Alkaline batteries

Abstract

To suppress liquid leakage in an alkaline dry battery, over a long period of time.SOLUTION: An alkaline dry battery includes a battery case having an opening, an electric-power-generating element housed in the battery case, and a sealing unit sealing the opening. The sealing unit includes a negative electrode terminal plate, a nail-shaped negative electrode current collector, and a gasket. The negative electrode current collector includes a flange part having a joint surface joined to the negative electrode terminal plate, and a columnar trunk part. The gasket includes a boss part having a through hole penetrating through the trunk part, an outer peripheral part in contact with an opening end portion of the battery case, and a linking part linking between the boss part and the outer peripheral part. A first sealant is interposed between an inner peripheral surface of the through hole in the boss part and an outer peripheral surface of the trunk part of the negative electrode current collector, and a second sealant is interposed between an end face, of the boss part, facing the flange part and a rear face of the joint surface of the flange part. The first and second sealants contain polyamide, and the amine value A1 of the first sealant and the amine value A2 of the second sealant satisfy A1<A2.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to an alkaline dry battery.

Background Art

[0002] Patent Document 1 proposes an "alkaline battery in which a positive electrode mixture, a negative electrode gel, a separator, and an electrolytic solution are housed in a bottomed cylindrical battery case having a positive electrode at the bottom, and an opening at the end opposite to the bottom is sealed by a negative electrode terminal plate to which a negative electrode current collector is connected and a gasket, wherein the negative electrode current collector is fixed to the negative electrode terminal plate and has an annular groove portion that is open at the bottom side and recessed toward the negative electrode terminal plate side, and a shaft portion whose inner portion surrounded by the annular groove portion extends toward the bottom side, and the extending end side of the shaft portion is inserted into the negative electrode gel, the gasket is made of a synthetic resin molding material, and has a tubular portion provided with a hollow portion into which the shaft portion of the negative electrode current collector is press-fitted, and a partition portion that seals between the outer periphery of the tubular portion and the periphery of the negative electrode terminal plate and the opening to separate the inside of the battery case, and the end of the tubular portion on the negative electrode terminal plate side is fitted into the annular groove portion".

[0003] Patent Document 2 describes a method for manufacturing a cylindrical battery, in which an electrolyte is filled into a bottomed cylindrical battery can with the bottom facing downwards, and an electrode terminal plate is fitted into the opening of the battery can via a sealing gasket, the electrode terminal plate being a resin disc with a hollow cylindrical boss portion formed in the center with the axis in the vertical direction, wherein the cylindrical battery comprises a current collector having a disc-shaped head formed at the upper end of a body that extends vertically in a rod-like shape, the upper end side of the body of the current collector being press-fitted into an insertion hole formed in the center of the boss portion, the upper surface of the head being attached to the lower surface of the electrode terminal plate, and a recess formed on the upper surface of the boss portion that expands in diameter to open upward so as to be coaxial with the insertion hole, the recess being formed between the upper surface of the boss portion and the head of the current collector The invention proposes a method for manufacturing a cylindrical battery, characterized in that the recess is not closed by the lower surface and a sealant fills the inside of the recess, and the manufacturing method includes a sealant application step of applying the sealant below the head of the current collector and a press-fitting step of press-fitting the current collector, which is welded to the electrode terminal plate, into the boss portion from above, wherein in the sealant application step, the sealant is applied to the surface of a belt that moves in the longitudinal direction and the body of the current collector is pressed against the surface of the belt, and in the press-fitting step, the sealant applied to the current collector is scraped off at the upper edge of the insertion hole in the boss portion and the inside of the recess is filled with the scraped-off sealant.

[0004] Patent Document 3 states that "the sealing agent interposed between the cathode sealing plate, which has a copper layer as its innermost layer, and the insulating packing is a fatty acid polyamidoamine represented by the general formula H2N-[R1-NHCO-R2-CONH-(R1-NH-)aR1]bNH2 [where R1 is (CH2)] n The polymethylene group or (CH2) shown l O(CH2CH2O) m (CH2) l This is a polyether group represented by (CH)i(CH2)j(CH3) k The present invention proposes an alkaline battery characterized by the hydrocarbon chain of a higher fatty acid, represented by [a, b, l, m, n, i, j, k] being an integer from 1 to 30, and having an amine value of 50 to 500.

[0005] Patent document 4 proposes an alkaline battery in which a polyamidoamine is interposed between the cathode sealing plate and the gasket, and the number-average molecular weight of the polyamidoamine is 60 to 6000. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Patent No. 7122117 [Patent Document 2] Patent No. 6741422 [Patent Document 3] Special Publication No. 63-033263 [Patent Document 4] Japanese Patent Application Publication No. 58-019854 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] There is a growing demand for extending the recommended use-by date of alkaline batteries. For example, extending the recommended use-by date as much as possible is necessary to improve the reliability of emergency power sources during disasters. To achieve this, it is important to suppress leakage due to creep. Creep is the phenomenon in which alkaline electrolyte rises up the surface of charged metal. Creep is accelerated in high temperature and high humidity environments.

[0008] An alkaline dry cell comprises a battery case with 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 comprises a negative electrode terminal plate, a negative electrode current collector joined to the negative electrode terminal plate, and a gasket. The negative electrode current collector is inserted into the negative electrode which contains a large amount of alkaline electrolyte. Leakage occurs due to a creep phenomenon in which the alkaline electrolyte creeps up the surface of the charged negative electrode current collector and passes through the gap between the gasket and the negative electrode current collector. [Means for solving the problem]

[0009] 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 for sealing the opening. The power generation element includes a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode. The sealing unit includes a negative electrode terminal plate, a nail-shaped negative electrode current collector, and a gasket. The negative electrode current collector includes a flange portion having a joint surface joined to the negative electrode terminal plate and a columnar body portion. The gasket includes a boss portion having a through hole penetrating the body portion, an outer peripheral portion contacting an opening end portion of the battery case, and a connecting portion connecting the boss portion and the outer peripheral portion. A first sealant is interposed between an inner peripheral surface of the through hole of the boss portion and an outer peripheral surface of the body portion of the negative electrode current collector. A second sealant is interposed between an end surface of the boss portion facing the flange portion and a back surface of the joint surface of the flange portion. The first sealant and the second sealant contain polyamide, and an amine value A1 of the first sealant and an amine value A2 of the second sealant satisfy A1 < A2. This relates to an alkaline dry battery.

Effects of the Invention

[0010] According to the present disclosure, leakage of an alkaline dry battery in a high-temperature and high-humidity environment is suppressed.

Brief Description of the Drawings

[0011] [Figure 1] It is a semi-cross-sectional view showing an example of the internal structure of an alkaline dry battery according to an embodiment of the present disclosure. [Figure 2] It is an enlarged cross-sectional view of a main part of FIG. 1.

Modes for Carrying Out the Invention

[0012] The embodiments of this disclosure will be described below with examples, but this disclosure is not limited to the examples described below. In the following description, specific numerical values, materials, etc. may be given as examples, but other numerical values, materials, etc. may be applied as long as the effects of this disclosure are obtained. In addition, components other than those characteristic of this disclosure may be replaced with components of known batteries. In this specification, when "range of numerical value A to numerical value B" is used, the range includes numerical values ​​A and B. For example, "A to B mol%" is synonymous with "A mol% or more and B mol% or less". In the following description, when lower and upper limits of numerical values ​​relating to specific physical properties or conditions are given as examples, either of the given lower limits and either of the given upper limits may be arbitrarily combined as long as the lower limit does not exceed the upper limit. When multiple materials are given as examples, one of them may be selected and used alone, or two or more may be used in combination.

[0013] Furthermore, this disclosure encompasses any combination of matters described in two or more claims, which may be arbitrarily selected from the multiple claims set forth in the attached claims. In other words, any combination of matters described in two or more claims, which may be arbitrarily selected from the multiple claims set forth in the attached claims, is possible, provided that no technical inconsistency arises.

[0014] The type of alkaline battery relating to this disclosure is not particularly limited and may be any of the sizes from D to AAA, or other types.

[0015] An alkaline dry cell according to one embodiment of the present disclosure comprises a battery case having an opening, a power generation element housed within the battery case, and a sealing unit that seals the opening of the battery case. The power generation element has a positive electrode, a negative electrode, and a separator interposed between the positive and negative electrodes. The positive electrode, negative electrode, and separator are impregnated with an alkaline electrolyte. The battery case is typically cylindrical and has a cylindrical portion and a bottom portion.

[0016] The sealing unit includes a negative electrode terminal plate, a nail-shaped negative electrode current collector, and a gasket. The negative electrode terminal plate closes the opening of the battery case and functions as a negative electrode terminal. The negative electrode terminal plate usually has a gas vent hole for discharging gas to the outside when the internal pressure of the battery rises above a certain level. The negative electrode current collector includes a flange portion having a joint surface joined to the negative electrode terminal plate and a columnar body portion.

[0017] The gasket includes a boss portion having a through hole penetrating the body portion, an outer peripheral portion contacting the opening end portion of the battery case, and a connecting portion connecting the boss portion and the outer peripheral portion. The connecting portion may have a thin portion having an explosion-proof function. The thin portion breaks when the internal pressure of the battery rises above a certain level. In that case, the gas is discharged to the outside through the gas vent hole.

[0018] A first sealant is interposed between the inner peripheral surface of the through hole of the boss portion and the outer peripheral surface of the body portion of the negative electrode current collector (hereinafter, also referred to as "the inner hole sealing portion"). The first sealant suppresses the phenomenon that the alkaline electrolyte climbs up the body portion of the charged negative electrode current collector.

[0019] A second sealant is interposed between the end surface of the boss portion facing the flange portion of the negative electrode current collector and the back surface of the joint surface of the flange portion (hereinafter, also referred to as "the outer end surface of the boss portion"). The second sealant suppresses the further diffusion of the alkaline electrolyte that has reached the outer end surface of the boss portion to the outside, despite the suppressing action of the first sealant. If the second sealant does not exist, a small amount of alkaline electrolyte that has reached the outer end surface of the boss portion may further diffuse on the inner surface of the negative electrode terminal plate and pass through the gas vent hole to reach the outer surface of the negative electrode terminal plate.

[0020] The first sealant and the second sealant contain polyamide. Polyamide is a general term for resins or polymers having a polyamide structure. The polyamide structure has a repeating structure of amide bonds.

[0021] The polyamide may have a structure other than the polyamide structure. Such resins are also collectively referred to as polyamide-based resins. The polyamide-based resin may be, for example, an epoxy-added polyamide. The epoxy-added polyamide is, for example, a reaction product of an epoxy resin and a polyamide amine. As the epoxy resin to be added to the polyamide amine, for example, bisphenol A type epoxy resin can be used. Also, the polyamide may be a polyamide amine diluted with a solvent.

[0022] However, the polyamide contained in the first sealant and the second sealant is a polyamide amine having an amine value described below.

[0023] The amine value A1 of the first sealant and the amine value A2 of the second sealant satisfy A1 < A2. The polyamide amine has the effect of physically suppressing the creep phenomenon of the alkaline electrolyte and the effect of capturing the alkaline component by chemically reacting with the alkaline component. The polyamide amine with a low amine value has a greater effect of the former, and the polyamide amine with a high amine value has a greater effect of the latter.

[0024] The polyamide amine with a low amine value has a relatively high molecular weight and a strong polymer network formed by the polyamide. Therefore, the polyamide amine with a low amine value is less likely to deteriorate, and the physical sealing effect of suppressing the penetration of the alkaline electrolyte becomes greater.

[0025] On the other hand, the polyamide amine with a high amine value has a relatively low molecular weight and a loose polymer network, so the alkaline electrolyte is likely to penetrate. Therefore, the polyamide amine with a high amine value is likely to undergo hydrolysis by the alkaline component. The progress of hydrolysis means the capture of the alkaline component by the polyamide amine. When the polyamide is hydrolyzed by the alkaline component, its hydrophilicity increases, and the alkaline electrolyte is likely to diffuse into the sealant. Therefore, the effect of capturing the alkaline component becomes greater.

[0026] The alkaline electrolytic solution creeps upward from the inner end face facing the negative electrode of the boss portion (hereinafter also referred to as the "inner end face of the boss portion") toward the outer end face of the boss portion. The abundance of the alkaline electrolytic solution is the largest near the inner end face of the boss portion and gradually decreases from the inner end face of the boss portion toward the outer end face of the boss portion. The higher the abundance of the alkaline electrolytic solution, the more effectively the low-amine-value polyamide amine that physically suppresses the creep phenomenon of the alkaline electrolytic solution acts. The lower the abundance of the alkaline electrolytic solution, the more effectively the high-amine-value polyamide amine that chemically reacts with the alkaline component to capture the alkaline component acts. Therefore, by satisfying A1 < A2, leakage can be effectively prevented.

[0027] In a high-temperature and high-humidity environment, moisture is supplied from the gas vent holes of the negative electrode terminal plate, accelerating the creep phenomenon. Even in such a case, the amount of the alkaline electrolytic solution that permeates through the first sealant of the hole inner seal portion and reaches the outer end face of the boss portion is minute. The smaller the amount of the alkaline electrolytic solution, the more prominent the sealing effect by the second sealant containing the high-amine-value polyamide amine becomes.

[0028] The difference (A2 - A1) between the amine value A2 of the second sealant and the amine value A1 of the first sealant is preferably in the range of 40 to 150. In this case, the effect of physically suppressing the creep phenomenon of the alkaline electrolytic solution near the inner end face of the boss portion and the effect of capturing minute amounts of alkaline components at the outer end face of the boss portion become more prominent respectively. Therefore, the effect of preventing leakage becomes higher.

[0029] The amine value A1 of the first sealant may be, for example, in the range of 50 to 110, and more preferably in the range of 80 to 100. When the low-amine-value polyamide amine has an amine value within the above range, the polymer network is sufficiently strong and deterioration hardly occurs. In other words, hydrolysis of the polyamide amine hardly progresses, but the physical sealing effect of suppressing the penetration of the alkaline electrolytic solution becomes larger. If the amine value is 50 or more, the handling property as a sealant is good, and if the amine value is 110 or less, the physical sealing effect becomes significantly larger.

[0030] The amine value A2 of the second sealing agent may be, for example, in the range of 150 to 300, and more preferably in the range of 160 to 180. When the polyamide amine having a high amine value has an amine value within the above range, the polymer network is loose and the alkaline electrolyte easily penetrates. Therefore, the polyamide amine is liable to be hydrolyzed by the alkaline component, and the chemical sealing action for capturing the alkaline component becomes large. If the amine value is 150 or more, the chemical sealing action becomes significantly large, and if the amine value is 300 or less, excessive hydrolysis does not occur and the function as a sealing agent is hardly inhibited.

[0031] The creep phenomenon of the alkaline electrolyte is promoted when a part of the boss portion (particularly, the inner end face of the boss portion) is buried in the negative electrode. On the other hand, from the viewpoint of increasing the capacity of the alkaline dry battery, it is desirable to increase the volume of the negative electrode. The larger the volume of the negative electrode, the larger the volume of the boss portion buried in the negative electrode, and the creep phenomenon of the alkaline electrolyte is promoted. On the other hand, when the first sealing agent and the second sealing agent satisfying the amine value A1 < A2 are respectively arranged in the hole inner sealing portion and the outer end face of the boss portion, even when the inner end face of the boss portion is buried in the negative electrode, leakage of liquid under a high temperature and high humidity environment can be significantly suppressed.

[0032] For the material of the gasket, polyamides such as 6,6-nylon, 6,10-nylon, 6,12-nylon, etc. are used. Among them, it is preferable to use 6,10-nylon, 6,12-nylon, etc.

[0033] Next, the amine value will be described. The amine value of the polyamide is a dimensionless number represented by the number of mg of potassium hydroxide equal to the equivalent amount of perchloric acid required to neutralize all the basic nitrogen contained in 1 g of the polyamide.

[0034] The amine value is measured by the "Potentiometric titration method" of JIS K7237 (1995 4.1).

[0035] (1) Weigh a sample of polyamide corresponding to 2 to 3 mmol of basic nitrogen in a beaker up to 0.1 mg. (2) Dissolve the weighed polyamide sample in 100 mL of a mixed solvent of o-nitrotoluene and acetic acid. (3) Using a potentiometric titrator, titrate the obtained solution with 0.1 mol / L perchloric acid acetic acid solution. The inflection point of the obtained titration curve is taken as the endpoint of the titration, and the amount of 0.1 mol / L perchloric acid acetic acid solution consumed is read to the nearest 0.01 mL.

[0036] The relationship between the values ​​obtained from the potentiometric titrator and the corresponding titration volume of 0.1 mol / L perchloric acid acetic acid solution is plotted, and the inflection point obtained on the titration curve is taken as the endpoint. The total amine number is calculated from the amount of 0.1 mol / L perchloric acid acetic acid solution consumed. The formula for calculating the total amine number is shown below.

[0037] JPEG0007909194000001.jpg13163

[0038] A: Total amine value V3: Volume (mL) of 0.1 mol / L perchloric acid acetate solution consumed during titration to the endpoint. V4: Amount of 0.1 mol / L perchloric acid acetate solution consumed in the blank test (mL) f: Factor of 0.1 mol / L perchloric acid acetate solution m2: Mass of the sample (g)

[0039] Embodiments of the present invention will be further described below with reference to the drawings. However, the present invention is not limited to the embodiments described below.

[0040] Figure 1 shows a half-sectional view of an example of the internal structure of an alkaline dry cell 10 according to the present disclosure. Figure 2 shows an enlarged cross-sectional view of the main part of the same embodiment.

[0041] The cylindrical alkaline battery 10 includes a battery case 1, a positive electrode 2, a negative electrode (gel-like negative electrode) 3, a separator 4, and an alkaline electrolyte (not shown) arranged inside the battery case 1. The alkaline battery 10 has an inside-out structure.

[0042] The battery case 1 is a bottomed cylindrical case and functions as the positive electrode terminal. The battery case 1 is obtained, for example, by press-forming a nickel-plated steel sheet into a predetermined shape. A conductive coating may be formed on the inner surface of the battery case 1. The positive electrode 2 is a hollow cylindrical shape and is positioned in contact with the inner wall of the battery case 1. The negative electrode (gel-like negative electrode) 3 is positioned within the hollow portion of the positive electrode 2. The separator 4 is positioned between the positive electrode 2 and the negative electrode 3.

[0043] The separator 4 consists of a cylindrical separator 4a and a base paper 4b. The separator 4a is positioned along the inner surface of the hollow portion of the positive electrode 2, separating the positive electrode 2 from the negative electrode 3. The base paper 4b is positioned at the bottom of the hollow portion of the positive electrode 2, separating the negative electrode 3 from the battery case 1.

[0044] The opening of the battery case 1 is sealed by a sealing unit 9. The sealing unit 9 includes a gasket 5, a negative electrode current collector 6, and a negative electrode terminal plate 7 that functions as a negative electrode terminal. The negative electrode current collector 6 has a nail shape with a cylindrical body 6a and a flange (head) 6b. The negative electrode current collector 6 can be obtained, for example, by press-forming a brass wire into a nail shape of predetermined dimensions. The outer surface of the battery case 1 is covered with an outer label 8. The negative electrode terminal plate 7 can be obtained, for example, by press-forming a nickel-plated steel sheet or a tin-plated steel sheet into a predetermined shape.

[0045] As shown in Figure 2, the gasket 5 comprises a boss portion 5a, an outer peripheral portion 5b, and a connecting portion 5c that connects the boss portion 5a and the outer peripheral portion 5b. The connecting portion 5c is continuous with the boss portion 5a on the upper side of the boss portion 5a (the side furthest from the bottom of the battery case) and is continuous with the outer peripheral portion 5b on the lower side of the outer peripheral portion 5c (the side closer to the bottom of the battery case). The connecting portion 5c usually has a thin-walled portion (not shown) formed as an explosion-proof valve. The boss portion 5a has a through hole into which the body of the negative electrode current collector 6 is inserted. The outer peripheral portion 5b is interposed between the outer peripheral edge of the negative electrode terminal plate 7 and the open end of the battery case 1, and serves to seal the space between the negative electrode terminal plate 7 and the open end of the battery case 1.

[0046] The body portion 6a of the negative electrode current collector 6 is inserted into a through hole provided in the boss portion of the gasket 5 and then inserted into the negative electrode 3. The flange portion 6b of the negative electrode current collector 6 is welded at its joint surface to the central flat portion of the inner surface of the negative electrode terminal plate 7.

[0047] A first sealant 11a is interposed between the inner circumferential surface of the through hole in the boss portion 5a and the outer circumferential surface of the body portion 6a of the negative electrode current collector 6 (in-hole sealing portion). The first sealant 11a suppresses the phenomenon of the alkaline electrolyte rising up the body portion 6a of the negative electrode current collector 6.

[0048] A second sealant 11b is interposed between the end face of the negative electrode current collector 6 of the boss portion 5a facing the flange portion 6b and the back surface of the joining surface of the flange portion 6b (the outer end face of the boss portion). The second sealant 11b suppresses further diffusion of the alkaline electrolyte that has passed through the first sealant 11a and reached the outer end face of the boss portion to the outside.

[0049] Furthermore, a portion of the first sealant may reach the outer end face of the boss portion. Conversely, a portion of the second sealant may reach the area of ​​the hole sealing portion closer to the outside of the battery case. It is sufficient that the amount of the second sealant present at the outer end face of the boss portion is sufficiently greater than that of the first sealant.

[0050] The open end of the battery case 1 is crimped to the outer edge of the negative electrode terminal plate 7 via the outer periphery of the gasket 5. The outer surface of the battery case 1 is covered with an outer label 8. The battery case 1, gasket 5, and negative electrode terminal plate 7 constitute the battery housing. The positive electrode 2, negative electrode 3, separator 4, and alkaline electrolyte (not shown) are power generation elements arranged within the battery housing.

[0051] Near the flange of the negative electrode terminal plate 7, a gas vent hole 7h is provided to release gas to the outside when the explosion-proof function of the thin-walled portion of the gasket 5 is activated.

[0052] The thin-walled sections are formed, for example, in an annular or radial shape. The thin-walled sections should be configured such that when an abnormal internal pressure is reached in the battery, stress is concentrated and they rupture, allowing the internal gas to be released.

[0053] The diameter of the negative electrode current collector 6 is preferably 2.0 mm or less, and more preferably 1.8 mm or less. Furthermore, from the viewpoint of ensuring excellent current collection performance, the diameter of the negative electrode current collector 6 is preferably 1.1 mm or more, and more preferably 1.15 mm or more.

[0054] The outer diameter of the boss portion 5a is preferably, for example, 3.0 mm to 4.5 mm. The outer diameter of the outer circumference portion 5b of the gasket 5 is determined by the battery size.

[0055] The following provides a further explanation of the specific configuration of the power generation elements in alkaline batteries. 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. Examples of positive electrode active materials include manganese dioxide powder and nickel oxyhydroxide powder. Examples of conductive agents include graphite powder.

[0056] For example, the gel-like negative electrode 3 may be a mixture containing a negative electrode active material, an alkaline electrolyte, and a gelling agent. Zinc alloy powder may be used as the negative electrode active material. Polyacrylic acid or a partially sodium salt of polyacrylic acid may be used as the gelling agent. To improve the corrosion resistance of the zinc alloy, metal compounds with high hydrogen overpotential, such as indium and bismuth, or surfactants may be added to the mixture.

[0057] For example, the separator 4 may be a nonwoven fabric mainly composed of polyvinyl alcohol fibers and rayon fibers.

[0058] The positive electrode 2, the gel-like negative electrode 3, and the separator 4 each contain an alkaline electrolyte. For example, the alkaline electrolyte is an aqueous solution containing 30-40% by mass of potassium hydroxide and 1-3% by mass of zinc oxide.

[0059] The embodiments of the present invention will be further described below based on examples, but the present invention is not limited to these examples. Here, an AAA (LR03) alkaline battery with the structure shown in Figure 1 was fabricated.

[0060] Examples 1-3, Comparative Examples 1-3 (1) Fabrication of the sealing unit A gasket was manufactured by injection molding 6,12-nylon into a predetermined shape using a mold.

[0061] A negative electrode current collector was fabricated by processing brass with a copper content of 65% by mass into a nail shape with a total length of 30 mm and a body diameter of 1.20 mm. A negative electrode terminal plate was fabricated by press-forming a 0.4 mm thick nickel-plated steel sheet into a predetermined shape, and the flange portion of the negative electrode current collector was welded to the negative electrode terminal plate.

[0062] A polyamide having an amine value of A1, as shown in Table 1, was applied as a first sealant to the outer circumferential surface of the negative electrode current collector body, specifically to the portion intended to contact the inner circumferential surface of the through-hole in the boss portion of the gasket. Next, a polyamide having an amine value of A2, as shown in Table 1, was applied as a second sealant to the back surface of the joint surface of the flange portion of the negative electrode current collector (the portion intended to contact the outer end surface of the boss portion). After that, the negative electrode current collector was press-fitted into the through-hole in the boss portion of the gasket to assemble the sealing unit.

[0063] (2) Preparation of the positive electrode Electrolytic manganese dioxide powder with an average particle size of 35 μm and graphite powder with an average particle size of 15 μm were mixed in a mass ratio of 94:6. 2 parts by mass of alkaline electrolyte were added to 100 parts by mass of the mixture, and after thorough stirring, the mixture was compressed to obtain a flake-shaped positive electrode mixture. The flake-shaped positive electrode mixture was pulverized into granules, then pressure-molded into hollow cylindrical pellets, and the resulting molded body was designated as positive electrode 2.

[0064] The alkaline electrolyte used was an aqueous solution containing 33% by mass of potassium hydroxide and 2% by mass of zinc oxide.

[0065] (3) Preparation of the negative electrode A gelling agent (a mixture of polyacrylic acid and partially sodium salt powder of polyacrylic acid), an alkaline electrolyte, and zinc alloy powder with an average particle size of 110 μm were mixed in a mass ratio of 0.8:34.2:65.0 to obtain a gel-like negative electrode 3.

[0066] (4) Battery assembly The positive electrode 2 was inserted into the battery case 1, and a pressure jig was used to press the positive electrode 2 tightly against the inner wall of the battery case 1. A bottomed cylindrical separator 4 was placed in the hollow of the positive electrode 2. The separator 4 was made of a nonwoven fabric mainly composed of polyvinyl alcohol fibers and rayon fibers. After injecting alkaline electrolyte into the separator 4 and elapsed for a predetermined time, the gel-like negative electrode 3 was filled into the separator 4. The outer circumference of the gasket of the sealing unit was placed near the opening of the battery case 1, and the opening end of the battery case 1 was folded inward to seal it, completing the battery. The amount of gel-like negative electrode was adjusted so that the inner end surface of the boss portion did not come into contact with the gel-like negative electrode. Twenty alkaline dry cell batteries were made for each example. Batteries A1 to A3 are from Examples 1 to 3, and batteries B1 to B3 are from Comparative Examples 1 to 3.

[0067] (5) Evaluation (5-1) Twenty alkaline dry cell batteries from each example were stored for 100 days (equivalent to 10 years at room temperature) under conditions of 60°C and 90% RH, and the number of leaks due to creep (leakage rate out of 20 batteries) was investigated. The results are shown in Table 1.

[0068] (5-2) Twenty alkaline dry cell batteries from each example were stored for 200 days (equivalent to 20 years at room temperature) under conditions of 60°C and 90% RH, and the number of leaks due to creep (leakage rate out of 20 batteries) was investigated. The results are shown in Table 2.

[0069] The presence or absence of leakage was confirmed by soaking a pulp sheet with a test solution of indicator (cresol red):ethanol:distilled water = 1g:500mL:500mL and bringing it into contact with the outer surface of the negative electrode terminal plate of the battery. When the color of the pulp sheet changed from yellow to red, it was determined that leakage had occurred because the pH of the outer surface of the negative electrode terminal plate had become alkaline.

[0070]

Table 1

[0071]

Table 2

[0072] 《Examples 4 to 6, Comparative Examples 4 to 6》 Alkaline dry batteries were produced and evaluated in the same manner as in Examples 1 to 3 and Comparative Examples 1 to 3, except that the amount of the gel-like negative electrode was increased by 10% so that the inner end surface of the boss portion was buried in the gel-like negative electrode. For each example, 20 alkaline dry batteries were produced respectively. Batteries A4 to A6 are the batteries of Examples 4 to 6, and batteries B4 to B6 are the batteries of Comparative Examples 4 to 6.

[0073]

Table 3

[0074]

Table 4

[0075] From Table 1, it can be seen that from the viewpoint of ensuring the recommended service life equivalent to 10 years at room temperature, which was the conventional required characteristic, it is not required that the amine value satisfies A1 < A2, and even if A1 = A2, the required characteristics can be sufficiently satisfied.

[0076] On the other hand, from Table 2, it can be understood that from the viewpoint of ensuring a longer recommended service life (equivalent to 20 years at room temperature), it is effective that the amine value satisfies A1 < A2.

[0077] From the comparison of Tables 3 and 4, it can be understood that even under the conditions where the inner end surface of the boss portion is buried in the gel-like negative electrode and the creep phenomenon is promoted, when the amine value satisfies A1 < A2, leakage can be effectively prevented.

Industrial Applicability

[0078] The alkaline dry cell battery described herein is useful as a power source for various electronic devices because it can suppress leakage over a long period of time. [Explanation of Symbols]

[0079] 1: Battery case, 2: Positive electrode, 3: Gel-type negative electrode, 4: Separator, 5: Gasket, 5a: Boss part, 5b: Outer circumference part, 5c: Connecting part, 6: Negative electrode current collector, 6a: Body part, 6b: Flange part, 7: Negative electrode terminal plate, 7h: Gas vent hole, 8: Outer label, 9: Sealing unit, 10: Alkaline dry cell, 11a: First sealant, 11b: Second sealant

Claims

1. A battery case having an opening, The power generation element housed in the aforementioned battery case, A sealing unit for sealing the aforementioned opening, Equipped with, The power generation element comprises a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode. The sealing unit comprises a negative electrode terminal plate, a nail-shaped negative electrode current collector, and a gasket. The negative electrode current collector comprises a flange portion having a bonding surface joined to the negative electrode terminal plate, and a columnar body portion. The gasket comprises a boss portion having a through hole that penetrates the body portion, an outer peripheral portion that contacts the open end of the battery case, and a connecting portion that connects the boss portion and the outer peripheral portion. A first sealant is interposed between the inner circumferential surface of the through hole in the boss portion and the outer circumferential surface of the body portion of the negative electrode current collector. A second sealant is interposed between the end face of the boss portion facing the flange portion and the back surface of the joining surface of the flange portion. The first and second encapsulants are polyamides. The amine values ​​A1 of the first encapsulant and A2 of the second encapsulant satisfy A1 < A2. An alkaline dry cell in which the difference between the amine value A2 of the second encapsulant and the amine value A1 of the first encapsulant is in the range of 40 to 250.

2. The amine value A1 of the first sealing agent is in the range of 50 to 110. The alkaline dry cell according to claim 1, wherein the amine value A2 of the second encapsulant is in the range of 150 to 300.

3. The amine value A1 of the first sealing agent is in the range of 80 to 100. The alkaline dry cell according to claim 1, wherein the amine value A2 of the second encapsulant is in the range of 160 to 180.

4. The alkaline dry cell according to any one of claims 1 to 3, wherein a portion of the boss portion is embedded in the negative electrode.

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