Alkaline battery

Abstract

The present disclosure provides an alkaline battery capable of suppressing the leakage of an alkaline electrolyte. This alkaline battery comprises a battery case (1) having an opening, a power generation element accommodated in the battery case (1), and a sealing unit (9) for sealing the opening, wherein: the power generation element includes a positive electrode (2), a negative electrode (3), and a separator (4) interposed between the positive electrode (2) and the negative electrode (3); the sealing unit (9) includes a negative electrode terminal plate (7), a negative electrode current collector (6) joined to the negative electrode terminal plate (7), and a gasket (5); the negative electrode current collector (6) has a columnar body part (6a), and a head part (6b) which protrudes in a radially outward direction from one end portion of the columnar body part (6a) in the longitudinal direction; the gasket (5) is formed of a polypropylene resin and includes a boss part having a through-hole through which the body part (6a) passes, an outer peripheral part which is in contact with an opening end portion of the battery case (1), and a connection part which connects the boss part and the outer peripheral part; the head part (6b) of the negative electrode current collector (6) is disposed on one end side of the boss part in the longitudinal direction; and the elastic modulus, measured at the central section on the outer peripheral surface of the boss part in a state in which the body part (6a) passes through the through-hole, is 1.50-2.50 GPa.

Description

alkaline batteries

[0001] The present invention relates to an alkaline dry battery, and more particularly to an alkaline dry battery having a gasket made of polypropylene resin.

[0002] Alkaline batteries (alkaline manganese batteries) are widely used because they have a larger battery capacity and can extract a larger current than manganese batteries. Alkaline batteries typically include a positive electrode, a negative electrode, a separator interposed between the positive and negative electrodes, and an alkaline electrolyte. The positive electrode contains manganese dioxide as a positive electrode active material. Various studies have been conducted to improve the performance of alkaline batteries.

[0003] For example, Patent Document 1 listed below describes an alkaline dry battery having a main body formed by inserting a cylindrical positive electrode mixture into a positive electrode can and filling the hollow portion of the positive electrode mixture with a negative electrode having zinc as the negative electrode active material via a separator, and a sealing body formed by inserting a metal current collector into a current collector insertion hole formed in a boss portion of a gasket made of thermoplastic resin (e.g., polypropylene).

[0004] Patent Document 1 below describes forming the inner diameter of the current collector insertion hole formed in the boss portion of the gasket slightly smaller than the diameter (outer diameter) of the current collector, specifically, setting the inner diameter of the current collector insertion hole to 1.3 mm when the diameter (outer diameter) of the current collector is 1.5 mm. Patent Document 1 also describes that by adopting the above configuration, it is possible to improve adhesion between the boss portion of the gasket and the current collector, thereby preventing creep in gaskets made of thermoplastic resins such as polypropylene and suppressing leakage of alkaline electrolyte.

[0005] Patent No. 3067320

[0006] As described above, in alkaline batteries equipped with gaskets made of thermoplastic resins such as polypropylene, studies have been conducted to suppress leakage of alkaline electrolyte by focusing on the relationship between the inner diameter of the current collector insertion hole formed in the boss portion of the gasket and the diameter (outer diameter) of the current collector. However, it is difficult to say that sufficient studies have been conducted yet that focus on other factors.

[0007] Therefore, an object of the present disclosure is to provide an alkaline dry battery that can suppress leakage of alkaline electrolyte.

[0008] One aspect of the present invention provides a battery case including an opening, a power generating element housed in the battery case, and a sealing unit that seals the opening, wherein the power generating element includes a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode, and the sealing unit includes a negative electrode terminal plate, a negative electrode current collector joined to the negative electrode terminal plate, and a gasket, and the negative electrode current collector has a cylindrical body portion and a head portion that protrudes radially outward from one end of the cylindrical body portion in a longitudinal direction, and The gasket includes a boss portion having a through hole that passes through the body portion, an outer periphery that contacts the open end of the battery case, and a connecting portion that connects the boss portion and the outer periphery, and is made of polypropylene resin; the head of the negative electrode current collector is disposed on one end side of the boss portion in the longitudinal direction; and the elastic modulus G measured at the center of the outer periphery of the boss portion when the body portion is passed through the through hole is 1.50 GPa or more and 2.50 GPa or less.

[0009] According to the present disclosure, an alkaline dry battery capable of suppressing leakage of alkaline electrolyte can be provided.

[0010] Fig. 2 is a diagram showing an example of a test force-depth curve. Fig. 3 is a half-sectional view showing an example of the internal structure of an alkaline dry battery according to an embodiment of the present disclosure. Fig. 4 is an enlarged cross-sectional view of a main part of Fig. 2. Fig. 5 is a cross-sectional view for explaining the taper angle on the outer peripheral surface of the boss portion.

[0011] Below, embodiments of the present disclosure will be described using examples, but the present disclosure is not limited to the examples described below. In the following description, specific numerical values ​​and materials may be exemplified, but other numerical values, materials, etc. may be applied as long as the effects of the present disclosure are obtained. Note that known components may be applied to components characteristic of the present disclosure. In this specification, when a "range from numerical value A to numerical value B" is mentioned, the range includes numerical value A and numerical value B.

[0012] In the following description, when lower and upper limits of numerical values ​​relating to specific physical properties, conditions, etc. are exemplified, any of the exemplified lower limits and any of the exemplified upper limits can be arbitrarily combined, as long as the lower limit is not equal to or greater than the upper limit. When multiple materials are exemplified, one of them can be selected and used alone, or two or more can be used in combination, unless otherwise specified.

[0013] The present disclosure encompasses any combination of two or more features arbitrarily selected from the appended claims, i.e., any combination of two or more features arbitrarily selected from the appended claims can be combined unless a technical contradiction arises.

[0014] [Alkaline Battery] The type of alkaline battery according to the embodiment of the present disclosure is not particularly limited. The alkaline battery may be, for example, any of D to AAA sizes, or other sizes.

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

[0016] The sealing unit includes a negative electrode terminal plate, a negative electrode current collector, and a gasket. The negative electrode terminal plate functions to close the opening of the battery case and also functions as a negative electrode terminal. The negative electrode terminal plate usually has a gas vent hole for releasing gas to the outside when the internal pressure of the battery rises significantly. The negative electrode current collector has a cylindrical body and a head that protrudes radially outward from one end of the cylindrical body in the longitudinal direction. The negative electrode current collector has a cylindrical body and a head, and is preferably nail-shaped. The head has a joining surface that is joined to the negative electrode terminal plate.

[0017] The gasket includes a boss portion having a through hole that penetrates the body portion of the negative electrode current collector, an outer peripheral portion interposed between the peripheral edge of the negative electrode terminal plate and the open end of the battery case, and a connecting portion that connects the boss portion and the outer peripheral portion. The boss portion is cylindrical, and a through hole is formed so as to penetrate the cylindrical portion in the longitudinal direction. The head of the negative electrode current collector is located at one end of the boss portion in the longitudinal direction. The connecting portion may have a thin-walled portion that has an explosion-proof function. The thin-walled portion ruptures when the internal pressure of the battery rises significantly or more. In such a case, gas is released to the outside of the battery through a gas vent hole provided in the negative electrode terminal plate.

[0018] The gasket is made of a polypropylene resin. The polypropylene resin is, for example, a resin composed of 95% by mass or more and 100% by mass or less of polypropylene. The polypropylene resin may contain a resin component other than polypropylene, or may contain an additive such as an antioxidant. The polypropylene resin may contain an isotactic structure, a syndiotactic structure, or an atactic structure as a propylene-derived structural unit portion. From the viewpoint of industrial availability, the polypropylene resin preferably contains an isotactic structure as a main propylene-derived structural unit portion.

[0019] In the alkaline dry battery according to the embodiment of the present disclosure, it is important that the elastic modulus G measured at the center of the outer circumferential surface of the boss portion when the body portion of the negative electrode current collector is inserted through the through-hole of the boss portion is 1.50 GPa or more and 2.50 GPa or less. The reason for this is explained below.

[0020] When the body of the negative electrode current collector penetrates the boss, a pressing force is applied from the inside (inner peripheral surface) to the outside (outer peripheral surface) by the body of the negative electrode current collector. Therefore, on the inner side where a large pressing force is applied, the boss loses its elastic properties and exhibits plastic properties. On the other hand, on the outer side where the applied pressing force is small, the boss does not lose its elastic properties and continues to exhibit elastic properties. That is, in such a boss, a plastic region exhibiting plastic properties exists on the inner side, and an elastic region exhibiting elastic properties exists on the outer side. When deformation occurs in the boss due to such pressing force, the residual stress remaining in the plastic region decreases, and the residual stress remaining in the elastic region increases. Here, if the residual stress remaining in the boss is too large, environmental stress cracking is likely to occur in the boss due to the interaction between the large residual stress and the alkaline electrolyte when an alkaline battery is stored at high temperatures with the boss in contact with the alkaline electrolyte (e.g., when stored in an environment at a temperature of 80°C for three months). On the other hand, if the residual stress remaining in the boss becomes too small, the boss will lose its toughness and become brittle, which may lead to cracks in the boss.

[0021] In alkaline batteries according to embodiments of the present disclosure, the elastic modulus G measured at the center of the outer peripheral surface of the boss portion falls within the above-described range, allowing the boss portion to have a primarily plastic region while also having a moderate elastic region. This makes it possible to prevent environmental stress cracking in the boss portion during high-temperature storage in contact with alkaline electrolyte in alkaline batteries according to embodiments of the present disclosure. Furthermore, it is possible to prevent cracks in the boss portion due to brittleness. This also makes it possible to prevent leakage of alkaline electrolyte in alkaline batteries according to embodiments of the present disclosure.

[0022] As described above, the boss portion is a cylindrical body. The central portion of the outer peripheral surface of the boss portion refers to the central portion in the length direction of the outer peripheral surface of this cylindrical boss portion, and more specifically, refers to a range of 0.5L±0.05L, where L is the length of the portion of the inner peripheral portion of the boss that contacts the negative electrode current collector. The elastic modulus G can be determined by arithmetically averaging the elastic modulus values ​​measured at any 10 points along the outer peripheral surface within the above range.

[0023] The elastic modulus G can be adjusted by adjusting the ratio between the inner diameter of the boss portion and the outer diameter of the body portion of the negative electrode current collector, or by adjusting the ratio between the inner diameter and outer diameter of the boss portion and the outer diameter of the body portion of the negative electrode current collector. Specifically, the value of the elastic modulus G can be increased by increasing the ratio of the outer diameter of the body portion of the negative electrode current collector to the inner diameter of the boss portion, and the value of the elastic modulus G can be decreased by decreasing the ratio of the outer diameter of the body portion of the negative electrode current collector to the inner diameter of the boss portion. Furthermore, the value of the elastic modulus G can be increased by increasing the ratio of the outer diameter of the boss portion to the inner diameter of the boss portion, and the value of the elastic modulus G can be decreased by decreasing the ratio of the outer diameter of the boss portion to the inner diameter of the boss portion.

[0024] The elastic modulus G can also be adjusted by making the outer diameter of the body of the negative electrode current collector larger than the inner diameter of the boss portion, and then annealing the boss portion with the body of the negative electrode current collector penetrating the through-hole of the boss portion. Specifically, the value of the elastic modulus G can be reduced by increasing the annealing temperature, and the value of the elastic modulus G can be increased by decreasing the annealing temperature. Annealing is a method of using heat to change the crystallinity of the polypropylene resin forming the boss portion and adjust the ratio of plastic regions to elastic regions in the boss portion. Furthermore, when a gasket with a boss portion is manufactured by injection molding, the crystallinity of the polypropylene resin can also be changed by appropriately adjusting conditions such as the dwell pressure, resin temperature, and mold temperature during injection molding.

[0025] The elastic modulus G can be determined by conducting a load-unload test (test conditions on the device: MODE 2) at a set test force P (mN) using a dynamic ultra-microhardness tester (manufactured by Shimadzu Corporation, model number "DUH (registered trademark)-211S") as the measuring device and a triangular pyramidal indenter (edge ​​angle 115°). The load-unload test can be conducted, for example, according to the following procedure. (1) After contacting the triangular pyramidal indenter with the measurement object (the center of the outer peripheral surface of the boss portion), the indenter is pressed into the measurement object at a constant loading rate (0.9754 mN / sec). (2) After the test force reaches the set test force P (maximum test force Pmax), the indenter is held pressed into the measurement object for 10 seconds. (3) After holding for 10 seconds, the indenter is pulled out from the measurement object at a constant unloading rate (the same rate as the loading rate).

[0026] After performing the load-unload test as described above and obtaining a test force-depth curve as shown in Figure 1, the elastic modulus G can be calculated from this test force-depth curve using the following formulas (1) to (5). The elastic modulus G calculated in this manner is also referred to as the elastic modulus by the nanoindentation method.

[0027]

[0028] where E is the Young's modulus of the object to be measured, V is the Poisson's ratio of the object to be measured, Er is the effective Young's modulus of the system (composite Young's modulus of the object to be measured and the indenter), and Ei is the Young's modulus of the indenter (diamond) (1.16 × 10 ２ gf / μm ２ ), Vi is the Poisson's ratio of the indenter (diamond) (0.07), S (= dp / dh) is the slope at the start of unloading (see Figure 1), A is the contact projected area (elastic contact area) between the indenter and the measurement object, hmax is the maximum indentation depth, and hr is the intercept where the approximation line at the start of unloading intersects with the depth axis.

[0029] In the alkaline dry battery according to the embodiment of the present disclosure, the elastic modulus G may be 2.00 GPa or more. Furthermore, the elastic modulus G may be 2.45 GPa or less, 2.40 GPa or less, or 2.35 GPa or less. When the elastic modulus G is within the above-described range, the alkaline dry battery according to the embodiment of the present disclosure is able to further suppress leakage of alkaline electrolyte.

[0030] Next, a specific configuration of an alkaline dry battery according to an embodiment of the present disclosure will be described with reference to the drawings. Fig. 2 is a half cross-sectional view showing an example of the internal structure of an alkaline dry battery according to an embodiment of the present disclosure, and Fig. 3 is an enlarged cross-sectional view of a main part of Fig. 2. Furthermore, Fig. 4 is a cross-sectional view illustrating the taper angle of the outer peripheral surface of the boss portion.

[0031] The alkaline dry battery 10 has a cylindrical shape and includes a battery case 1, a positive electrode 2 disposed in the battery case 1, a negative electrode (gelled negative electrode) 3, a separator 4, and an alkaline electrolyte (not shown). The alkaline dry battery 10 has an inside-out structure.

[0032] The battery case 1 is a cylindrical case with a bottom and functions as a positive electrode terminal. As described above, the battery case 1 has a cylindrical portion C and a bottom portion B. The battery case 1 is obtained, for example, by press-molding 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 has a hollow cylindrical shape and is arranged so as to contact the inner wall of the battery case 1. Specifically, the positive electrode 2 is arranged so that a portion of the outer circumferential surface of the cylinder contacts the inner wall of the battery case 1. The negative electrode (gelled negative electrode) 3 is arranged in the hollow portion of the positive electrode 2. The separator 4 is arranged between the positive electrode 2 and the negative electrode 3.

[0033] The separator 4 is composed of a cylindrical separator 4a and a bottom paper 4b. The separator 4a is disposed along the inner peripheral surface of the hollow portion of the positive electrode 2, separating the positive electrode 2 from the negative electrode 3. The bottom paper 4b is disposed at the bottom of the hollow portion of the positive electrode 2, separating the negative electrode 3 from the battery case 1.

[0034] 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 portion 6a and a head portion 6b. The head portion 6b has a joining surface BS that is joined to the negative electrode terminal plate 7. The negative electrode current collector 6 can be obtained, for example, by pressing a brass wire into a nail shape of predetermined dimensions. The outer peripheral surface of the battery case 1 is covered with an exterior label 8. The negative electrode terminal plate 7 can be obtained, for example, by pressing a nickel-plated steel sheet or a tin-plated steel sheet into a predetermined shape. In the alkaline dry battery according to the embodiment of the present disclosure, as shown in FIGS. 2 and 3 , the negative electrode terminal plate 7 has a flat portion 7f extending in a direction perpendicular to the extension direction of the body portion 6a and a bent portion 7b that bends and extends from the peripheral edge of the flat portion 7f toward the inside of the battery case 1. The bent portion 7b of the negative electrode terminal plate 7 also functions as a flange. Therefore, hereinafter, the bent portion 7b of the negative electrode terminal plate 7 may be referred to as a flange.

[0035] As shown in FIG. 3 , the gasket 5 includes a boss portion 5a, an outer peripheral portion 5b, and a connecting portion 5c connecting the boss portion 5a and the outer peripheral portion 5b. The connecting portion 5c is continuous with the boss portion 5a above the boss portion 5a (the side farther from the bottom B of the battery case 1) and is continuous with the outer peripheral portion 5b below the outer peripheral portion 5b (the side closer to the bottom B of the battery case 1). The connecting portion 5c typically has a thin-walled portion (not shown) formed as an explosion-proof valve. The boss portion 5a is cylindrical, and a through-hole is formed through the cylindrical body in the longitudinal direction. The body portion 6a of the negative electrode current collector 6 passes through the through-hole of the boss portion 5a. The head portion 6b of the negative electrode current collector 6 is located at one end of the boss portion 5a in the longitudinal direction. The outer peripheral portion 5 b 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 gap between the negative electrode terminal plate 7 and the open end of the battery case 1 .

[0036] In the alkaline dry battery 10, the boss portion 5a preferably has a tapered shape that tapers from one end to the other end in the longitudinal direction (see FIG. 4 ). In the alkaline dry battery 10, the taper angle θ of the outer peripheral surface of the boss portion 5a is preferably 1° or greater and 5° or less. The lower limit of the taper angle θ may be 2°. The upper limit of the taper angle θ may be 4°. The body portion 6a of the negative electrode current collector 6 is penetrated from one end to the other end in the longitudinal direction of the boss portion 5a. During this penetration, a pressure gradient is generated from one end to the other end of the boss portion 5a. However, by providing the outer peripheral surface with a taper angle θ within the above range so as to follow this pressure gradient, excessive residual stress can be further suppressed from remaining in the boss portion 5a after the body portion 6a of the negative electrode current collector 6 is penetrated through the through hole in the boss portion 5a. This further suppresses leakage of alkaline electrolyte in the alkaline dry battery 10. A boss portion having a taper angle θ of the outer peripheral surface within the above range can be obtained, for example, by adjusting the angle of the portion corresponding to the outer peripheral surface in the molding die for the boss portion.

[0037] The body 6a of the negative electrode current collector 6 passes through a through-hole formed in the boss portion 5a of the gasket 5 and is inserted into the negative electrode 3. The head 6b of the negative electrode current collector 6 is welded to the inner surface of the flat portion 7f of the negative electrode terminal plate 7 at its joint surface BS.

[0038] A sealant may be interposed between the inner circumferential surface of the through-hole of the boss portion 5a and the outer circumferential surface of the body portion 6a of the negative electrode current collector 6 (intra-hole sealing portion). The presence of the sealant can prevent the alkaline electrolyte from creeping up the body portion 6a of the negative electrode current collector 6. For example, a sealant containing polyamide can be used. Polyamide is a general term for resins or polymers having a polyamide structure. The polyamide structure has a repeating amide bond structure.

[0039] The open end of the battery case 1 is crimped to the outer peripheral end (end of the bent portion 7b) of the negative electrode terminal plate 7 via the outer peripheral portion 5b of the gasket 5. The outer surface of the battery case 1 is covered with an exterior label 8. The battery case 1, gasket 5, and negative electrode terminal plate 7 constitute a battery housing. The positive electrode 2, negative electrode 3, separator 4, and alkaline electrolyte (not shown) are power-generating elements disposed within the battery housing.

[0040] A gas vent 7h is provided near the flange (bent portion) of the negative electrode terminal plate 7 to allow gas to escape to the outside of the battery case 1 when the explosion-proof function provided by the thin portion of the gasket 5 is activated.

[0041] The thin-walled portion may be formed, for example, in a ring shape or a radial shape, and may be configured so that when an abnormal internal battery pressure is reached, stress is concentrated on the thin-walled portion, causing the thin-walled portion to break and allow the internal gas to be discharged.

[0042] The outer diameter (trunk diameter) D1 of the trunk portion of the negative electrode current collector 6 may be, for example, 2.00 mm or less, 1.80 mm or less, or 1.50 mm or less. From the viewpoint of ensuring excellent current collecting properties, the outer diameter (trunk diameter) D1 of the negative electrode current collector 6 is preferably 1.00 mm or more, more preferably 1.10 mm or more, and still more preferably 1.15 mm or more.

[0043] The inner diameter D2 of the boss portion 5a may be 0.80 mm or more, 0.85 mm or more, or 0.90 mm or more. The inner diameter D2 may be 1.50 mm or less, 1.20 mm or less, 1.15 mm or less, or 1.10 mm or less.

[0044] The outer diameter D3 of the boss portion 5a may be 3.00 mm or more, 3.40 mm or more, or 3.60 mm or more. The outer diameter D3 may be 10.00 mm or less, 4.00 mm or less, or 3.80 mm or less.

[0045] The ratio of the outer diameter (trunk diameter) D1 of the trunk portion of the negative electrode current collector 6 to the inner diameter D2 of the boss portion 5a (D1 / D2 × 100; hereinafter simply referred to as the D1 / D2 ratio) may be greater than 100%. The D1 / D2 ratio may be 105% or greater, 110% or greater, or 120% or greater. The D1 / D2 ratio may be 135% or less, or 130% or less. When the D1 / D2 ratio is in the above-mentioned numerical range, it becomes easier to adjust the elastic modulus measured at the center of the outer peripheral surface of the boss portion 5a to a range of 1.50 GPa or greater and 2.50 GPa or less.

[0046] The ratio of the outer diameter D3 of the boss portion 5a to the inner diameter D2 of the boss portion 5a (D3 / D2 × 100; hereinafter simply referred to as the D3 / D2 ratio) may be 200% or more, 250% or more, or 300% or more. The D3 / D2 ratio may be 500% or less, 450% or less, 400% or less, 350% or less, or 330% or less. When the D3 / D2 ratio is in the above-mentioned numerical range, it becomes easy to adjust the elastic modulus measured at the center of the outer peripheral surface of the boss portion 5a to a range of 1.50 GPa or more and 2.50 GPa or less.

[0047] The outer diameter of the outer peripheral portion 5b of the gasket 5 is determined by the battery size.

[0048] The specific configuration of the power generating element of the alkaline dry battery will be further described below.

[0049] (Positive Electrode) The positive electrode 2 contains manganese dioxide as a positive electrode active material. The positive electrode 2 usually contains a positive electrode active material and a conductive agent, and further contains a binder as needed. The positive electrode 2 may be formed by pressure molding a positive electrode mixture into a cylindrical shape. A positive electrode molded into a cylindrical shape, including a cylindrical shape, is also called a positive electrode pellet. The positive electrode mixture contains, for example, a positive electrode active material, a conductive agent, and an alkaline electrolyte, and further contains a binder as needed. After being housed in the battery case 1, the cylindrical positive electrode 2 may be pressed so as to adhere to the inner wall of the battery case 1.

[0050] A preferred example of manganese dioxide as a positive electrode active material is electrolytic manganese dioxide. Alternatively, natural manganese dioxide or chemical manganese dioxide may be used. The crystal structure of manganese dioxide includes α-type, β-type, γ-type, δ-type, ε-type, η-type, λ-type, and ramsdellite-type.

[0051] The manganese dioxide powder may have an average particle size (D50) of, for example, 25 μm or more and 60 μm or less, in order to easily ensure the filling property of the positive electrode and the diffusibility of the electrolyte solution in the positive electrode. The average particle size (D50) is the median size at which the cumulative value in the volume-based particle size distribution is 50%. The median size can be determined, for example, using a laser diffraction / scattering particle size distribution analyzer.

[0052] From the viewpoint of moldability and suppression of expansion of the positive electrode, the BET specific surface area of ​​manganese dioxide is, for example, 20 m ２ / g or more 50m ２ The BET specific surface area can be measured, for example, using a specific surface area measuring device based on a nitrogen adsorption method.

[0053] The conductive agent may be a conductive carbon material. Examples of conductive carbon materials include carbon black (acetylene black) and graphite. Examples of graphite include natural graphite and artificial graphite. A powdered conductive agent may be used. The average particle diameter (D50) of the conductive agent may be in the range of 3 μm to 20 μm. The content of the conductive agent in the positive electrode may be in the range of 3 parts by mass to 10 parts by mass, or in the range of 5 parts by mass to 9 parts by mass, relative to 100 parts by mass of manganese dioxide.

[0054] A silver compound may be added to the positive electrode to absorb hydrogen generated inside the battery. Examples of silver compounds include silver oxide (Ag ２ O, AgO, Ag ２ O ３ etc.), silver-nickel composite oxide (AgNiO ２ ) etc.

[0055] (Negative Electrode) The negative electrode 3 contains zinc alloy powder as the negative electrode active material. From the viewpoint of corrosion resistance, the zinc alloy may contain at least one selected from the group consisting of indium, bismuth, and aluminum. The indium content in the zinc alloy may be in the range of 0.01% by mass to 0.1% by mass. The bismuth content in the zinc alloy may be in the range of 0.003% by mass to 0.02% by mass. The aluminum content in the zinc alloy may be in the range of 0.001% by mass to 0.03% by mass. From the viewpoint of corrosion resistance, the content of elements other than zinc in the zinc alloy may be in the range of 0.025% by mass to 0.08% by mass.

[0056] The average particle size (D50) of the zinc alloy powder may be in the range of 100 μm to 200 μm, or in the range of 110 μm to 160 μm, from the viewpoints of the filling property of the negative electrode and the diffusibility of the electrolyte in the negative electrode. The average particle size (D50) is as described above.

[0057] The negative electrode 3 may contain a gelling agent, a surfactant, and an electrolyte solution in addition to the zinc alloy powder. The negative electrode 3 may be formed from a mixture of the zinc alloy powder, the gelling agent, the surfactant, and the electrolyte solution. A negative electrode 3 containing a gelling agent is also called a gelled negative electrode. When the negative electrode is formed from the mixture, it is preferable to add the additives, such as the gelling agent and the surfactant, to the electrolyte solution used to prepare the negative electrode in advance, in order to more uniformly disperse the additives in the negative electrode 3. The alkaline electrolyte solution described below can be used as the electrolyte. To improve corrosion resistance, the negative electrode 3 may be appropriately added with a compound containing a metal with a high hydrogen overvoltage, such as indium or bismuth.

[0058] Examples of gelling agents include cross-linked polyacrylic acid and partial sodium salts of cross-linked polyacrylic acid. When the gelling agent contains both cross-linked polyacrylic acid and partial sodium salts of cross-linked polyacrylic acid, the mass ratio thereof may be cross-linked polyacrylic acid: partial sodium salt of cross-linked polyacrylic acid=1:0.5-4, or cross-linked polyacrylic acid: partial sodium salt of cross-linked polyacrylic acid=1:1-3.

[0059] The surfactants include those containing an ethylene oxide group (-CH ２ -CH ２ Anionic surfactants having a (-O-) bond (hereinafter referred to as anionic surfactant A) may include a polyoxyethylene chain (plurality of ethylene oxide groups bonded in a linear chain), a hydrophobic group bonded to one end (e.g., an oxygen atom) of the polyoxyethylene chain, and an anionic group bonded to the other end (e.g., a carbon atom) of the polyoxyethylene chain. The n ethylene oxide groups bonded in a linear chain may be (-CH ２ -CH ２ -O-) ｎ It is expressed as:

[0060] The number of ethylene oxide groups bonded in a linear chain may be 3 or more, or 4 or more. The number of ethylene oxide groups may be 6 or less, or 5 or less. The number of carbon atoms in the hydrophobic group may be 4 or more, 7 or more, 10 or more, or 12 or more. The number of carbon atoms in the hydrophobic group may be 20 or less, 18 or less, or 15 or less. The hydrophobic group may be a hydrocarbon group (e.g., an alkyl group). The hydrophobic group may be a hydrocarbon group having 4 to 15 carbon atoms, a hydrocarbon group having 10 to 15 carbon atoms, or a hydrocarbon group having 12 to 15 carbon atoms. The hydrocarbon group may also be a linear alkyl group. Examples of anionic groups include a phosphate group and a carboxyl group.

[0061] (Negative electrode current collector) The material of the negative electrode current collector 6 may be a metal (simple metal or alloy). Examples of the metal include a metal containing copper. The copper-containing metal may be copper alone or an alloy containing copper (copper-based alloy). Examples of the copper-based alloy include an alloy containing copper and zinc (e.g., brass). The negative electrode current collector 6 may be plated with tin or the like, as necessary.

[0062] The separator 4 may be made of a nonwoven fabric mainly composed of fibers, a microporous resin film, or the like. Examples of fiber materials include cellulose and polyvinyl alcohol. The nonwoven fabric may be made of a blend of cellulose fibers and polyvinyl alcohol fibers, or a blend of rayon fibers and polyvinyl alcohol fibers. Examples of microporous film materials include resins such as cellophane and polyolefin. The thickness of the separator 4 may be in the range of 200 μm to 300 μm.

[0063] (Alkaline Electrolyte) As the alkaline electrolyte, for example, an alkaline solution containing potassium hydroxide is used. The potassium hydroxide concentration in the alkaline electrolyte is preferably in the range of 30% by mass to 50% by mass, and more preferably in the range of 30% by mass to 40% by mass. The alkaline electrolyte may contain lithium hydroxide (LiOH), sodium hydroxide (NaOH), cesium hydroxide (CsOH), rubidium hydroxide (RbOH), or the like. The positive electrode 2, the negative electrode 3, and the separator 4 each contain an alkaline electrolyte.

[0064] The alkaline electrolyte may contain a surfactant. By including a surfactant, the dispersibility of the negative electrode active material can be improved. As the surfactant, those described for the negative electrode 3 can be used. The content of the surfactant in the alkaline electrolyte may be in the range of 0% by mass to 0.5% by mass, or in the range of 0% by mass to 0.2% by mass.

[0065] (Battery Housing) As described above, the battery housing is composed of the battery case 1, the gasket 5, and the negative electrode terminal plate 7. The battery case 1 may be, for example, a cylindrical metal case with a bottom. The metal case may be, for example, a nickel-plated steel plate. In order to reduce the contact resistance between the battery case 1 and the positive electrode 2, the inner circumferential surface of the battery case 1 may be coated with a carbon coating. The negative electrode terminal plate 7 may be formed from the same material as the metal case (for example, a nickel-plated steel plate).

[0066] [Method for Manufacturing Alkaline Dry Battery] (First Embodiment) A method for manufacturing an alkaline dry battery according to a first embodiment of the present disclosure includes: (A) arranging a power generating element including a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode in a battery case having an opening; (B) a sealing unit including a negative electrode terminal plate, a negative electrode current collector joined to the negative electrode terminal plate, and a gasket, wherein the negative electrode current collector has a cylindrical body portion and a head portion protruding radially outward from one end of the cylindrical body portion in a length direction; and the gasket has a boss portion having a through hole penetrating the body portion and a head portion extending radially outward from the opening end of the battery case. (C) sealing the opening of a battery case in which a power generating element is disposed with the sealing unit, wherein in the fabrication of the sealing unit, the body of the negative electrode current collector is penetrated through the through hole of the boss portion so that the elastic modulus measured at the center of the outer peripheral surface of the boss portion is 1.50 GPa or more and 2.50 GPa or less. Note that hereinafter, the above (A) may be referred to as "disposing the power generating element," the above (B) may be referred to as "fabricating the sealing unit," and the above (C) may be referred to as "sealing the battery case."

[0067] (A) Arrangement of power generating elements The arrangement of the power generating elements can be carried out by placing a cylindrical positive electrode in a battery case having an opening, placing a cylindrical separator inside the cylindrical positive electrode, and filling the negative electrode inside the cylindrical separator.

[0068] A cylindrical positive electrode can be obtained, for example, by press-molding a positive electrode composite into a cylindrical shape. That is, a cylindrical positive electrode can be obtained as a positive electrode pellet. The positive electrode composite contains a positive electrode active material, a conductive agent, and an alkaline electrolyte, and may further contain a binder as needed. Examples of the positive electrode active material include manganese dioxide. Examples of the conductive agent include conductive carbon materials (carbon black (acetylene black), graphite, etc.). Examples of the alkaline electrolyte include an alkaline solution containing potassium hydroxide. After being placed (housed) in a battery case, the cylindrical positive electrode may be pressed so as to adhere to the inner wall of the battery case. Considering the need to adhere the cylindrical positive electrode to the inner wall of the battery case, if the battery case having an opening is a cylindrical case with a bottom, it is preferable that the positive electrode also be formed in a cylindrical shape.

[0069] The cylindrical separator can be obtained by processing, for example, a nonwoven fabric mainly composed of fibers or a microporous resin film into a cylindrical shape. The cylindrical separator is preferably arranged along the inner circumferential surface of the cylindrical positive electrode. Therefore, when the positive electrode is formed into a cylindrical shape as described above, it is preferable that the separator is also formed into a cylindrical shape. The cylindrical separator is preferably impregnated with an alkaline electrolyte. The impregnation of the cylindrical separator with the alkaline electrolyte can be carried out by placing the cylindrical separator inside the cylindrical positive electrode and then injecting the alkaline electrolyte into the inside of a battery case having an opening.

[0070] The negative electrode is preferably a gelled negative electrode. The gelled negative electrode can be obtained by mixing a negative electrode active material, a surfactant, a gelling agent, and an alkaline electrolyte. Examples of the negative electrode active material include zinc alloy powder. The zinc alloy may contain at least one element selected from the group consisting of indium, bismuth, and aluminum.

[0071] (B) Fabrication of Sealing Unit The sealing unit can be fabricated by joining one longitudinal end of the cylindrical body of the negative electrode current collector to the negative electrode terminal plate, and passing the body of the negative electrode current collector through the through hole of the boss portion so that the elastic modulus measured at the center of the outer peripheral surface of the boss portion is 1.50 GPa or more and 2.50 GPa or less.

[0072] One end of the cylindrical body in the longitudinal direction can be joined to the negative electrode terminal plate by electric welding. The negative electrode current collector preferably has a body and a head and is shaped like a nail. The head of the negative electrode current collector preferably has a joining surface that is joined to the negative electrode terminal plate. In this case, the negative electrode current collector is joined to the negative electrode terminal plate via the joining surface of the head. The negative electrode current collector can be obtained, for example, by pressing a brass wire into a predetermined shape (e.g., a nail shape). The negative electrode terminal plate can be obtained, for example, by pressing a nickel steel sheet or a tin-plated steel sheet into a predetermined shape.

[0073] The penetration of the body of the negative electrode current collector into the through-hole of the boss portion may be performed by adjusting the ratio of the outer diameter of the body of the negative electrode current collector to the inner diameter of the boss portion (hereinafter referred to as Ratio 1). For example, the penetration of the body of the negative electrode current collector into the through-hole of the boss portion may be performed by setting Ratio 1 in the range of 110% to 130%. As a result, as shown in the Examples section described later, the elastic modulus measured at the center of the outer peripheral surface of the boss portion can be set to a range of 1.50 GPa to 2.50 GPa. Furthermore, if it is difficult to adjust the range of the elastic modulus using Ratio 1 alone, the ratio of the outer diameter of the boss portion to the inner diameter of the boss portion (hereinafter referred to as Ratio 2) may be adjusted in addition to Ratio 1. For example, the penetration of the body of the negative electrode current collector into the through-hole of the boss portion may be performed by setting Ratio 1 in the range of 110% to 130% and then setting Ratio 2 in the range of 300% to 330%. As a result, as shown in the Examples section below, the elastic modulus measured at the center of the outer peripheral surface of the boss portion can be set to a range of 1.50 GPa to 2.50 GPa. The barrel portion of the negative electrode current collector can be penetrated into the through hole of the boss portion by press-fitting. The press-fitting conditions can be set appropriately taking into account the ratio 1.

[0074] (C) Sealing of the Battery Case The battery case can be sealed, for example, by inserting the other longitudinal end of the body of the negative electrode current collector into the negative electrode, and then crimping the open end of the battery case onto the peripheral edge of the negative electrode terminal plate via a gasket. After sealing the battery case, the outer peripheral surface of the battery case having the opening may be covered with an exterior label.

[0075] Second Embodiment A manufacturing method of an alkaline dry battery according to a second embodiment of the present disclosure includes, as in the first embodiment, (A) arrangement of a power generating element, (B) preparation of a sealing unit, and (C) sealing of a battery case, and in the preparation of the sealing unit (B), the sealing unit is annealed so that the elastic modulus measured at the center of the outer peripheral surface of the boss portion is 1.50 GPa or more and 2.50 GPa or less in a state in which the body portion of the negative electrode current collector is inserted into the through-hole of the boss portion. The first embodiment and the second embodiment differ in the preparation of the sealing unit (B), which will be described below.

[0076] (B) Fabrication of the Sealing Unit The sealing unit can be fabricated by joining one longitudinal end of the cylindrical body of the negative electrode current collector to the negative electrode terminal plate, and annealing the sealing unit so that the elastic modulus measured at the center of the outer peripheral surface of the boss portion is 1.50 GPa or more and 2.50 GPa or less with the body of the negative electrode current collector passing through the through hole of the boss portion. The annealing of the sealing unit will be described below. Note that the joining of the body portion to the negative electrode terminal plate is the same as in the first embodiment, and therefore will not be described again.

[0077] The annealing of the sealing unit is preferably carried out at a temperature ranging from 60°C to 120°C. The annealing of the sealing unit is preferably carried out for 0.5 hours or more, more preferably for 1 hour or more, and even more preferably for 1.5 hours or more. The sealing annealing may be carried out for 3 hours or less, or may be carried out for 2.5 hours or less. By carrying out annealing within the above temperature range and time, the elastic modulus measured at the center of the outer peripheral surface of the boss portion can be set to a range of 1.50 GPa to 2.50 GPa, as shown in the Examples section below.

[0078] The annealing of the sealing unit is performed with the body of the negative electrode current collector passing through the through-hole of the boss, and the ratio of the outer diameter of the body of the negative electrode current collector to the inner diameter of the boss (ratio 1) is preferably 105% or greater. By setting Ratio 1 in this range, it becomes easier to adjust the elastic modulus measured at the center of the outer peripheral surface of the boss after annealing to a range of 1.50 GPa to 2.50 GPa, as shown in the Examples section below.

[0079] (Additional Note) The above description discloses the following techniques.

[0080] (Technology 1) A battery comprising: a battery case having an opening; a power generating element housed in the battery case; and a sealing unit that seals the opening; the power generating element comprising a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode; the sealing unit comprising 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 having a cylindrical body and a head that protrudes radially outward from one end of the cylindrical body in the lengthwise direction; the gasket comprising a boss having a through hole penetrating the body, an outer periphery that contacts the open end of the battery case, and a connecting portion that connects the boss and the outer periphery, and is made of polypropylene resin; the head of the negative electrode current collector is located on one end side of the boss in the lengthwise direction; an elastic modulus measured at a central portion of an outer peripheral surface of the boss portion when the body portion is inserted through the through hole is 1.50 GPa or more and 2.50 GPa or less.

[0081] (Technology 2) The alkaline dry battery according to Technology 1, wherein the boss portion has a tapered shape that tapers from one end side to the other end side in the length direction, and a taper angle of the outer peripheral surface of the boss portion is 1° or more and 5° or less.

[0082] While the present invention has been described in terms of presently preferred embodiments, such disclosure should not be interpreted as limiting. Various changes and modifications will no doubt become apparent to those skilled in the art to which the present invention pertains upon reading the above disclosure. It is therefore intended that the appended claims be interpreted to cover all changes and modifications that do not depart from the true spirit and scope of the invention.

[0083] Hereinafter, the present disclosure will be specifically described based on examples and comparative examples, but the present disclosure is not limited to the following examples.

[0084] Example 1 (1) Preparation of Electrolyte (Alkaline Electrolyte) An alkaline electrolyte containing potassium hydroxide and zinc oxide was prepared. The concentration of potassium hydroxide in the alkaline electrolyte was 40% by mass, and the concentration of zinc oxide in the alkaline electrolyte was 7% by mass.

[0085] (2) Preparation of Positive Electrode Manganese dioxide (positive electrode active material) and graphite were mixed to obtain a mixture (powder mixture). The mixing ratio (mass ratio) of manganese dioxide to graphite was manganese dioxide:graphite = 100:6. Electrolytic manganese dioxide powder (average particle size (D50): 40 μm) was used as the manganese dioxide, and graphite powder (average particle size (D50): 8 μm) was used as the graphite.

[0086] The electrolytic solution prepared in (1) above was added to the powder mixture, thoroughly stirred and mixed, and then compression-molded into flakes to obtain a positive electrode composite. The mixing ratio (mass ratio) of the powder mixture to the electrolytic solution was powder mixture:electrolytic solution = 100:1.5.

[0087] The flake-shaped positive electrode composite was crushed to obtain a granular positive electrode composite, and then the granular positive electrode composite was classified using a 10-mesh sieve and a 100-mesh sieve into an undersized product on the 100-mesh sieve and an oversized product on the 100-mesh sieve. 3 g of this classified granular positive electrode composite was pressure-molded into a hollow cylindrical shape having dimensions of 13.5 mm outer diameter x 10.8 mm height to obtain a positive electrode pellet. Two positive electrode pellets were produced.

[0088] (3) Preparation of Negative Electrode A gelled negative electrode was obtained by mixing zinc alloy powder (negative electrode active material), surfactant, gelling agent, and electrolyte. The mixing ratio (mass ratio) of zinc alloy powder, surfactant, gelling agent, and electrolyte was zinc alloy powder:surfactant:gelling agent:electrolyte = 170:0.005:100:2.5. The zinc alloy powder used contained 0.02% by mass of indium, 0.01% by mass of bismuth, and 0.005% by mass of aluminum, with the remainder being zinc. The average particle size (D50) of the zinc alloy powder was 130 μm. The surfactant used was the anionic surfactant A described in the above embodiment section. The gelling agent used was a mixture of crosslinked polyacrylic acid and a partial sodium salt of crosslinked polyacrylic acid. The electrolyte used was the one prepared in (1) above.

[0089] (4) Assembly of an Alkaline Dry Battery: A bottomed cylindrical case (outer diameter 14 mm, cylindrical wall thickness 0.2 mm, height 50 mm) made of nickel-plated steel sheet was coated on its inner surface with Bunny Height (manufactured by Nippon Graphite Co., Ltd.) to form a carbon coating approximately 10 μm thick. This resulted in a battery case. Two positive electrode pellets were inserted vertically into the battery case, and pressure was applied to seal each positive electrode pellet to the inner wall of the battery case. In this way, a positive electrode consisting of two positive electrode pellets was formed. A bottomed cylindrical separator was placed inside the positive electrode, and then an alkaline electrolyte was injected into the battery case to impregnate the separator. The alkaline electrolyte prepared in (1) above was used. Next, 6.5 g of a gelled negative electrode was filled inside the separator.

[0090] The cylindrical separator with a bottom was constructed using a cylindrical separator and a base paper. The cylindrical separator and the base paper were made of a nonwoven fabric sheet (basis weight: 55 g / m) mainly composed of rayon fiber and polyvinyl alcohol fiber in a mass ratio of 1:1. ２ The thickness of the nonwoven fabric sheet used for the bottom paper was 0.3 mm. The cylindrical separator was formed by doubly winding two overlapping nonwoven fabric sheets each having a thickness of 0.1 mm.

[0091] The negative electrode current collector was formed by pressing common brass (Cu content: approximately 65% ​​by mass, Zn content: approximately 35% by mass) into a nail shape and then tin-plating the surface. The outer diameter D1 of the body of the negative electrode current collector was 1.40 mm. The head of the negative electrode current collector was electrically welded to a negative electrode terminal plate made of nickel-plated steel plate. The body of the negative electrode current collector was then press-fitted into the through-hole of the boss portion of a gasket made of polypropylene resin. In this way, a sealing unit consisting of the gasket, negative electrode terminal plate, and negative electrode current collector was produced.

[0092] Next, the sealing unit was placed in the opening of the battery case. At this time, the body of the negative electrode current collector was inserted into the negative electrode. The opening edge of the battery case was crimped to the peripheral edge of the negative electrode terminal plate via a gasket, sealing the opening of the battery case. The outer peripheral surface of the battery case was covered with an exterior label. In this way, the alkaline dry battery of Example 1 was produced.

[0093] As described above, the gasket used included a boss portion, an outer periphery, and a connecting portion connecting the boss portion and the outer periphery. The inner diameter D2 of the boss portion was 1.10 mm, and the outer diameter D3 of the boss portion was 3.80 mm. The taper angle θ of the outer periphery of the boss portion was 3°. The ratio of the outer diameter D1 of the body portion of the negative electrode current collector to the inner diameter D2 of the boss portion (D1 / D2 ratio) was 127%.

[0094] [Example 2] Except for setting the outer diameter D1 of the body of the negative electrode current collector to 1.45 mm, an alkaline dry battery according to Example 2 was obtained in the same manner as in Example 1. The D1 / D2 ratio was 132%.

[0095] An alkaline dry battery according to Example 3 was obtained in the same manner as in Example 1, except that the outer diameter D1 of the body portion of the negative electrode current collector was set to 1.25 mm and the outer diameter D3 of the boss portion was set to 3.50 mm. The D1 / D2 ratio was 114%.

[0096] An alkaline dry battery according to Example 4 was obtained in the same manner as in Example 1, except that the outer diameter D1 of the body of the negative electrode current collector was 1.15 mm, the inner diameter D2 of the boss was 0.90 mm, and the outer diameter D3 of the boss was 3.6 mm. The D1 / D2 ratio was 128%.

[0097] [Example 5] An alkaline dry battery according to Example 5 was obtained in the same manner as in Example 1, except that the outer diameter D1 of the body portion of the negative electrode current collector was set to 1.15 mm, the body portion of the negative electrode current collector was press-fitted into the through-hole in the boss portion of a gasket made of polypropylene resin, and then annealed at 80°C for 2 hours. The D1 / D2 ratio was 105%. The annealing was performed in a thermostatic oven at 80°C. After the annealing, the sealing unit was removed from the thermostatic oven and allowed to cool naturally in an environment of 15 to 20°C.

[0098] Example 6 An alkaline dry battery according to Example 6 was obtained in the same manner as in Example 5, except that the annealing temperature was set to 100°C.

[0099] Example 7 An alkaline dry battery according to Example 7 was obtained in the same manner as in Example 5, except that the annealing temperature was set to 120°C.

[0100] Comparative Example 1 An alkaline dry battery according to Comparative Example 1 was obtained in the same manner as in Example 5, except that the annealing treatment was not carried out.

[0101] Comparative Example 2 An alkaline dry battery according to Comparative Example 2 was obtained in the same manner as in Example 3, except that the outer diameter D3 of the boss portion was set to 3.80 mm.

[0102] [Comparative Example 3] Except for changing the outer diameter D1 of the body portion of the negative electrode current collector to 1.50 mm, an alkaline dry battery according to Comparative Example 3 was obtained in the same manner as in Example 1. The D1 / D2 ratio was 136%.

[0103] [Comparative Example 4] Except for changing the outer diameter D1 of the body portion of the negative electrode current collector to 1.55 mm, an alkaline dry battery according to Comparative Example 4 was obtained in the same manner as in Example 1. The D1 / D2 ratio was 141%.

[0104] Comparative Example 5 An alkaline dry battery according to Comparative Example 5 was obtained in the same manner as in Example 3, except that the outer diameter D3 of the boss portion was set to 3.20 mm.

[0105] Comparative Example 6 An alkaline dry battery according to Comparative Example 6 was obtained in the same manner as in Example 3, except that the taper angle θ on the outer peripheral surface of the boss portion was set to 0°.

[0106] Comparative Example 7 An alkaline dry battery according to Comparative Example 7 was obtained in the same manner as in Example 3, except that the taper angle θ on the outer peripheral surface of the boss portion was set to 6°.

[0107] <Evaluation> Elastic Modulus G The elastic modulus G of the central portion of the outer peripheral surface of the boss portion of each alkaline battery according to the example was determined according to the procedure described in the embodiment section above. The elastic modulus G was determined before the sealing unit was installed in the opening of the battery case. The results are shown in Table 1 below. Leakage Occurrence Ten alkaline batteries according to each example were prepared. Next, ten alkaline batteries according to each example were left in a thermostatic chamber at 80°C for three months. After three months, the number of alkaline electrolyte leaks observed in each of the ten alkaline batteries according to each example was visually checked. The results are shown in Table 1 below.

[0108]

[0109] From Table 1, it can be seen that the alkaline dry batteries according to Examples 1 to 7 had an elastic modulus G in the range of 1.50 GPa or more and 2.50 GPa or less, and none of them showed visible leakage of alkaline electrolyte. In contrast, the alkaline dry batteries according to Comparative Examples 1 to 7 had an elastic modulus G outside the range of 1.50 GPa or more and 2.50 GPa or less, and one or more of them showed visible leakage of alkaline electrolyte.

[0110] The alkaline dry battery according to the present disclosure can be used in applications where it is necessary to suppress leakage of alkaline electrolyte.

[0111] 1: Battery case 2: Positive electrode 3: Negative electrode 4: Separator 5: Gasket 5a: Boss portion, 5b: Outer periphery, 5c: Connecting portion 6: Negative electrode current collector 6a: Body portion, 6b: Head portion 7: Negative electrode terminal plate 7h: Gas vent hole 8: Exterior label 9: Sealing unit 10: Alkaline dry battery

Claims

1. An alkaline dry battery comprising: a battery case having an opening; a power generation element housed in the battery case; and a sealing unit for sealing the opening, wherein 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 negative electrode current collector joined to the negative electrode terminal plate, and a gasket, the negative electrode current collector has a cylindrical body portion and a head portion protruding radially outward from one end portion in the length direction of the cylindrical body portion, the gasket includes a boss portion having a through hole penetrating the body portion, an outer peripheral portion in contact with the opening end portion of the battery case, and a connecting portion connecting the boss portion and the outer peripheral portion, and is formed of a polypropylene resin, the head portion of the negative electrode current collector is disposed on one end side in the length direction of the boss portion, and when the body portion penetrates the through hole, the elastic modulus G measured at the central portion of the outer peripheral surface of the boss portion is 1.50 GPa or more and 2.50 GPa or less.

2. The alkaline dry battery according to claim 1, wherein the boss portion has a tapered shape that tapers from one end side to the other end side in the length direction, and the taper angle on the outer peripheral surface of the boss portion is 1° or more and 5° or less.

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