Alkaline dry battery

Abstract

An alkaline dry battery includes a battery case, a power generation element, and a sealing assembly. The sealing assembly is provided with a terminal plate, a current collector joined to the terminal plate, and a gasket. The current collector has a cylindrical main body part. The gasket is provided with a central tube section, an outer peripheral section, and a connecting section. The connecting portion has a convex curved portion bulging toward the bottom of the battery case, a first inclined portion extending from the central cylindrical portion to the curved portion, and a second inclined portion extending from the curved portion to the outer peripheral portion side. The gasket contains a polypropylene resin, and a rubber component is dispersed inside the gasket. The rubber component abundance ratio R (%) with respect to the total of the polypropylene resin and the rubber component and the interior angle [theta] 1 (degree) formed by the first inclined portion and the second inclined portion satisfy 3 < = R < = 20 and 0.59 R + 128 < = [theta] 1 < = 0.59 R + 163.

Description

Technical Field

[0001] The present invention relates to an alkaline dry cell. Background Art

[0002] Alkaline dry batteries (alkaline manganese dry batteries) are widely used because they have a larger battery capacity than manganese dry batteries and can draw a large current. Alkaline dry batteries generally have a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and an alkaline electrolyte. The positive electrode contains manganese dioxide as a positive electrode active material. In order to improve the characteristics of alkaline dry batteries, various proposals have been proposed in the past.

[0003] Patent document 1 discloses a gasket, "a resin-made sealing gasket 33 for alkaline batteries, comprising a peripheral filler portion 36 and a partition portion 37, wherein the peripheral filler portion 36 is sandwiched between the opening of a metal battery can 11 that accommodates a power generation element 20 and also serves as a positive terminal and the negative terminal 32 in a compressed state to airtightly seal the opening, and the partition portion 37 isolates the inner space of the negative terminal from the storage space of the power generation element, and a thin-walled portion 38 is formed in the partition portion in the shape of a groove, which breaks in advance due to the increase in air pressure in the storage space to function as a safety valve, the groove direction of the thin-walled portion 38 is the same direction as the resin orientation of the gasket, and the cantilever beam impact value of the resin forming the gasket is in the range of 20 to 60 J / m". In order to relieve the stress when the opening of the battery can is clamped to the gasket, the partition portion is bent in a manner that makes the bottom side of the battery can convex.

[0004] Existing patent literature

[0005] Patent Literature

[0006] Patent Document 1: International Publication No. 2004 / 077592 Summary of the invention

[0007] The gasket of alkaline dry cell batteries has the function of an explosion-proof valve. When the internal pressure of the battery reaches a specified value, the thin wall of the gasket breaks and the pressure is released. When polypropylene resin is used as the material of the gasket, the working pressure of the explosion-proof valve tends to increase due to the high elongation of polypropylene resin. Therefore, the rubber component is dispersed in the gasket to stabilize the working pressure of the explosion-proof valve.

[0008] However, the rubber component dispersed in the gasket may be broken by the increase of the internal pressure of the battery that does not reach the working pressure, forming gaps. Since such gaps form a migration path for the electrolyte, electrolyte leakage may occur. Such leakage is particularly likely to occur in the gasket at the portion where stress is likely to concentrate.

[0009] An alkaline dry battery according to one aspect of the present invention comprises: a battery case having an opening and a bottom on the opposite side of the opening, a power generation element housed in the battery case, and a sealing assembly for sealing the opening of the battery case. The sealing assembly comprises a terminal plate, a current collector joined to the terminal plate, and a gasket. The current collector has a cylindrical main body extending in the axial direction. The gasket comprises a central cylinder through which the main body of the current collector passes, an outer peripheral portion sandwiched between the peripheral portion of the terminal plate and the opening end of the battery case facing the opening, and a connecting portion connecting the central cylinder to the outer peripheral portion. The connecting portion comprises a curved portion that is convex in a manner of swelling toward the bottom of the battery case, a first inclined portion extending from the central cylinder to the curved portion, and a second inclined portion extending from the curved portion to the side of the outer peripheral portion. The gasket comprises a polypropylene resin, and a rubber component is dispersed inside the gasket. The abundance ratio R (%) of the rubber component relative to the total of the polypropylene resin and the rubber component and the inner angle θ1 (°) formed by the first inclined portion and the second inclined portion satisfy 3≤R≤20, 0.59×R+128≤θ1≤0.59×R+163.

[0010] According to the present invention, it is possible to provide an alkaline dry battery in which a polypropylene resin in which a rubber component is dispersed is used in a gasket and in which leakage is suppressed. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 This is a front view showing a section of a part of an alkaline dry battery according to one embodiment.

[0012] Figure 2 This is a cross-sectional view showing an example of a main part of an alkaline dry battery according to an embodiment.

[0013] Figure 3A This is a plan view of an example of a gasket for an alkaline dry battery according to one embodiment.

[0014] Figure 3B yes Figure 3A An enlarged view of a rectangular area v of the pad is shown.

[0015] Figure 3C yes Figure 3B A cross-sectional view of the gasket taken along line C1-C1 is shown.

[0016] Figure 3D yes Figure 3B A cross-sectional view of the gasket taken along line C2-C2 is shown.

[0017] Figure 4 This is a diagram showing the correspondence between the internal angle θ1 and the abundance ratio R of the rubber component of the alkaline dry battery according to one embodiment, and the evaluation results of Examples and Comparative Examples. DETAILED DESCRIPTION

[0018] Hereinafter, the embodiments of the present invention will be described with examples, but the present invention is not limited to the examples described below. In the following description, specific numerical values ​​and materials are sometimes exemplified, but other numerical values ​​and other materials may also be applied as long as the invention of the present invention can be implemented. In this specification, the description of "numerical value A to numerical value B" includes numerical value A and numerical value B, and may be renamed as "numerical value A or more and numerical value B or less". In the following description, when the lower limit and upper limit of numerical values ​​regarding specific physical properties, conditions, etc. are exemplified, as long as the lower limit is not above the upper limit, any of the exemplified lower limits may be arbitrarily combined with any of the exemplified upper limits.

[0019] In addition, the present invention includes a combination of matters recorded in two or more claims arbitrarily selected from a plurality of claims recorded in the scope of the attached claims. That is, as long as no technical contradiction occurs, matters recorded in two or more claims arbitrarily selected from a plurality of claims recorded in the scope of the attached claims may be combined.

[0020] In the following description, the term “comprising” or “including” includes expressions such as “comprising (or including)”, “consisting essentially of”, and “consisting of”.

[0021] The type of dry cell is not particularly limited, and for example, any of single 1 type to single 6 type (Japanese battery model) may be used.

[0022] (Alkaline dry cell batteries)

[0023] Alkaline dry batteries include: a battery case with an opening, a power generation element contained in the battery case, and a sealing assembly for sealing the opening. The sealing assembly includes a terminal plate, a current collector joined to the terminal plate, and a gasket. The battery case has a cylindrical portion and a bottom. The power generation element includes a positive electrode, a negative electrode, a spacer disposed between the positive electrode and the negative electrode, and an alkaline electrolyte. The terminal plate not only seals the opening of the battery case but also functions as a negative terminal. The current collector has a cylindrical main body.

[0024] The gasket has a central tube portion through which the main body of the current collector passes, an outer peripheral portion sandwiched between the peripheral portion of the terminal plate and the open end of the battery case, a connecting portion connecting the central tube portion and the outer peripheral portion, and a thin-walled portion formed in a groove shape. The outer peripheral portion is annular and wraps the peripheral portion of the terminal plate from the outer edge side. The connecting portion is also annular. The central tube portion, the outer peripheral portion, and the connecting portion are integrally formed.

[0025] The connecting portion has a curved portion that is convex in a manner that bulges toward the bottom of the battery case. The connecting portion can be divided into a first inclined portion and a second inclined portion with the curved portion as a boundary. The first inclined portion is a portion extending from the central barrel to the curved portion. The second inclined portion is a portion extending from the curved portion to the peripheral portion side. The connecting portion is inclined as a whole in a manner that the end portion on the peripheral portion side is closer to the bottom side of the battery case relative to the end portion on the central barrel side. The connecting portion extends, for example, from the end portion of the central barrel on a side away from the bottom of the battery case, and continues to the end portion of the peripheral portion on a side close to the bottom of the battery case.

[0026] The gasket contains a polypropylene resin. The polypropylene resin is a resin composed of polypropylene in an amount of 95% or more and 100% or less by mass. The polypropylene resin may contain resin components other than polypropylene, antioxidants, etc. A rubber component is dispersed inside the gasket to form a sea-island structure in which the polypropylene resin as the main component of the gasket is the sea part (matrix) and the rubber component is the island part. It should be noted that although the gasket may contain materials other than the polypropylene resin and the rubber component (e.g., filler), generally, for example, more than 90% by mass of the gasket is composed of the polypropylene resin and the rubber component.

[0027] As the internal pressure of the battery rises, stress is concentratedly applied to the curved portion of the connecting portion, and the connecting portion is deformed in such a way that the first inclined portion and the second inclined portion face the same direction. At this time, the rubber component present in the connecting portion is subjected to compressive stress. When the internal pressure of the battery rises further, the bending of the connecting portion is reversed, and the connecting portion is bent in a convex shape that bulges toward the opening of the battery case. At this time, the rubber component present in the connecting portion is subjected to tensile stress. The deformation of the rubber component reaches a maximum at the curved portion. If the shape of the rubber component is spherical, the rubber component in the connecting portion becomes an elongated shape and breaks. As a result, a gap is formed in the curved portion. Since the gap forms a movement path for the electrolyte, it becomes a cause of leakage. Such a phenomenon may occur even with an internal pressure increase to a degree that may occur during normal use.

[0028] The smaller the internal angle θ1 formed by the first inclined portion and the second inclined portion of the connecting portion (i.e., the larger the bend), and the larger the existence ratio R of the rubber component dispersed in the gasket, the easier it is for voids to be formed. To suppress the formation of voids, it is sufficient to increase the internal angle θ1 formed by the first inclined portion and the second inclined portion as much as possible without hindering the stability of the working pressure of the explosion-proof valve, or to reduce the existence ratio R of the rubber component dispersed in the gasket as much as possible.

[0029] In the present invention, the internal angle θ1 formed by the first inclined portion and the second inclined portion is set within a specific range according to the existence ratio R of the rubber component dispersed in the gasket. As a result, when the internal pressure of the battery is below the operating pressure of the explosion-proof valve, the formation of voids and the leakage of electrolyte caused by the voids are suppressed, and the explosion-proof valve is operated when the internal pressure of the battery reaches a predetermined pressure. That is, an alkaline dry battery with excellent operating performance of the explosion-proof valve and highly suppressed leakage can be realized.

[0030] Specifically, the abundance ratio R (%) of the rubber component relative to the total of the polypropylene resin and the rubber component and the internal angle θ1 (°) formed by the first inclined portion and the second inclined portion satisfy the following equations (1) and (2).

[0031] 3≤R≤20 (1)

[0032] 0.59×R+128≤θ1≤0.59×R+163 (2)

[0033] When R and θ1 satisfy equations (1) and (2), if the battery internal pressure is lower than the operating pressure of the explosion-proof valve, leakage of electrolyte due to the formation of voids can be suppressed. On the other hand, if the battery internal pressure reaches a predetermined pressure, the explosion-proof valve operates.

[0034] If the negative electrode expands excessively during discharge, the gasket is compressed, and greater stress is applied to the gasket. In view of this, when the acute angle (angle less than 90°) θ2 formed by the axial direction of the central cylinder and the first inclined portion is set to 20° or more, it is easy to alleviate the stress concentration on the curved portion. That is, even in a situation where leakage is more likely to occur, leakage can be suppressed.

[0035] In addition, if the positive electrode expands excessively during discharge, the gasket is compressed, and greater stress is applied to the gasket. In this regard, when W / H ≥ 1.0 is satisfied, it is easy to relieve stress concentration on the curved portion. That is, leakage can be suppressed even in a situation where leakage is more likely to occur.

[0036] Here, W is the width of the connecting portion in the radial direction of the central cylinder, and H is the height H of the connecting portion in the axial direction of the central cylinder. That is, when the position of the most central cylinder side on the upper surface side (opening side) of the first inclined portion is X and the position of the most peripheral cylinder side on the upper surface side (opening side) of the second inclined portion is Y, the difference between the radial position of the central cylinder at position X and the radial position of position Y is the width W. In addition, the difference between the axial position of the central cylinder at position X and the axial position of position Y is the height H. It can be said that the rectangle having two sides parallel to the radial direction of the central cylinder and two sides parallel to the axial direction of the central cylinder, and the straight line XY connecting position X and position Y as a diagonal line, is preferably a square or a rectangle with a large radial width.

[0037] Examples of the rubber component dispersed in the gasket include natural rubber, ethylene-propylene copolymer, ethylene-propylene-diene copolymer, butadiene polymer, butadiene-styrene copolymer, butadiene-acrylonitrile copolymer, chloroprene polymer, isoprene polymer, styrene-isoprene copolymer, isobutylene polymer, isobutylene-butadiene copolymer, isobutylene-isoprene copolymer, acrylate polymer, thiol rubber, polysulfide rubber, polyurethane rubber, polyether rubber, epichlorohydrin rubber, and the like.

[0038] A preferred example of the gasket is a gasket in which a rubber component such as an ethylene-propylene-diene copolymer is dispersed in a matrix of a polypropylene resin.

[0039] It should be noted that the rubber component contained in the gasket can be identified by various analytical methods, such as pyrolysis gas chromatography-mass spectrometry (Py-GC / MS), NMR, thermogravimetric analysis (TG), evolved gas analysis (EGA), and the like.

[0040] The abundance ratio R of the rubber component relative to the total of the polypropylene resin and the rubber component is determined by the method shown below.

[0041] First, the alkaline dry cell is disassembled and the gasket is taken out to obtain a sample of the gasket. Usually, the rubber component is evenly dispersed in the gasket, and the content ratio of the rubber component is the same in any area in the gasket. Avoid the outer peripheral part compressed between the peripheral part of the terminal plate and the opening end of the battery case, and take the sample from the part with small stress load such as the central cylinder. Make a cross section of the collected sample and take a cross-sectional image using a scanning electron microscope (SEM). The magnification of the SEM is, for example, 2000 times.

[0042] Then, the cross-sectional image is binarized using image processing software (ImageJ) with a threshold value (Threshold) of 110. By using the binarization process, the rubber component of the cross-sectional image is converted to white, and the components other than the rubber component are converted to black. However, in actual SEM images, sometimes only the outline of the rubber component is displayed, and the inside of the outline is displayed in a tone roughly the same as that of the components other than the rubber component. In this case, in order to treat the inside of the outline as the rubber component, the binarized image is corrected while comparing it with the actual SEM image. For example, the area inside the outline corresponding to the rubber component is painted white. The ratio r of the area of ​​the rubber component (white part) in the obtained binarized image to the area of ​​the entire binary image is calculated. The percentage value (%) of the ratio r is calculated as the existence ratio R of the rubber component (R = r × 100).

[0043] Regarding the thickness of the connecting portion, in the case of single type 1 (Japanese battery model), it is, for example, 0.6 to 0.8 mm, in the case of single type 2 (Japanese battery model), it is, for example, 0.4 to 0.6 mm, and in the case of single type 3 (Japanese battery model) and single type 4 (Japanese battery model), it is, for example, 0.2 to 0.5 mm.

[0044] The axial height of the central tube portion is, for example, 7 to 10 mm in the case of the single 1 type, 6.5 to 9.5 mm in the case of the single 2 type, and 2 to 6 mm in the case of the single 3 type and the single 4 type.

[0045] Figure 1 This is a front view showing a portion of an alkaline dry battery 10 according to an embodiment of the present invention in cross section. Figure 2 Yes Figure 1 FIG. 1 is an enlarged cross-sectional view of a main part of an alkaline dry battery 10.

[0046] The cylindrical alkaline dry battery 10 includes a battery case 1, a positive electrode 2 disposed in the battery case 1, a negative electrode (gel negative electrode) 3, a separator 4, and an alkaline electrolyte (not shown). The alkaline dry battery 10 has an inside-out structure.

[0047] The battery case 1 is a bottomed cylindrical case having an opening 1a and a bottom 1b on the opposite side of the opening 1a, and functions as a positive electrode terminal. The positive electrode 2 is a hollow cylindrical shape and is arranged in contact with the inner wall of the battery case 1. The negative electrode 3 is arranged in the hollow part of the positive electrode 2. The separator 4 is arranged between the positive electrode 2 and the negative electrode 3.

[0048] The separator 4 is composed of a cylindrical separator 4a and a backing paper 4b. The separator 4a is arranged along the inner surface of the hollow part of the positive electrode 2 to separate the positive electrode 2 from the negative electrode 3. The backing paper 4b is arranged at the bottom of the hollow part of the positive electrode 2 to separate the negative electrode 3 from the battery case 1.

[0049] The opening 1a of the battery case 1 is sealed by a sealing assembly 9. The sealing assembly 9 includes a gasket 5, a negative electrode collector 6, and a negative terminal plate 7 that functions as a negative terminal. The negative electrode collector 6 has a nail shape having a head 6a and a cylindrical main body 6b. The main body 6b of the negative electrode collector 6 is inserted into the through hole 5e provided in the central cylindrical portion 5a of the gasket 5, and is inserted into the negative electrode 3. The head 6a of the negative electrode collector 6 is welded to the flat portion 7a in the center of the negative terminal plate 7.

[0050] The opening end 1c of the battery case 1 facing the opening 1a is clamped to the peripheral edge 7b (folded edge) of the negative terminal plate 7 via the outer peripheral portion of the gasket 5. The outer surface of the battery case 1 is covered with an outer packaging label 8. The battery case 1, the gasket 5 and the negative terminal plate 7 constitute a battery cover. The positive electrode 2, the negative electrode 3, the separator 4 and the alkaline electrolyte are power generation elements arranged in the battery cover.

[0051] like Figure 2 As shown, the gasket 5 includes a central tube 5a, a peripheral portion 5b, and a connecting portion 5c connecting the central tube 5a and the peripheral portion 5b. The central tube 5a has a through hole 5e, and the main body 6b of the negative electrode collector 6 is inserted into the through hole 5e. The peripheral portion 5b is sandwiched between the peripheral portion 7b of the negative terminal plate 7 and the open end 1c of the battery case 1, and has the function of sealing the negative terminal plate 7 and the open end 1c of the battery case 1.

[0052] The central tube portion 5a and the peripheral portion 5b of the gasket 5 are continuous via the connecting portion 5c. The connecting portion 5c is continuous with the central tube portion 5a at the upper side of the central tube portion 5a (the side away from the bottom of the battery case), and is continuous with the peripheral portion 5b at the lower side of the peripheral portion 5b (the side close to the bottom of the battery case). Therefore, the boundary position of the connecting portion 5c with the central tube portion 5a and the boundary position of the connecting portion 5c with the peripheral portion 5b are located on the opposite side in the axial direction of the central tube portion 5a, and the connecting portion 5c is inclined relative to the axial direction of the central tube portion 5a.

[0053] The connection portion 5c has a curved portion 5d convexly bulging toward the bottom of the battery case 1. The connection portion 5c has a first inclined portion 5c1 extending from the central tube portion 5a to the curved portion 5d and a second inclined portion 5c2 extending from the curved portion 5d to the outer peripheral portion 5b.

[0054] The gasket 5 contains a polypropylene resin 5m1 and a rubber component 5m2 dispersed in the polypropylene resin 5m1. The polypropylene resin 5m1 is a resin composed of polypropylene in an amount of 95% by mass or more and 100% or less. The polypropylene resin 5m1 may contain resin components other than polypropylene, antioxidants, etc. The gasket 5 has a sea-island structure composed of a sea portion (matrix) and an island portion, wherein the sea portion (matrix) is formed of the polypropylene resin 5m1 and is the main component of the gasket 5, and the island portion is formed of the rubber component 5m2. It should be noted that although the gasket 5 may contain materials other than the polypropylene resin 5m1 and the rubber component 5m2 (e.g., fillers), it is preferred that most of the gasket 5, for example, 90% by mass or more, is composed of the polypropylene resin 5m1 and the rubber component 5m2.

[0055] As the internal pressure of the battery 10 rises, stress is concentratedly applied to the curved portion of the connecting portion 5c, and the connecting portion 5c is deformed in such a way that the first inclined portion 5c1 and the second inclined portion 5c2 face the same direction. At this time, the rubber component 5m2 present in the connecting portion 5c is subjected to compressive stress. When the internal pressure of the battery 10 further rises, the bending of the connecting portion 5c is reversed, and the connecting portion 5c is bent in a convex shape that bulges toward the opening 1a of the battery case 1. At this time, the rubber component 5m2 present in the connecting portion 5c is subjected to tensile stress. The deformation amount of the rubber component 5m2 reaches the maximum at the curved portion of the connecting portion 5c. If the shape of the rubber component 5m2 is spherical, the rubber component 5m2 becomes elongated in the connecting portion 5c, and there is a possibility of fracture. As a result, a gap is formed in the curved portion of the connecting portion 5c.

[0056] In the connecting portion 5c, the internal angle θ1 formed by the first inclined portion 5c1 and the second inclined portion 5c2, the acute angle θ2 formed by the first inclined portion 5c1 and the axial direction Da of the central tube portion 5a, and the ratio of the width W in the radial direction Dr of the connecting portion 5c to the height H in the axial direction Da of the connecting portion 5c are controlled according to the abundance ratio R of the rubber component: W / H (refer to Figure 2 ), thereby realizing an alkaline dry battery 10 in which the explosion-proof valve is activated when the internal pressure of the battery reaches a predetermined pressure while suppressing the leakage of the electrolyte due to the formation of voids.

[0057] Figure 3A It is a top view of the pad 5. Figure 3B for Figure 3A An enlarged view of a rectangular area v of the pad 5 is shown. Figure 3C for Figure 3B A cross-sectional view of the gasket 5 taken along line C1 - C1 is shown. Figure 3D for Figure 3B 2 is a cross-sectional view of the gasket 5 at the line C2-C2 shown in FIG. A thin-walled portion 5v having a groove shape and being partially thin is formed as an explosion-proof valve at the connecting portion 5c of the gasket 5. In order to make the explosion-proof valve operate stably, it is preferable to form the thin-walled portion 5v continuously from the bent portion. The thin-walled portion 5v has a groove shape extending in the radial direction Dr passing through the center 5f of the central cylindrical portion 5a and having a V-shaped cross section. The thin-walled portion 5v is formed in the radial direction Dr across the bent portion 5d and has a portion 5v1 extending in the radial direction Dr through the width w1 of the first inclined portion 5c1 and a portion 5v2 extending in the radial direction Dr through the width w2 of the second inclined portion 5c2.

[0058] In this case, the thickness T of the groove-shaped thin-walled portion 5v is preferably 100 μm to 300 μm, the widths w1 and w2 are preferably 100 μm to 300 μm, and the V-shaped notch angle α is preferably 40° to 60°. The length of the groove-shaped thin-walled portion 5v is preferably 50% to 100% of the length of the connecting portion 5c in the radial direction Dr. The widths w1 and w2 may be the same or different.

[0059] It should be noted that the present invention is not limited to the above-mentioned examples, and two or more groove-shaped thin-walled portions may be formed radially. The thin-walled portion may also be formed in a ring shape along the curved portion. The thin-walled portion is configured such that when the internal pressure of the battery reaches an abnormally high value, the thin-walled portion breaks starting from the curved portion where stress is concentrated, and the internal gas is discharged.

[0060] Hereinafter, examples of other components of the alkaline dry battery of the present invention will be described.

[0061] (positive electrode)

[0062] The positive electrode contains manganese dioxide as a positive electrode active material. The positive electrode usually contains a positive electrode active material and a conductive material, and further contains a binding material as needed. The positive electrode can be formed by pressurizing the positive electrode mixture into a cylindrical body (positive electrode pellets). The positive electrode mixture, for example, contains a positive electrode active material, a conductive material, an alkaline electrolyte, and further contains a binding material as needed. After the cylindrical body is accommodated in the shell body, it can be pressurized in a manner that is closely fitted to the inner wall of the shell body.

[0063] A preferred example of manganese dioxide as the positive electrode active material is electrolytic manganese dioxide, but natural manganese dioxide and chemical manganese dioxide may also 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.

[0064] The average particle size (D50) of the manganese dioxide powder may be, for example, in the range of 25 μm to 60 μm in order to ensure the filling property of the positive electrode and the diffusibility of the electrolyte in the positive electrode. It should be noted that D50 in this specification is the median diameter at which the cumulative value of the volume-based particle size distribution reaches 50%.

[0065] From the viewpoint of formability and suppression of positive electrode expansion, the BET specific surface area of ​​manganese dioxide can be, for example, 20 m 2 / g~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.

[0066] The conductive material may be a conductive carbon material. Examples of conductive carbon materials include carbon black (acetylene black, etc.), graphite, etc. Examples of graphite include natural graphite, artificial graphite, etc. The conductive material may be a powdered material. The average particle size (D50) of the conductive material may be in the range of 3 μm to 20 μm. The content of the conductive material in the positive electrode may be in the range of 3 to 10 parts by mass (e.g., 5 to 9 parts by mass) relative to 100 parts by mass of manganese dioxide.

[0067] In order to absorb the hydrogen generated inside the battery, a silver compound can be added to the positive electrode. Examples of silver compounds include silver oxide (Ag2O, AgO, Ag2O3, etc.), silver nickel composite oxide (AgNiO2), etc.

[0068] (negative electrode)

[0069] The negative electrode contains a powder of a zinc alloy as a negative electrode active material. From the viewpoint of corrosion resistance, the zinc alloy may contain at least one selected from indium, bismuth and aluminum. The indium content in the zinc alloy may be, for example, in the range of 0.01 mass % to 0.1 mass %. The bismuth content in the zinc alloy may be, for example, in the range of 0.003 mass % to 0.02 mass %. The aluminum content in the zinc alloy may be, for example, in the range of 0.001 mass % to 0.03 mass %. Regarding the content of elements other than zinc in the zinc alloy, from the viewpoint of corrosion resistance, it may be in the range of 0.025 mass % to 0.08 mass %.

[0070] The average particle size (D50) of the zinc alloy powder can be in the range of 100 μm to 200 μm (e.g., 110 μm to 160 μm) from the viewpoint of the filling property of the negative electrode and the diffusibility of the electrolyte in the negative electrode. It should be noted that in this specification, the average particle size is the median diameter (D50) at which the cumulative volume reaches 50% in the volume-based particle size distribution. The median diameter is obtained, for example, using a laser diffraction / scattering particle size distribution measuring device.

[0071] The negative electrode may further include a gelling agent, a surfactant and an electrolyte on the basis of the zinc alloy powder. The negative electrode may be formed by mixing the zinc alloy powder, the gelling agent, the surfactant and the electrolyte. From the viewpoint of making the additive (gelling agent, surfactant, etc.) more uniformly dispersed in the negative electrode, the additive is preferably added in advance to the electrolyte used when the negative electrode is prepared. The electrolyte may use the electrolyte (alkaline electrolyte) described later.

[0072] In order to improve the corrosion resistance of the negative electrode, a compound containing a metal having a high hydrogen overvoltage, such as indium or bismuth, may be appropriately added.

[0073] (Negative electrode collector)

[0074] The negative electrode current collector may be made of metal (single metal or alloy). The negative electrode current collector preferably includes copper, or may be an alloy including copper and zinc (such as brass). The negative electrode current collector may be plated with tin or the like as required.

[0075] (Spacer)

[0076] Nonwoven fabrics mainly composed of fibers, microporous films made of resins, etc. are used as spacers. Examples of fiber materials include cellulose, polyvinyl alcohol, etc. Nonwoven fabrics can be formed by mixing cellulose fibers with polyvinyl alcohol fibers, or by mixing rayon fibers with polyvinyl alcohol fibers. Examples of materials for microporous films include resins such as cellophane and polyolefins. The thickness of the spacer can be in the range of 200μm to 300μm. When the spacer is thin, multiple spacers can be overlapped and adjusted to the above thickness.

[0077] (Alkaline electrolyte)

[0078] For example, an alkaline aqueous solution containing potassium hydroxide is used as the alkaline electrolyte. The concentration of potassium hydroxide in the alkaline electrolyte is preferably in the range of 30 to 50 mass % (for example, in the range of 30 to 40 mass %). The alkaline electrolyte may contain lithium hydroxide (LiOH), sodium hydroxide (NaOH), cesium hydroxide (CsOH), rubidium hydroxide (RbOH), etc.

[0079] The alkaline electrolyte may contain a surfactant. By using a surfactant, the dispersibility of the negative electrode active material particles can be improved. The surfactant may be the surfactant exemplified in the negative electrode. The content of the surfactant in the alkaline electrolyte is usually in the range of 0 to 0.5 mass % (e.g., 0 to 0.2 mass %).

[0080] (Battery cover)

[0081] The battery cover comprises a battery case 1, a gasket of a sealing assembly that seals the opening 1a, and a negative terminal plate. The battery case is, for example, a metal case with a bottomed cylindrical shape. The metal case is, for example, a nickel-plated steel plate. In order to reduce the contact resistance between the positive electrode and the battery case, the inner surface of the battery case may be coated with a carbon film. The negative terminal plate may be formed of the same material as the metal case, for example, a nickel-plated steel plate.

[0082] The method of assembling the alkaline dry battery 10 is not particularly limited, and existing techniques may be applied as needed. For example, the alkaline dry battery 10 may be assembled using the steps described in the following embodiments.

[0083] Hereinafter, the alkaline dry battery of the present invention will be described in further detail based on examples.

[0084] 《Examples 1 to 14, Comparative Examples 1 to 15》

[0085] Follow the steps (1) to (3) below to create Figure 1 The single 3-shaped cylindrical alkaline dry cell (LR6) is shown.

[0086] (1) Preparation of positive electrode

[0087] Graphite powder (average particle size (D50) 8 μm) as a conductive agent is added to electrolytic manganese dioxide powder (average particle size (D50) 35 μm) as a positive electrode active material to obtain a mixture. The mass ratio of electrolytic manganese dioxide powder to graphite powder is set to 94:6. An alkaline electrolyte is added to the mixture, and after sufficient stirring, it is compressed into a thin sheet to obtain a positive electrode mixture. The mass ratio of the mixture to the alkaline electrolyte is set to 100:3. The alkaline electrolyte uses an electrolyte in which zinc oxide is added to a potassium hydroxide aqueous solution. The concentration of potassium hydroxide in the alkaline electrolyte is set to 40% by mass. The concentration of zinc oxide in the alkaline electrolyte is set to 7% by mass.

[0088] The flaky positive electrode mixture was crushed into particles, which were classified using a sieve, and 6 g of the particles classified using a 10-100 mesh sieve were press-formed into a predetermined hollow cylindrical shape with an outer diameter of 13.5 mm to prepare two positive electrode pellets.

[0089] (2) Preparation of negative electrode

[0090] A zinc alloy powder (average particle size (D50) 130 μm) as a negative electrode active material, potassium fluoride as a fluoride, an alkaline electrolyte and a gelling agent are mixed to obtain a gelled negative electrode 3. A zinc alloy containing 0.02 mass % of indium, 0.01 mass % of bismuth and 0.005 mass % of aluminum is used as a zinc alloy. An alkaline electrolyte uses an electrolyte in which zinc oxide is added to a potassium hydroxide aqueous solution. The concentration of potassium hydroxide in the alkaline electrolyte is set to 35 mass %. The concentration of zinc oxide in the alkaline electrolyte is set to 5 mass %. A mixture of cross-linked branched polyacrylic acid and highly cross-linked chain polyacrylate sodium is used as a gelling agent. The mass ratio of the negative electrode active material to the alkaline electrolyte to the gelling agent is set to 170:100:2.5. The content of potassium fluoride in the negative electrode is set to 0.5 mass parts per 100 mass parts of the electrolyte.

[0091] (3) Assembly of alkaline dry batteries

[0092] Varniphite made by Nippon Graphite Co., Ltd. is applied on the inner surface of a bottomed cylindrical battery case (outer diameter 14 mm, wall thickness of the cylindrical part 0.2 mm, height 50 mm) made of nickel-plated steel plate to form a carbon film with a thickness of about 10 μm, thereby obtaining a battery case 1. Two positive electrode pellets are inserted longitudinally into the battery case 1 to form a positive electrode 2 in a state of close contact with the inner wall of the battery case 1. After the bottomed cylindrical separator 4 is arranged on the inner side of the positive electrode 2, an alkaline electrolyte is injected to impregnate the separator 4. Thereafter, 6.5 g of the gel-like negative electrode 3 is filled on the inner side of the separator 4. The alkaline electrolyte uses an electrolyte in which zinc oxide is added to a potassium hydroxide aqueous solution. The concentration of potassium hydroxide in the alkaline electrolyte is set to 35% by mass. The concentration of zinc oxide in the alkaline electrolyte is set to 5% by mass.

[0093] The bottomed cylindrical spacer 4 is composed of a cylindrical spacer and a base paper. The cylindrical spacer and the base paper are made of a non-woven fabric sheet (weight 55 g / m2) 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 base paper was 0.30 mm. The cylindrical spacer was formed by rolling a member having two layers of nonwoven fabric sheets having a thickness of 0.1 mm stacked on top of each other.

[0094] After ordinary brass (Cu content: about 65 mass%, Zn content: about 35 mass%) is pressed into a nail shape, the surface is tinned to obtain a negative electrode collector 6. The diameter of the main body 6b of the negative electrode collector 6 is set to 1.15 mm. The head 6a of the negative electrode collector 6 is electrically welded to the negative terminal plate 7 made of nickel-plated steel plate. Thereafter, the main body 6b of the negative electrode collector 6 is pressed into the through hole 5e of the central cylinder of the gasket 5 composed of a polypropylene resin in which ethylene-propylene-diene polymer (EPDM) is dispersed as a rubber component. In this way, a sealing assembly consisting of the gasket 5, the negative terminal plate 7 and the negative electrode collector 6 is produced.

[0095] Then, the sealing assembly is set at the opening 1a of the battery case 1. At this time, the main body 6b of the negative electrode collector 6 is inserted into the negative electrode 3. The opening end 1c of the battery case 1 is clamped to the peripheral edge 7b of the negative terminal plate 7 via the gasket 5, and the opening 1a of the battery case 1 is sealed. The outer surface of the battery case 1 is covered with an outer packaging label 8. In this way, an alkaline dry battery is manufactured.

[0096] As described above, the gasket 5 includes a central tube 5a, an outer peripheral portion 5b, and a connecting portion 5c connecting the central tube 5a and the outer peripheral portion 5b. A groove-shaped thin-walled portion (explosion-proof valve) is formed in the connecting portion 5c across the curved portion 5d. Gaskets 5 having different structures of the connecting portion 5c are prepared. Specifically, the combination of the inner angle θ1 formed by the first inclined portion 5c1 and the second inclined portion 5c2 of the connecting portion 5c, the acute angle θ2 formed by the first inclined portion 5c1 and the axial direction of the central tube 5a, and the existence ratio R of the rubber component contained in the gasket 5 is made different as shown in Table 1, thereby preparing alkaline dry batteries A1 to A14 of Examples 1 to 14 and alkaline dry batteries B1 to B15 of Comparative Examples 1 to 15.

[0097] 《Example 15》

[0098] The material of the gasket 5 was changed to a polypropylene resin in which a butadiene-styrene copolymer (SBR) was dispersed as a rubber component. In addition, the internal angle θ1, the acute angle θ2, and the abundance ratio R of the rubber component were changed as shown in Table 1. The alkaline dry battery A15 of Example 15 was produced in the same manner as in Example 1.

[0099] 《Example 16》

[0100] The material of the gasket 5 was changed to polypropylene resin in which styrene-isoprene copolymer (SIS) was dispersed as a rubber component. In addition, the internal angle θ1, the acute angle θ2 and the abundance ratio R of the rubber component were changed as shown in Table 1. The alkaline dry battery A16 of Example 16 was produced in the same manner as Example 1 otherwise.

[0101] The alkaline dry batteries A1 to A16 and B1 to B15 were subjected to the following evaluations (4) and (5).

[0102] (4) Evaluation 1: Constant current charging test

[0103] Prepare 10 batteries of the same structure. Place unused alkaline dry batteries in an environment of 25°C and charge them at a constant current of 200 mA for 1 hour. Batteries whose thin-walled parts of the gaskets break during charging and whose sealing components maintain the state of sealing the opening of the battery case are considered good products, and batteries whose thin-walled parts do not break and whose sealing components leave the opening of the battery case and open the opening are considered defective. Evaluate the proportion of batteries judged as defective among the 10 batteries.

[0104] (5) Evaluation 2: Over-discharge leakage test

[0105] Prepare 10 batteries of the same structure. Place unused alkaline dry batteries in an environment of 45°C, connect them to a 40Ω resistance load, and discharge them until the voltage between the terminals reaches 0.05V. Then, place them at 45°C for 3 months. Visually check whether there is leakage of alkaline electrolyte from the batteries after placement. Batteries without leakage are considered good, and batteries with leakage are considered defective. Evaluate the proportion of batteries judged to be defective among the 10 batteries.

[0106] Figure 4 Graph 1 shows the correspondence between the internal angle θ1 and the abundance ratio R of the rubber component and the evaluation results of the examples and comparative examples. Figure 4 In the figure, "·" is a diagram of the embodiment in which neither rupture nor leakage occurred, "+" is a diagram of the embodiment 15, "*" is a diagram of the embodiment 16, "△" is a diagram of the comparative example in which leakage occurred, and "×" is a diagram of the comparative example in which rupture occurred. Figure 4 It can be understood that within the range satisfying the equations (1) and (2), the liquid leakage property can be improved without hindering the operation of the explosion-proof valve.

[0107]

[0108] 《Examples 17 to 22, Comparative Example 16》

[0109] In order to evaluate the situation where leakage is more likely to occur, the filling amount of the positive electrode and the negative electrode was increased by 2% by mass. In addition, the internal angle θ1, the acute angle θ2 and the existence ratio R of the rubber component were changed as shown in Table 2. Otherwise, alkaline dry batteries A17 to 22 of Examples 17 to 22 were prepared in the same manner as in Example 1 and evaluated in the same manner.

[0110] The battery of Comparative Example 16 has the same configuration as that of Comparative Example 1, except that the filling amounts of the positive electrode and the negative electrode are increased by 2% by mass, respectively, compared with the battery of Comparative Example 1.

[0111]

[0112] As can be understood from Table 2, even when the positive and negative electrodes expand excessively during discharge and the gasket is compressed, the leakage resistance can be significantly improved without hindering the operation of the explosion-proof valve within the range satisfying equations (1) and (2).

[0113] Industrial Applicability

[0114] The alkaline dry battery of the present invention is useful as a power source for various electronic devices because the explosion-proof valve has excellent operating performance and liquid leakage is highly suppressed.

[0115] Description of Reference Numerals

[0116] 1 battery case, 2 positive electrode, 3 negative electrode, 4 separator, 5 gasket, 5a central cylinder, 5b peripheral portion, 5c connecting portion, 5c1 first inclined portion, 5c2 second inclined portion, 5d bent portion, 6 negative electrode collector, 7 negative terminal plate, 8 outer packaging label, 9 sealing assembly, 10 alkaline dry battery.

Claims

1. An alkaline dry battery, comprising: a battery case having an opening and a bottom on an opposite side of the opening, A power generation element housed in the battery case, and A sealing assembly for sealing the opening of the battery housing, The sealing assembly includes a terminal plate, a current collector joined to the terminal plate, and a gasket. The current collector has a cylindrical main body extending in the axial direction. The gasket includes a central tube portion through which the main body portion of the current collector passes, an outer peripheral portion sandwiched between the peripheral edge portion of the terminal plate and an opening end portion of the battery case facing the opening, and a connecting portion connecting the central tube portion and the outer peripheral portion. The connecting portion has: a curved portion that is convexly bulged toward the bottom of the battery case, A first inclined portion extending from the central cylindrical portion to the curved portion, a second inclined portion extending from the curved portion to the outer peripheral portion side, and The thin-walled portion is formed in a groove shape and is locally thin. The liner comprises a polypropylene resin, A rubber component is dispersed inside the gasket. The abundance ratio R (%) of the rubber component relative to the total of the polypropylene resin and the rubber component, and the internal angle θ1 (°) formed by the first inclined portion and the second inclined portion satisfy the following formula: 3≤R≤20 59×R+128≤θ1≤0.59×R+163.

2. The alkaline dry battery according to claim 1, wherein The axial direction of the central cylindrical portion forms an acute angle of 20° or more with the first inclined portion.

3. The alkaline dry battery according to claim 1 or 2, wherein: A width W of the connection portion in the radial direction of the central cylindrical portion and a height H of the connection portion in the axial direction of the central cylindrical portion satisfy W / H≥1.0.

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