used.

(3) Preparation of negative electrode A gelling agent (sodium polyacrylate powder), an alkaline electrolyte, and a zinc alloy powder having an average particle size of 160 μm were mixed at a mass ratio of 0.8: 33.6: 65.6. A gelled negative electrode 3 was obtained.

(4) Battery assembly The positive electrode 2 was inserted into the battery case 1, and the positive electrode 2 was brought into close contact with the inner wall of the battery case 1 with a pressing jig. A bottomed cylindrical separator 4 is disposed in the hollow of the positive electrode 2. For the separator 4, a nonwoven fabric mainly composed of polyvinyl alcohol fiber and rayon fiber was used. After the alkaline electrolyte was injected into the separator 4 and a predetermined time had elapsed, the gelled negative electrode 3 was filled into the separator 4. The outer peripheral part of the gasket of the sealing unit was disposed in the vicinity of the opening of the battery case 1, and the opening end of the battery case 1 was folded inward to seal it, thereby completing the battery.

<Short-circuit test>
A plurality of 120 alkaline batteries each having a different configuration of the boss portion 7a of the gasket 7 as shown in Table 1 were prepared, and 30 sets each including four batteries connected in series were produced. At normal temperature (20 ° C.), 30 sets of batteries were left in a closed circuit state for 24 hours, then returned to an open circuit state and left for one week. Table 1 shows the percentage of sets in which any of the four batteries were damaged without the explosion-proof function being activated.

Example 2
The length of the boss portion 7a is the same as that of the first embodiment except that two or four reinforcing ribs 7d extending from the boss portion side to the outer peripheral portion side are formed on the opening side surface of the coupling portion 7c of the gasket 7. A battery including a gasket 7 having a diameter of 1.5 mm and an inner diameter difference ΔD of 0.03 mm was produced.

<Severe short circuit test>
120 pieces of alkaline batteries having different gaskets 7 as shown in Table 2 were prepared, and 30 sets of 4 batteries connected in series were prepared. 30 sets of batteries were stored in a constant temperature bath at 60 ° C. for 8 hours, then left at 60 ° C. in a closed circuit state for 24 hours, then returned to an open circuit state and left for 1 week. Table 2 shows the percentage of sets in which any of the four batteries were damaged because the explosion-proof function did not work.

Example 3
A battery comprising a gasket 7 having a boss 7a length of 1.5 mm and an inner diameter difference ΔD of 0.03 mm, as in Example 1, except that the skirt angle of the gasket 7 was changed as shown in Table 3. This was prepared and subjected to a severe short-circuit test at 60 ° C. as in Example 2. The results are shown in Table 3.

As described above, it was shown that the explosion-proof function is stabilized by setting the height of the boss portion 7a to 1.5 mm or more and 3.0 mm or less and limiting the inner diameter difference ΔD to 0.03 mm or less. Further, it was shown that the explosion-proof function is stabilized even in a harsher environment by providing the gasket 7 with the reinforcing rib 7d or increasing the skirt angle.

The alkaline dry battery according to the embodiment of the present invention is useful as a power source for various electronic devices because it has an excellent explosion-proof function and can be increased in capacity.

1: battery case 2: positive electrode 3: gelled negative electrode 4: separator 5: negative electrode terminal plate 6: negative electrode current collector 6a: flange portion 7: gasket 7a: boss portion 7b: outer peripheral portion 7c: connecting portion 7d: rib 7e: annular Protrusion 8: Thin portion 9: Sealing unit 10: Exterior label 11A: Upper die 11B: Lower die 12: Gate portion 13: Core pin 13h: Hollow 14: Boss portion forming space portion 16: Connection portion forming space portion 17: Outer periphery Part formation space

Claims

A battery case having an opening;
A power generation element housed in the battery case;
A sealing unit for sealing the opening,
The sealing unit includes a negative electrode terminal plate, a negative electrode current collector bonded to the negative electrode terminal plate, and a gasket.
The gasket includes a boss portion that penetrates the negative electrode current collector, an outer peripheral portion that is in contact with an opening end portion of the battery case, and a connecting portion that connects the boss portion and the outer peripheral portion.
In the inner peripheral area adjacent to the boss part of the connecting part, it has a thin part having an explosion-proof function,
The height of the boss is 1.5 mm or more and 3.0 mm or less,
The alkaline dry battery in which the difference between the inner diameter of the central portion of the boss portion and the minimum inner diameter of the upper and lower end portions of the boss portion is 0.03 mm or less.
The alkaline dry battery according to claim 1, wherein a rib extending from the boss portion side to the outer peripheral portion side is formed on a surface of the connecting portion on the opening side.
The alkaline dry battery according to claim 2, wherein the plurality of ribs are formed so as to divide the opening-side surface of the connecting portion into two or more regions.
The alkali according to any one of claims 1 to 3, wherein an angle θ formed by a surface on the opening side of the inner peripheral region of the connecting portion and a height direction of the boss portion is 45 degrees or more. Dry cell.