Method for manufacturing alkaline dry cell and alkaline dry cell

Abstract

A method for manufacturing an alkaline dry battery includes first to third processes. In the first process, a hollow cylindrical first positive electrode pellet having a first end surface and a second end surface in an axial direction is prepared. In the second process, a hollow cylindrical positive electrode pellet group including the first positive electrode pellet is inserted into a case to obtain a positive electrode that is inscribed in the case. At this time, the first positive electrode pellet is disposed at a most opening side of the case so that the first end surface faces the opening side of the case. In the third process, an annular groove is provided at a side portion of the case. The first positive electrode pellet has a tapered portion whose outer diameter decreases from the second end surface toward the first end surface, and an inclination angle θ of the tapered portion with respect to an axis of the first positive electrode pellet in a cross section along the axial direction of the first positive electrode pellet is 0.26° or more and 0.87° or less. A distance h from the groove to the first end surface is 0.55 mm or more and 2.35 mm or less.

Description

Technical Field

[0001] This invention relates to a method for manufacturing alkaline dry cell batteries and alkaline dry cell batteries themselves. Background Technology

[0002] Alkaline dry cell batteries (alkaline manganese dry cell batteries) are widely used because of their large capacity and ability to extract a large current. The positive electrode of an alkaline dry cell is formed by stacking multiple hollow cylindrical granules containing manganese dioxide (Patent Documents 1 and 2, etc.). In the manufacturing method of an alkaline dry cell, multiple granules containing the positive electrode active material (manganese dioxide) are inserted into a casing and stacked to obtain a hollow cylindrical positive electrode connected to the casing. Then, an annular groove is formed in the region closer to the opening side than the positive electrode on the side of the casing.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2017-68905

[0006] Patent Document 2: Japanese Patent Application Publication No. 2019-61801 Summary of the Invention

[0007] Consider increasing the positive electrode filling height (axial height dimension) to achieve higher capacity. However, if the positive electrode filling height is increased, the distance between the groove and the end face of the positive electrode housing opening side becomes smaller. The impact during groove formation is more easily transmitted to the end of the positive electrode housing opening side, which may cause cracking at the end of the positive electrode housing opening side.

[0008] One aspect of the present invention relates to a method for manufacturing an alkaline dry cell battery, comprising: a first step of preparing a hollow cylindrical first positive electrode granule, the first positive electrode granule having an axial first end face and a second end face opposite to the first end face; a second step of inserting a group of hollow cylindrical positive electrode granules containing the first positive electrode granule into a bottomed cylindrical shell to obtain a hollow cylindrical positive electrode inlaid within the shell; and a third step of providing an annular groove in a region on the side of the shell closer to the opening side than the positive electrode.

[0009] The first positive electrode granule has a tapered portion whose outer diameter decreases from the second end face to the first end face, and in a cross section along the axial direction of the first positive electrode granule, the inclination angle θ of the tapered portion relative to the axis of the first positive electrode granule is 0.26° or more and 0.87° or less. In the second step, the first positive electrode granule is disposed on the side closest to the opening of the housing such that the first end face faces the opening side of the housing, and the distance h between the groove and the first end face is 0.55 mm or more and 2.35 mm or less.

[0010] Another aspect of the present invention relates to an alkaline dry cell battery comprising: a bottomed cylindrical housing having a groove; a hollow cylindrical positive electrode connected to a region of the housing further down than the groove; a negative electrode disposed within the hollow portion of the positive electrode; a separator disposed between the positive and negative electrodes; an electrolyte; and a sealing unit disposed on a stepped portion of the housing provided through the groove and sealing the opening of the housing.

[0011] The distance h between the groove and the end face of the positive electrode on the groove side is 0.55 mm or more and 2.35 mm or less. When the alkaline dry cell is disassembled to expose the positive electrode from the casing to the outside, the positive electrode has a tapered portion whose outer diameter decreases from the bottom side of the casing to the groove side. Furthermore, in a cross section along the axial direction of the positive electrode, the inclination angle θ of the tapered portion relative to the axis of the positive electrode is 0.26° or more and 0.87° or less.

[0012] According to the present invention, the filling volume of the positive electrode can be increased, and the cracking of the positive electrode during the formation of the groove in the casing can be suppressed. Attached Figure Description

[0013] Figure 1 This is a schematic side view showing an example of the first positive electrode granules obtained by the first step of the manufacturing method of an alkaline dry cell according to an embodiment of the present invention.

[0014] Figure 2 This is a schematic side view showing another example of the first positive electrode granules obtained by the first step of the manufacturing method of an alkaline dry cell according to an embodiment of the present invention.

[0015] Figure 3 This is a schematic side view showing an example of a group of positive electrode particles inserted into the casing in the second step of a method for manufacturing an alkaline dry cell according to an embodiment of the present invention.

[0016] Figure 4 This is a schematic side view showing another example of a group of positive electrode particles inserted into the casing in the second step of a method for manufacturing an alkaline dry cell according to an embodiment of the present invention.

[0017] Figure 5 This is a schematic side view showing another example of a group of positive electrode particles inserted into the casing in the second step of a method for manufacturing an alkaline dry cell according to an embodiment of the present invention.

[0018] Figure 6This is a cross-sectional view of the main part showing the state in which an annular groove is provided on the side of the casing inside the positive electrode in the third step of the manufacturing method of an alkaline dry cell according to an embodiment of the present invention.

[0019] Figure 7 The front view is a cross-section of half of the alkaline dry cell according to one embodiment of the present invention. Detailed Implementation

[0020] [Manufacturing method of alkaline dry cell batteries]

[0021] The method for manufacturing an alkaline dry cell according to embodiments of the present invention includes the following steps 1 to 3. The first step is a step of preparing a first positive electrode granule. The second step is a step of inserting a hollow cylindrical positive electrode granule group containing the first positive electrode granule into a bottomed cylindrical shell to obtain a hollow cylindrical positive electrode in contact with the shell. The third step is a step of providing an annular groove in a region closer to the opening side than the positive electrode on the side of the shell. The first positive electrode granule is a hollow cylindrical shape, having a first end face axially and a second end face opposite to the first end face.

[0022] The first positive electrode granule has a tapered portion whose outer diameter decreases from the second end face to the first end face. In a cross-section along the axial direction of the first positive electrode granule (viewed from the side), the inclination angle (hereinafter also referred to as "inclination angle θ") of the tapered portion relative to the axis of the first positive electrode granule is 0.26° or more and 0.87° or less. In the second process, the first positive electrode granule is positioned on the opening side of the housing such that the first end face faces the opening side of the housing. The distance (hereinafter also referred to as "distance h") between the groove (including the imaginary surface containing the position where the depth of the annular groove is the greatest) and the first end face is 0.55 mm or more and 2.35 mm or less. In other words, the distance h can be the height of the deepest part of the groove in the axial direction of the first positive electrode granule from the first end face.

[0023] When the tilt angle θ and distance h are within the aforementioned ranges, the filling height (axial height dimension) of the positive electrode can be increased to improve capacity and suppress the occurrence of positive electrode breakage during groove formation. Furthermore, the aforementioned breakage refers to the phenomenon where cracks form from the periphery of the end face of the positive electrode's shell opening side (the first end face of the first granule) inwards due to the impact during groove formation in the shell during the third process. Because of this breakage, the conductive path is interrupted, resulting in portions that do not contribute to the discharge reaction, potentially reducing discharge performance.

[0024] In the second process, the first positive electrode granules are pressed into the shell, adhering tightly to the inner surface of the shell. At this time, since the tilt angle θ is relatively small, less than 0.87°, the first positive electrode granules are slightly deformed due to insertion into the shell, and swell due to absorption by the electrolyte. Therefore, the conical portion is also in a state of being tightly adhering to or in contact with the inner surface of the shell to some extent. When the tilt angle θ is greater than 0.26°, the degree of adhesion between the conical portion (the end of the positive electrode shell opening side) and the inner surface of the shell is moderately reduced, which can reduce the impact transmitted to the conical portion (the end of the positive electrode shell opening side) during tank formation. Therefore, even if the filling height of the positive electrode is increased and the distance h is reduced to less than 2.35 mm, the occurrence of positive electrode breakage can be suppressed. However, if the distance h becomes less than 0.55 mm, even if the tilt angle θ is greater than 0.26°, breakage may occur in the positive electrode during tank formation.

[0025] When the tilt angle θ is less than 0.26°, if the distance h decreases to less than 2.35 mm, the probability of cracking at the positive electrode during trench formation increases significantly. On the other hand, when the tilt angle θ exceeds 0.87° and / or the distance h exceeds 2.35 mm, the filling volume of the positive electrode may become smaller.

[0026] From the viewpoint of suppressing cathode breakage and facilitating an increase in cathode filling volume, a tilt angle θ of 0.26° or more and 0.52° or less is preferred. Similarly, a distance h of 0.55 mm or more and 1.35 mm or less is preferred.

[0027] The value of subtracting the inner diameter of the casing from the maximum outer diameter of the first positive electrode granule is preferably 0 mm or more and 0.06 mm or less. Furthermore, the maximum outer diameter of the first positive electrode granule refers to the maximum outer diameter of the first granule before it is inserted into the casing. For example, when the first positive electrode granule is... Figure 1 or Figure 2 In the case of the first particle shown, Figure 1 as well as Figure 2 The outer diameter D2 corresponds to the maximum outer diameter. Furthermore, the inner diameter of the casing refers to the size of the inner diameter of the casing before the positive electrode particles are inserted into it. These values ​​can also be determined, for example, by using a laser to cut the casing of the finished battery, separating the first positive electrode particles from the casing.

[0028] When the difference between the maximum outer diameter of the first positive electrode granule and the inner diameter of the shell is 0 mm or more, good adhesion between the positive electrode and the shell is easily achieved. When the difference between the maximum outer diameter of the first positive electrode granule and the inner diameter of the shell is 0.06 mm or less, the occurrence of cracks in the positive electrode can be suppressed. Here, a crack refers to the phenomenon of a thin, circumferential peeling off the periphery of the end face of the opening side of the positive electrode shell (the first end face of the first positive electrode granule). The crack itself has almost no effect on the discharge performance, but it may become an important factor in the occurrence of positive electrode breakage in subsequent processes.

[0029] From the viewpoint of suppressing cathode breakage, the tapered portion does not need to be provided on the entire side surface from the first end face to the second end face of the first cathode pellet. The tapered portion can also be provided in the side surface region from the first end face to the midway between the first and second end faces of the first cathode pellet. Preferably, the tapered portion is provided along the entire circumference of the side surface of the first cathode pellet, and more preferably, it is provided on the entire side surface from the first end face to the second end face of the first cathode pellet.

[0030] In a cross-section along the axial direction of the first positive electrode granule (viewed from the side of the first positive electrode granule), the profile of the tapered portion can be straight or curved, such as a slightly expanded arc. In the case of a curve, the inclination angle θ refers to the angle formed by the line segment (chord) connecting the two ends of the curve (arc) and the axis of the first positive electrode granule.

[0031] (Step 1)

[0032] The first positive electrode granules can be manufactured, for example, by pressing a positive electrode mixture containing a positive electrode active material, a conductive agent, and an electrolyte into a desired shape. Alternatively, the positive electrode mixture can be temporarily set into flakes or granules, graded as needed, and then pressed into shape. The density of manganese dioxide in the first positive electrode granules can be adjusted by regulating the pressing pressure.

[0033] The positive electrode active material includes manganese dioxide. Electrolytic manganese dioxide is preferred. The manganese dioxide is used in powder form. From the viewpoint of easily ensuring the filling quality of the positive electrode and the diffusion of the electrolyte within the positive electrode, the average particle size (D50) of the manganese dioxide is, for example, 20 μm or more and 60 μm or less. From the viewpoint of formability and suppression of positive electrode expansion, the BET specific surface area of ​​the manganese dioxide can also be, for example, 15 m². 2 / g or more and 50m 2 The range is below / g. The average density of manganese dioxide in the first cathode granule is, for example, 2.78 g / cm³. 3 Above and 3.08 g / cm 3 the following.

[0034] Furthermore, in this specification, the term "average particle size" (D50) refers to the median diameter in the particle size distribution on a volume basis. The average particle size is determined, for example, using laser diffraction and / or a scattering-type particle size distribution measuring device. Additionally, the term "BET specific surface area" is obtained by measuring and calculating the surface area using the theoretical formula for multilayer adsorption, namely the BET formula. The BET specific surface area can be measured, for example, using a specific surface area measuring device based on nitrogen adsorption.

[0035] As a conductive agent, conductive carbon materials such as graphite are used, for example, in addition to carbon black such as acetylene black. Natural graphite, artificial graphite, etc., can be used as graphite. The conductive agent can be in fibrous form, but is preferably in powder form. The average particle size (D50) of the conductive agent can be selected, for example, from a range of 5 nm or more and 50 μm or less. When the conductive agent is carbon black, the average particle size (D50) of the conductive agent is preferably 5 nm or more and 40 nm or less; when the conductive agent is graphite, it is preferably 3 μm or more and 50 μm or less. The amount of the conductive agent in the positive electrode mixture relative to 100 parts by mass of manganese dioxide is, for example, 3 parts by mass or more and 10 parts by mass or less, preferably 4 parts by mass or more and 8 parts by mass or less.

[0036] For the electrolyte, for example, an alkaline aqueous solution containing potassium hydroxide is used. The concentration of potassium hydroxide in the electrolyte is, for example, 30% by mass or more and 50% by mass or less. The electrolyte may also further contain zinc oxide. The concentration of zinc oxide in the electrolyte is, for example, 1% by mass or more and 5% by mass or less. The amount of electrolyte in the positive electrode mixture relative to 100 parts by mass of manganese dioxide is, for example, 4 parts by mass or more and 15 parts by mass or less.

[0037] The positive electrode mixture may also contain additives. For example, in addition to polyacrylic acid, polyethylene or polytetrafluoroethylene can be used as additives. The amount of additives in the positive electrode mixture relative to 100 parts by weight of manganese dioxide is, for example, 0.1 parts by weight or more and 1.0 parts by weight or less.

[0038] The following description refers to the accompanying drawings. In each drawing, the dimensions of the various structural components of the battery are shown relative to the figures to clarify their shapes or features. These dimensions are not necessarily expressed to the same scale. Figure 1 This is a schematic side view showing an example of the first positive electrode granules obtained by the first step in the manufacturing method of an alkaline dry cell according to an embodiment of the present invention.

[0039] Figure 1The first granule 100 shown is a hollow cylindrical shape, having an axial first end face E1 and a second end face E2 opposite to the first end face E1. The first granule 100 has a tapered portion T whose outer diameter decreases from D2 to D1 from the second end face E2 towards the first end face E1. Furthermore, in a cross-section along the axial direction of the first granule 100 (from...) Figure 1 (Viewed from the side of the first granule 100), the angle of inclination θ of the tapered portion T relative to the axis of the first granule 100 is 0.26° or more and 0.87° or less. In the first granule 100, the tapered portion T is provided from the second end face E2 to the first end face E1 (the entire side of the first granule 100).

[0040] The size of the battery is not particularly limited and can be any size, but for example, if it is a single-triangular battery, the height H of the first granule 100 (conical portion T) is, for example, 10.60 mm or more and 22.10 mm or less. Furthermore, the outer diameter D2 of the first granule 100 is, for example, 13.60 mm or more and 13.76 mm or less. Additionally, in the first granule 100, the ratio of outer diameter D2 to outer diameter D1, D2 / D1, is, for example, 1.01 or more and 1.05 or less.

[0041] In the case of a single tetrahedral cell, the height H of the first granule 100 (conical portion T) is, for example, 8.91 mm or more and 18.53 mm or less. Furthermore, the outer diameter D2 of the first granule 100 is, for example, 10.10 mm or more and 10.25 mm or less. Additionally, in the first granule 100, the ratio of outer diameter D2 to outer diameter D1, D2 / D1, is, for example, 1.01 or more and 1.03 or less.

[0042] In the case of a single-shaped cell, the height H of the first granule 100 (conical portion T) is, for example, 24.35 mm or more and 49.40 mm or less. Furthermore, the outer diameter D2 of the first granule 100 is, for example, 32.00 mm or more and 32.36 mm or less. Additionally, in the first granule 100, the ratio of outer diameter D2 to outer diameter D1, D2 / D1, is, for example, approximately 1.01.

[0043] In the case of a single-cell diode, the height H of the first granule 100 (conical portion T) is, for example, 19.55 mm or more and 39.80 mm or less. Furthermore, the outer diameter D2 of the first granule 100 is, for example, 24.40 mm or more and 24.66 mm or less. Additionally, in the first granule 100, the ratio of outer diameter D2 to outer diameter D1, D2 / D1, is, for example, approximately 1.01.

[0044] Figure 2 This is a schematic side view showing another example of the first positive electrode granules obtained by the first step in the manufacturing method of an alkaline dry cell according to an embodiment of the present invention. Additionally, in Figure 2In, the description of the structure repeated for the first pellet 100 corresponding to Figure 1 is omitted.

[0045] In Figure 2 In the first pellet 200 shown, a tapered portion T is provided in a part on the side of the first end face E1 of the first pellet 200 (a side region from the first end face to the middle between the first end face and the second end face). Figure 2 The height H, outer diameter D2, and D1 / D2 of the tapered portion of the first pellet 200 of Figure 1 can also be within the ranges exemplified for the height H, outer diameter D2, and D1 / D2 of the tapered portion of the first pellet 100 of

[0046] (Second process)

[0047] In the second process, a hollow cylindrical positive electrode pellet group containing the first positive electrode pellet is inserted into a bottomed cylindrical housing to obtain a hollow cylindrical positive electrode inscribed in the housing. For the housing, a nickel-plated steel sheet is used, for example. In order to improve the close contact between the positive electrode and the housing, the inner surface of the housing can also be covered with a carbon film.

[0048] Other positive electrode pellets other than the first positive electrode pellet in the positive electrode pellet group (hereinafter, simply referred to as other positive electrode pellets) can also be produced by pressure-forming the above positive electrode mixture in the same manner as the first positive electrode pellet. The shape and size of the other positive electrode pellets can be different from those of the first positive electrode pellet. From the viewpoint of productivity, it is preferable to have substantially the same shape and size as the first positive electrode pellet. The orientation of inserting the other positive electrode pellets into the housing is not particularly limited. From the viewpoint of productivity, when each positive electrode pellet has substantially the same shape and size, it is preferable that the first end faces of each positive electrode pellet are respectively arranged facing the opening side of the housing and the positive electrode pellets are stacked. The number of positive electrode pellets included in the positive electrode pellet group is, for example, 2 or more and 4 or less. When each positive electrode pellet has substantially the same shape and size, the error in the length dimension (for example, the height dimension) of the positive electrode pellet is, for example, about 3% or less. The above-mentioned error refers to the ratio of the difference (absolute value) between the maximum value farthest from the average value and the average value to the average value with respect to the length dimension etc. of each positive electrode pellet.

[0049] Here, Figures 3-5 is a schematic side view showing three examples of a positive electrode pellet group (stacked body) constituting a positive electrode. In Figures 3-5 a tapered portion is shown. Therefore, for the sake of convenience, the state before the stacked body is inserted into the housing is shown.

[0050] Figure 3 The positive electrode 2 shown is composed of a stacked body of a hollow cylindrical first pellet 2a and a second pellet 2b.

[0051] The first granule 2a has a first end face E1 along the axial direction and a second end face E2 on the side opposite to the first end face E1. The first granule 2a has a tapered portion T whose outer diameter decreases from the second end face E2 towards the first end face E1. Furthermore, in a cross-section along the axial direction of the first granule 2a (from... Figure 3 (As shown in the side view of the first granule 2a), the angle of inclination θ of the tapered portion T relative to the axis of the first granule 2a is 0.26° or more and 0.87° or less. In the first granule 2a, the tapered portion T is provided from the second end face E2 to the first end face E1 (the entire side of the first granule 2a). The second granule 2b has almost the same shape and size as the first granule 2a.

[0052] Each of the granules 2a and 2b is inserted into the shell such that its first end face E1 faces the shell opening. The first granule 2a and the second granule 2b are arranged sequentially from the shell opening side. That is, on the shell's opening side, the first granule 2a is arranged with its first end face E1 facing the shell opening side.

[0053] exist Figure 3 In this process, the second pellet has almost the same shape and size as the first pellet, but is not limited to this; its shape and size may also differ from the first pellet. The second pellet may also lack the tapered portion T. Furthermore, in... Figure 3 In this configuration, the second granule is configured such that the first end face E1 faces the opening side of the housing, but it can also be configured such that the second end face E2 faces the opening side of the housing.

[0054] exist Figure 3 In this context, it refers to the situation where two particles with nearly identical shapes and sizes are stacked to form a positive electrode, but the positive electrode is not limited to this. It can also be like... Figure 4 As shown, three granules (granules 12a to 12c) having almost identical shapes and sizes are stacked to form the positive electrode 12. Furthermore, as... Figure 5 As shown, four granules (granule 1 22a to granule 4 22d) with almost identical shapes and sizes can also be stacked to form the positive electrode 22.

[0055] (Step 3)

[0056] In the third step, for example, the housing is rotated around an axis and the grooving roller is pressed against a predetermined position on the side of the housing (near the open end), and this position is lifted towards the axis. This creates an annular groove in a region closer to the open side than the positive pole of the housing side. The depth of the groove can be controlled by adjusting the shape of the grooving roller, the load when lifting towards the axis, and the lifting height.

[0057] Here, Figure 6This is a cross-sectional view of the main part showing the state in which an annular groove is provided on the side of the casing inside the positive electrode in the third step of the manufacturing method of an alkaline dry cell according to an embodiment of the present invention.

[0058] A hollow cylindrical positive electrode 2 is internally connected to a housing 1. On the positive electrode 2, at the opening side of the housing 1, a first granule 2a with a conical portion T is positioned such that its first end face E1 faces the opening side of the housing 1. The inclination angle θ of the conical portion T is 0.26° or more and 0.87° or less. An annular groove 21 is provided in the region of the side portion 1a of the housing 1 that is closer to the opening side than the positive electrode 2. The groove 21 (an imaginary surface S21 containing the deepest part of the annular groove 21) is separated from the end face 11 (the first end face E1 of the first granule 2a) of the housing 1 on the opening side of the positive electrode 2 by a distance h of 0.55 mm or more and 2.35 mm or less. In this case, the impact transmitted to the opening side end of the housing 1 of the positive electrode 2 during the formation of the groove 21 can be reduced, and the breakage of the positive electrode 2 caused by the formation of the groove 21 can be suppressed.

[0059] The depth d of the groove 21 (deepest part) is preferably 0.3 mm or more and 2.2 mm or less. When the groove depth d is 0.3 mm or more, the groove forms a sufficient step portion, making it easy to mount the sealing unit on the step portion, thus improving the reliability of the battery's sealing performance. When the groove depth d is 2.2 mm or less, the occurrence of cracks in the positive electrode can be suppressed. The depth d of the groove 21 can be obtained by measuring the outer diameter Da of the portion other than the groove 21 and the outer diameter Db of the deepest part of the groove 21 for the side portion 1a of the casing, and then using the formula (Da-Db) / 2. In the case of the battery (finished product), the outer diameter Da and outer diameter Db can be measured using the side portion of the casing when viewing the battery from the side.

[0060] exist Figure 6 In the middle, the shell 1 contains Figure 3 The positive electrode is 2, but the positive electrode is not limited to this. For example, it could also be... Figure 4 The positive electrode 12 or Figure 5 The positive electrode 22.

[0061] (Steps 4 and 5)

[0062] Furthermore, the above-described manufacturing method may also include: a fourth step of configuring a negative electrode in the hollow portion of the positive electrode through a separator and injecting electrolyte into the casing; and a step portion provided in the groove passing through the casing (through... Figure 6 The fifth step involves configuring a sealing unit on the stepped portion 31 of the groove 21 and sealing the opening of the housing through the sealing unit.

[0063] [Alkaline dry cell batteries]

[0064] An embodiment of the alkaline dry cell according to the present invention includes: a bottomed cylindrical casing with a groove; a hollow cylindrical positive electrode connected to the casing in a region further to the bottom than the groove; a negative electrode disposed within the hollow portion of the positive electrode; a separator disposed between the positive and negative electrodes; and an electrolyte. Furthermore, the alkaline dry cell includes a sealing unit disposed on a stepped portion provided through the groove of the casing and sealing the opening of the casing. The distance h between the groove and the end face of the positive electrode on the groove side (the opening side of the casing) is 0.55 mm or more and 2.35 mm or less.

[0065] When the alkaline dry cell is disassembled to expose the positive electrode from the casing (assuming the positive electrode is not internally connected to the casing), the tapered portion (tilt angle θ) provided on the outer peripheral surface of the positive electrode (pile) almost returns to its state before insertion into the casing. That is, the positive electrode removed from the casing has a tapered portion whose outer diameter decreases from the bottom side of the casing to the slot side, and in a cross section along the axial direction of the positive electrode, the tilt angle θ of the tapered portion relative to the axis of the positive electrode is 0.26° or more and 0.87° or less.

[0066] The negative electrode is disposed within the hollow portion of the positive electrode granules. The negative electrode has a gel-like morphology. The negative electrode typically contains: zinc or zinc alloy powder as the negative electrode active material, an electrolyte, and a gelling agent. An electrolyte that incorporates the positive electrode granules can be used.

[0067] From the viewpoint of corrosion resistance, the zinc alloy preferably contains at least one selected from the group containing indium, bismuth, and aluminum. The negative electrode active material is typically used in powder form. From the viewpoint of the filling properties of the negative electrode and the diffusion properties of the alkaline electrolyte within the negative electrode, the average particle size (D50) of the negative electrode active material powder is, for example, 80 μm or more and 200 μm or less, preferably 100 μm or more and 150 μm or less. The content of zinc or zinc alloy powder in the negative electrode is, for example, 170 parts by mass or more and 220 parts by mass per 100 parts by mass of electrolyte.

[0068] As a gelling agent, known gelling agents used in the field of alkaline dry batteries are not particularly limited to use; for example, thickeners and / or water-absorbing polymers can be used. Examples of such gelling agents include polyacrylic acid and sodium polyacrylate. The content of the gelling agent in the negative electrode is, for example, 0.5 parts by mass and 2 parts by mass per 100 parts by mass of the negative electrode active material.

[0069] For example, nonwoven fabrics or microporous membranes can be used as the separator. Examples of materials for the separator include cellulose and polyvinyl alcohol. Nonwoven fabrics can be made primarily of fibers from these materials. Microporous membranes can be made of materials such as celluloid. The thickness of the separator is, for example, 80 μm or more and 300 μm or less. The separator can also be constructed by overlapping multiple sheets (such as nonwoven fabrics) to achieve the thickness within the aforementioned range.

[0070] The alkaline dry cell battery according to the present invention will now be described in detail with reference to the accompanying drawings. However, the present invention is not limited to the following embodiments. Furthermore, appropriate modifications can be made without departing from the scope of achieving the effects of the present invention. Furthermore, combinations with other embodiments are also possible.

[0071] Figure 7 The front view is a cross-section of half of the alkaline dry cell according to one embodiment of the present invention.

[0072] like Figure 7 As shown, an alkaline dry cell includes: a hollow cylindrical positive electrode 2, a negative electrode 3 disposed within the hollow portion of the positive electrode 2, a separator 4 disposed between them, and an electrolyte (not shown), all housed within a bottomed cylindrical casing 1 having a side 1a and a bottom 1b. The bottom 1b of the casing 1 also serves as the positive terminal. The positive electrode 2 is filled within the casing 1, and the gel-like negative electrode 3 is filled within the hollow portion of the positive electrode 2, separated by the separator 4.

[0073] The positive electrode 2 contains manganese dioxide and usually also contains a conductive agent. The negative electrode 3, in addition to a zinc-containing negative electrode active material, usually contains an alkaline electrolyte and a gelling agent. The separator 4 is a bottomed cylindrical shape, consisting of a cylindrical separator 4a and a backing paper 4b. The separator 4a is disposed along the inner surface of the hollow portion of the positive electrode 2, separating the positive electrode 2 from the negative electrode 3. Therefore, the separator disposed between the positive and negative electrodes refers to the cylindrical separator 4a. The backing paper 4b is disposed at the bottom of the hollow portion of the positive electrode 2, separating the negative electrode 3 from the housing 1.

[0074] The opening of the casing 1 is sealed by the sealing unit 9. The sealing unit 9 includes: a gasket 5, a negative terminal plate 7 that also serves as the negative terminal, and a negative current collector 6. The gasket 5 has an annular thin-walled portion 5a. If the internal pressure of the battery exceeds a specified value, the thin-walled portion 5a breaks, and gas is released to the outside of the battery.

[0075] A negative current collector 6 is inserted into the negative electrode 3. The negative current collector 6 is made of an alloy containing copper and zinc, such as brass. The negative current collector 6 may also be plated with zinc or other plating processes as needed. The negative current collector 6 has a nail-like shape including a head and a body. The body is inserted into a through hole in the central cylindrical part of the gasket 5, and the head of the negative current collector 6 is welded to the flat part in the center of the negative terminal plate 7.

[0076] An annular groove 21 is provided in the area of ​​the housing side 1a closer to the opening side than the positive electrode 2. The opening end of the housing 1 (the area of ​​the housing side 1a closer to the opening side than the groove 21) is riveted to the flange of the peripheral portion of the negative electrode plate 7 via the outer peripheral end of the gasket 5. An external label 8 is covered on the outer surface of the housing 1. The distance h between the end face 11 of the positive electrode 2 on the groove 21 side (the first end face E1 of the first granule 2a) and the groove 21 (the imaginary face S21 including the deepest part of the annular groove 21) is 0.55 mm or more and 2.35 mm or less.

[0077] Positive electrode 2 is composed of Figure 3 The assembly shown consists of a first granule 2a and a second granule 2b. Each granule 2a and 2b is pressed into the housing 1 such that its first end face E1 faces the opening side of the housing 1 and contacts the inner surface of the housing 1. When the assembly is removed from the housing 1, the inclination angle θ of the conical portion T of the first granule 2a is 0.26° or more and 0.87° or less.

[0078] exist Figure 7 In this design, the positive electrode 2 is housed within the casing 1, but the positive electrode is not limited to this. For example, it could also be positive electrode 12 or positive electrode 22.

[0079] exist Figure 7 In this design, the separator is composed of a cylindrical separator 4a and a backing paper 4b, but is not limited to this. A single, bottomed cylindrical component can also be used as the separator, and separators of known shapes used in the field of alkaline dry batteries can be employed.

[0080] [Example]

[0081] The present invention will now be described in detail based on embodiments and comparative examples, but the present invention is not limited to the following embodiments.

[0082] Examples 1-18 and Comparative Examples 1-14

[0083] (Step 1)

[0084] Electrolytic manganese dioxide powder (manganese dioxide purity: 93%, average particle size D50: 40 μm, BET specific surface area: 26 m² / g) as the positive electrode active material, graphite powder as the conductive agent, and polytetrafluoroethylene (PTFE) as the additive were mixed. Electrolyte was added to the mixture, and after thorough stirring, it was compressed into thin sheets, which were further pulverized into granules to obtain the positive electrode mixture. The mass ratio of each component was set as electrolytic manganese dioxide powder: graphite powder: electrolyte = 95:5:2. The additive was used at a ratio of 0.2% by mass relative to the electrolytic manganese dioxide. An alkaline aqueous solution containing potassium hydroxide (35% by mass) and zinc oxide (2% by mass) was used as the electrolyte.

[0085] The positive electrode mixture is manufactured by pressing and shaping it using a metal mold. Figure 3 The two granules shown are granule 1 (2a) and granule 2 (2b). The density of manganese dioxide is set to 2.80 g / cm³ by adjusting the pressure during the pressing process. 3 The manganese dioxide density of these granules is the value at the time of granule production. The manganese dioxide density of the produced granules is obtained by dividing the mass of manganese dioxide calculated from the raw material composition by the volume calculated from the granule size. For each granule, the inclination angle θ of the conical portion T is set to the values ​​shown in Tables 1 to 3, the outer diameter D2 (maximum outer diameter) of the second end face E2 is set to 13.70 mm, the height H of the granule (conical portion) is set to 21.80 mm, and the inner diameter (diameter of the hollow portion) is set to 8.90 mm.

[0086] (Step 2)

[0087] Next, the two granules obtained above ( Figure 3 The stack shown is configured with its first end face E1 facing the opening side of the shell and inserted into the shell (inner diameter: 13.70 mm). This creates a positive electrode connected to the shell. For the shell, a component with a carbon film approximately 10 μm thick can be formed by coating the inner surface of a bottomed cylindrical shell (body thickness: 0.15 mm) made of nickel-plated steel sheet with a graphite product (Bani-Hite) manufactured by Nippon Graphite Co., Ltd.

[0088] (Step 3)

[0089] An annular groove is provided on the side of the casing, closer to the opening side than the positive electrode. The position of the groove is adjusted so that the distance h from the opening side end face of the positive electrode casing (the first end face of the first granule) is the value shown in Tables 1 to 3. Furthermore, the groove depth d is set to the value shown in Tables 1 to 3.

[0090] The following evaluation was conducted on the positive electrodes connected to the housing with grooves obtained in Examples 1-18 and Comparative Examples 1-14.

[0091] [Evaluation: Cathode breakage rate]

[0092] Ten positive electrodes were fabricated and connected to a casing with grooves. The presence of cracks (crazing from the periphery of the end face of the positive electrode with an opening on the casing) was visually checked. The number of cracked positive electrodes among the ten was counted, and the cracking rate of the positive electrodes was calculated. The evaluation results are shown in Tables 1 to 3.

[0093] [Table 1]

[0094]

[0095] [Table 2]

[0096]

[0097] [Table 3]

[0098]

[0099] In Examples 1-18, the breakage rate of the positive electrode was 0%. In Comparative Examples 1-12, which used positive electrode granules with a conical inclination angle of 0.20°, breakage was observed in the positive electrode. In Comparative Examples 13 and 14, where the conical inclination angle was 0.26° and the distance h between the groove and the first end face was 0.35 mm, breakage was observed in the positive electrode.

[0100] Example 19

[0101] In the first process, three granules with almost identical shapes and sizes are produced. Figure 4 The first granule 12a to the third granule 12c are shown. For each granule, the inclination angle θ of the conical part is set to 0.26°, the outer diameter D2 (maximum outer diameter) of the second end face E2 is set to 13.70 mm, and the height H of the granule (conical part) is set to 14.53 mm.

[0102] In the second step, the three granules obtained above are prepared. Figure 4 The stack shown is inserted into the housing with the first end face E1 facing the opening side of the housing. In this way, a positive electrode is obtained that is connected to the housing.

[0103] In addition to the above, a positive electrode connected to a housing with a groove was fabricated and evaluated using the same method as in Example 1.

[0104] Example 20

[0105] In the first process, four granules with almost identical shapes and sizes are produced. Figure 5 The first granule 22a to the fourth granule 22d are shown. For each granule, the inclination angle θ of the conical part is set to 0.26°, the outer diameter D2 (maximum outer diameter) of the second end face E2 is set to 13.70 mm, and the height H of the granule (conical part) is set to 10.90 mm.

[0106] In the second step, the four granules obtained above are prepared. Figure 5 The stack shown is inserted into the housing with the first end face E1 facing the opening side of the housing. In this way, a positive electrode is obtained that is connected to the housing.

[0107] In addition to the above, a positive electrode was fabricated and evaluated using the same method as in Example 1, which was connected to the housing with the groove.

[0108] Example 21

[0109] In the first process, five granules (granules 1 through 5) that are almost identical in shape and size are produced. Each granule is... Figure 1 The shape shown has the following characteristics: the inclination angle θ of the conical part T is set to 0.26°, the outer diameter D2 (maximum outer diameter) of the second end face E2 is 13.70 mm, and the height H of the granules (conical part) is set to 8.70 mm.

[0110] In the second step, the five granules (accumulated bodies) obtained above are arranged such that the first end face E1 faces the opening side of the shell and are inserted into the shell. In this way, a positive electrode is obtained that is connected to the shell.

[0111] Table 4 shows the evaluation results of Examples 19-21.

[0112] [Table 4]

[0113]

[0114] In Examples 19 and 20, similar to Example 1, the rate of breakage of the positive electrode was 0%.

[0115] Examples 22-24

[0116] In the first step, with respect to the first and second granules, the tilt angle θ remains unchanged, while the outer diameter D1 of the first end face E1 and the outer diameter D2 of the second end face E2 are changed so that the value obtained by subtracting the inner diameter of the shell from the maximum outer diameter of each granule (outer diameter D2 of the second end face E2) is the value shown in Table 5. Apart from the above, a positive electrode connected inside the shell with the groove is manufactured using the same method as in Example 1.

[0117] Examples 25-27

[0118] Except that the depth d of the groove set in the housing in the third step is set to the value shown in Table 6, a positive electrode connected inside the housing with the groove is made by the same method as in Example 1.

[0119] For the positive electrodes connected inside the housing with grooves obtained in Examples 22-27, the breakage rate of the aforementioned positive electrodes was determined. Furthermore, the following evaluations were also conducted for Examples 1, 22-27.

[0120] [Evaluation: Crack incidence rate in the positive electrode]

[0121] Ten positive electrodes were fabricated inside the grooved casing. X-ray transmission imaging was used to confirm the presence or absence of cracks in the positive electrodes (a phenomenon of thin, circumferential peeling at the periphery of the end face of the positive electrode on the open side of the casing). The number of positive electrodes with cracks among the ten was counted, and the crack incidence rate of the positive electrodes was calculated.

[0122] The evaluation results are shown in Tables 5 and 6.

[0123] [Table 5]

[0124]

[0125] [Table 6]

[0126]

[0127] In Examples 22-27, the positive electrode fracture rate was 0%, similar to that in Example 1. Specifically, the positive electrode fracture rate was also 0% in Examples 1, 22-23, and 25-26.

[0128] Industrial availability

[0129] The alkaline dry cell batteries described in the embodiments of the present invention are advantageous for increasing capacity and improving reliability, and therefore can be appropriately used as power sources for electronic devices such as portable devices.

[0130] -Symbol Explanation-

[0131] 1: Shell, 1a: Side, 1b: Bottom, 2, 12, 22: Positive electrode, 2a, 12a, 22a, 100, 200: First granule, 2b, 12b, 22b: Second granule, 12c, 22c: Third granule, 22d: Fourth granule, 3: Negative electrode, 4: Isolator, 4a: Cylindrical isolator, 4b: Backing paper, 5: Gasket, 6: Negative electrode current collector, 7: Negative terminal plate, 8: External label, 9: Sealing unit, 11: End face of the positive electrode on the groove side, 21: Groove, 31: Stepped portion, E1: First end face, E2: Second end face, S21: Imaginary surface containing the deepest part of the annular groove.

Claims

1. A method for manufacturing an alkaline dry cell battery, comprising: The first step involves preparing a hollow cylindrical first positive electrode granule, which has an axial first end face and a second end face on the opposite side of the first end face. In the second step, a hollow cylindrical group of positive electrode granules containing the first positive electrode granules is inserted into a bottomed cylindrical shell to obtain a hollow cylindrical positive electrode connected to the shell; and In the third step, an annular groove is formed in the region on the side of the housing that is closer to the opening than the positive electrode. The first positive electrode granule has a tapered portion whose outer diameter decreases from the second end face to the first end face, and in a cross section along the axial direction of the first positive electrode granule, the inclination angle θ of the tapered portion relative to the axis of the first positive electrode granule is 0.26° or more and 0.87° or less. In the second step, the first positive electrode granules are positioned on the side of the housing closest to the opening, such that the first end face faces the opening side of the housing. The distance h between the groove and the first end face is greater than 0.55 mm and less than 2.35 mm.

2. The method for manufacturing an alkaline dry cell according to claim 1, wherein, The value obtained by subtracting the inner diameter of the shell from the maximum outer diameter of the first positive electrode granule is greater than 0 mm and less than 0.06 mm.

3. The method for manufacturing an alkaline dry cell according to claim 1 or 2, wherein, The depth of the groove is greater than 0.3 mm and less than 2.2 mm.

4. The method for manufacturing an alkaline dry cell according to any one of claims 1 to 3, wherein, The method for manufacturing the alkaline dry cell battery includes: In the fourth step, a negative electrode is disposed in the hollow portion of the positive electrode through a separator, and electrolyte is injected into the housing; and In the fifth step, a sealing unit is disposed on the stepped portion of the housing that passes through the groove, and the opening of the housing is sealed by the sealing unit.

5. An alkaline dry cell battery, comprising: A bottomed cylindrical shell with grooves; The hollow cylindrical positive electrode is connected to the housing in a region of the housing that is closer to the bottom than the groove; The negative electrode is disposed within the hollow portion of the positive electrode; An isolator is disposed between the positive electrode and the negative electrode; Electrolyte; and A sealing unit is disposed on a stepped portion of the housing that passes through the groove and seals the opening of the housing, wherein... The distance h between the groove and the end face of the positive electrode on the groove side is 0.55 mm or more and 2.35 mm or less. When the alkaline dry cell is disassembled to expose the positive electrode from the casing to the outside, the positive electrode has a tapered portion whose outer diameter decreases from the bottom side of the casing to the slot side, and in a cross section along the axial direction of the positive electrode, the inclination angle θ of the tapered portion relative to the axis of the positive electrode is more than 0.26° and less than 0.87°.

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