Negative electrode case for alkaline primary button battery, and alkaline primary button battery

Abstract

A negative electrode case (40) comprises a top portion (42) and a negative electrode case circumferential wall portion (44), and is inserted into the inside of a positive electrode case (20). An inner cylinder portion (45) of the negative electrode case circumferential wall portion (44) has a first curved portion (51) which extends curving downward from the outer circumferential edge of the top portion (42), a second curved portion (52) which extends curving radially outward from the lower end edge of the first curved portion (51), and a third curved portion (53) which extends curving downward from the outer circumferential edge of the second curved portion (52). The curvature radius of an outer surface (52a) of the second curved portion (52) in a vertical cross-section is greater than the curvature radius of an inner surface (51a) of the first curved portion (51) in the vertical cross-section and the curvature radius of an inner surface (53a) of the third curved portion (53) in the vertical cross-section. In the vertical cross-section, the angle θ formed by the axial direction and the common tangent (L) shared by the inner surface (51a) of the first curved portion (51) and the inner surface (53a) of the third curved portion (53) is not less than 40° and less than 60°.

Description

Negative electrode can for button-type alkaline primary battery, and button-type alkaline primary battery

[0001] The present invention relates to a negative electrode can for a button-type alkaline primary battery and a button-type alkaline primary battery. This application claims priority to Japanese Patent Application No. 2024-026881 filed on February 26, 2024, and Japanese Patent Application No. 2024-026392 filed on February 26, 2024, the contents of which are incorporated herein by reference.

[0002] Some button-type alkaline primary battery containers are sealed by crimping the openings of a pair of metal cans with a gasket sandwiched between them. For button-type alkaline primary batteries equipped with such containers, technologies have been developed to improve leak resistance in order to enhance reliability. For example, Patent Document 1 (Patent Document 1) describes an electrochemical cell in which the negative electrode can is formed into a two-tiered cylindrical shape with an inner diameter that decreases toward the lid. The first cylindrical section, which is closer to the lid, has a first inner curved surface that juts outward at a first vertex, and the second cylindrical section, which is farther from the lid, has a second inner curved surface that juts outward at a second vertex. The angle between the line connecting the first and second vertices and the bottom of the positive electrode can is between 15° and 45°. This is believed to reduce deformation of the negative electrode can when the positive electrode can is crimped against the peripheral wall of the negative electrode can.

[0003] Furthermore, some button alkaline primary batteries equipped with the above-described container have terminals attached to the metal can. For example, Patent Document 2 discloses a button battery having flat cylindrical positive and negative cans, gaskets that insulate and seal the positive and negative cans, and positive and negative terminals fixed to the bottom surfaces of the positive and negative cans, respectively.

[0004] JP 2014-157771 A International Publication No. 2022 / 196358

[0005] As electronic devices incorporating button-type alkaline primary batteries become smaller, there is a demand for smaller batteries themselves, as well as for increased battery capacity. Increasing the area of ​​the flat top of the negative electrode can increases the internal volume of the container, thereby increasing battery capacity. However, increasing the top area increases the inclination of the peripheral wall of the negative electrode can relative to the bottom of the positive electrode can, which can cause deformation of the negative electrode can when the positive electrode can is crimped.

[0006] Therefore, the present invention provides a negative electrode can for a button-type alkaline primary battery, which is capable of increasing the battery capacity while ensuring leakage resistance, and a button-type alkaline primary battery.

[0007] A negative electrode can for a button-type alkaline primary battery according to a first aspect of the present invention is a negative electrode can that is inserted into a positive electrode can, and that has a top that extends along a direction perpendicular to the axial direction, and a negative electrode can peripheral wall that extends from the outer circumferential edge of the top toward a first side in the axial direction, and the negative electrode can peripheral wall has an inner cylindrical portion that extends from the outer circumferential edge of the top toward an opening edge of the negative electrode can, a folded portion that is folded back radially outward from an edge of the inner cylindrical portion on the first side in the axial direction, and an outer cylindrical portion that extends from the radially outer end of the folded portion to a second side in the axial direction, and the inner cylindrical portion extends from the outer circumferential edge of the top toward a first side in the axial direction. the first curved portion extends in a curved manner toward the first side in the axial direction, a second curved portion extends in a curved manner radially outward from an edge of the first curved portion on the first side in the axial direction, and a third curved portion extends in a curved manner from an outer peripheral edge of the second curved portion toward the first side in the axial direction, wherein the radius of curvature of the outer surface of the second curved portion in a longitudinal cross section including the central axis is greater than the radius of curvature of the inner surface of the first curved portion in the longitudinal cross section and the radius of curvature of the inner surface of the third curved portion in the longitudinal cross section, and the angle formed by the common tangent of the inner surface of the first curved portion and the inner surface of the third curved portion in the longitudinal cross section and the axial direction is greater than or equal to 40° and less than 60°.

[0008] Here, if the angle between the common tangent and the axial direction in the vertical cross section is small, the portion of the inner tubular portion from the first curved portion to the third curved portion will be slightly upright in the axial direction, and when the opening edge of the positive electrode can is crimped inward, the force pressing the negative electrode can against the bottom of the positive electrode can will be insufficient, resulting in insufficient sealing. On the other hand, if the angle between the common tangent and the axial direction in the vertical cross section is large, the ratio of the outer diameter of the top to the outer diameter of the entire negative electrode can will decrease, thereby reducing the volume of the negative electrode can and the battery capacity. According to the first aspect, since the angle between the common tangent and the axial direction in the vertical cross section is 40° or more and less than 60°, when the positive electrode can is crimped, the negative electrode can will be strongly pressed against the bottom of the positive electrode can, ensuring reliable sealing and increasing battery capacity. Furthermore, because the radius of curvature of the outer surface of the second curved portion in the longitudinal cross section is larger than the radius of curvature of the inner surface of the first curved portion and the radius of curvature of the inner surface of the third curved portion, the angle can be increased while suppressing stress concentration at the first curved portion and the third curved portion when the opening edge of the positive electrode can is crimped while pressing the negative electrode can against the bottom of the positive electrode can. Furthermore, because the radius of curvature of the outer surface of the second curved portion in the longitudinal cross section is larger than the radius of curvature of the inner surface of the first curved portion and the radius of curvature of the inner surface of the third curved portion, the force generated when crimping the opening edge of the positive electrode can is more easily transmitted linearly from the third curved portion to the first curved portion. This allows for a stronger crimping force on the positive electrode can, ensuring reliable sealing. As a result, a negative electrode can for a button-type alkaline primary battery can be manufactured that can increase battery capacity while ensuring leakage resistance.

[0009] A second aspect of the present invention provides a negative electrode can for a button-type alkaline primary battery according to the first aspect, wherein the edge of the third curved portion on the first side in the axial direction is located closer to the first side in the axial direction than the edge of the outer tubular portion on the second side in the axial direction.

[0010] According to the second aspect, at least a portion of the third curved portion is located inside the outer tubular portion, so that a strong reaction force can be applied from the third curved portion to the peripheral wall of the positive electrode can, which has a drawn edge, via the outer tubular portion, thereby achieving reliable sealing and ensuring leakage resistance.

[0011] A negative electrode can for a button-type alkaline primary battery according to a third aspect of the present invention is the negative electrode can for a button-type alkaline primary battery according to the first or second aspect, wherein the axial size of the outer tubular portion in the longitudinal cross section may be smaller than the radial thickness of the folded-back portion.

[0012] According to the third aspect, the ratio of the radial thickness to the axial size is increased in the portion of the negative electrode can peripheral wall that is double-walled by the inner and outer cylindrical portions, thereby increasing durability against radial forces. This allows the positive electrode can to be tightly crimped, achieving reliable sealing and ensuring leakage resistance.

[0013] A button alkaline primary battery according to a fourth aspect of the present invention comprises: a negative electrode can for a button alkaline primary battery according to any one of the first to third aspects; a positive electrode can formed in a bottomed cylindrical shape and having a bottom and a positive electrode can peripheral wall extending from the outer peripheral edge of the bottom to the second side in the axial direction, with the negative electrode can for the button alkaline primary battery inserted inside; and a gasket arranged between the positive electrode can peripheral wall and the negative electrode can peripheral wall, and pressed against the outer peripheral surface of the negative electrode can by squeezing the opening edge of the positive electrode can.

[0014] According to the fourth aspect, the gap between the folded portion located at the edge of the opening of the negative electrode can and the bottom of the positive electrode can can be increased without increasing the gap between the top of the negative electrode can and the bottom of the positive electrode can, which allows the positive electrode disposed inside the positive electrode can to be made thicker along the bottom, thereby increasing the battery capacity and improving the impregnation of the electrolyte and the conductivity.

[0015] A button-type alkaline primary battery according to a fifth aspect of the present invention is the button-type alkaline primary battery according to the fourth aspect, wherein the gasket has an annular base extending along the opening edge of the negative electrode can, an outer wall extending from the base between the positive electrode can peripheral wall and the negative electrode can peripheral wall, and an inner circumferential portion extending radially inward from the base, and the radially inner edge of the inner circumferential portion may overlap the apex in the axial direction.

[0016] According to the fifth aspect, the opening edge of the negative electrode can is reliably covered with the gasket from the bottom side of the positive electrode can to the inside in the radial direction, so that the negative electrode can can be reliably protected when the opening is sealed.

[0017] A sixth aspect of the present invention provides a button-type alkaline primary battery comprising: an anode can formed in a cylindrical shape with a top having a central axis, the top extending in a direction perpendicular to the axial direction, and an anode can peripheral wall extending from the outer periphery of the top to a first side in the axial direction; a cathode can formed in a cylindrical shape with a bottom, the cathode can peripheral wall extending from the outer periphery of the bottom to a second side in the axial direction, the anode can being inserted inside; a gasket disposed between the cathode can peripheral wall and the anode can peripheral wall and pressed against the outer periphery of the anode can by squeezing an opening edge of the cathode can; and a cathode terminal joined to the top, the anode can peripheral wall including an inner cylindrical portion extending from the outer periphery of the top toward the opening edge of the anode can, and a folded portion folded back radially outward from an edge of the inner cylindrical portion on the first side in the axial direction. and an outer tube portion extending from the radially outer end of the folded-back portion toward the second side in the axial direction, wherein the inner tube portion has a first curved portion extending in a curved manner from the outer peripheral edge of the apex toward the first side in the axial direction, a second curved portion extending in a curved manner radially outward from an edge of the first curved portion on the first side in the axial direction, and a third curved portion extending in a curved manner from the outer peripheral edge of the second curved portion toward the first side in the axial direction, wherein a radius of curvature of an outer surface of the second curved portion in a vertical cross section including the central axis is greater than a radius of curvature of an inner surface of the first curved portion in the vertical cross section and a radius of curvature of an inner surface of the third curved portion in the vertical cross section, and an angle formed by a common tangent to the inner surfaces of the first curved portion and the third curved portion in the vertical cross section and the axial direction is greater than or equal to 40° and less than or equal to 50°.

[0018] Here, if the angle between the common tangent and the axial direction in the vertical cross section is small, the portion of the inner tube from the first curved portion to the third curved portion will be slightly upright in the axial direction, which may result in insufficient force pressing the negative electrode can against the bottom of the positive electrode can when the opening edge of the positive electrode can is drawn inward and crimped, resulting in insufficient sealing. On the other hand, if the angle between the common tangent and the axial direction in the vertical cross section is large, the ratio of the outer diameter of the top to the outer diameter of the entire negative electrode can will decrease, resulting in a reduced area of ​​the top, and insufficient bonding margin between the top of the negative electrode can and the negative electrode terminal. According to the sixth aspect, since the angle between the common tangent and the axial direction in the vertical cross section is between 40° and 50°, when the positive electrode can is crimped, the negative electrode can is firmly pressed against the bottom of the positive electrode can to ensure sealing, while suppressing a reduction in the outer diameter of the top of the negative electrode can to ensure a sufficient contact area with the negative electrode terminal. This allows the negative electrode terminal to be bonded to the top without misalignment even if the top is deformed, such as by a bulge or a dent. Furthermore, because the radius of curvature of the outer surface of the second curved portion in the longitudinal cross section is larger than the radius of curvature of the inner surface of the first curved portion and the radius of curvature of the inner surface of the third curved portion, the angle can be increased while suppressing stress concentration at the first curved portion and the third curved portion when the opening edge of the positive electrode can is crimped while pressing the negative electrode can toward the bottom of the positive electrode can. Furthermore, because the radius of curvature of the outer surface of the second curved portion in the longitudinal cross section is larger than the radius of curvature of the inner surface of the first curved portion and the radius of curvature of the inner surface of the third curved portion, the force generated when crimping the opening edge of the positive electrode can is more easily transmitted linearly from the third curved portion to the first curved portion. This increases the crimping force on the positive electrode can, enabling reliable sealing. This ensures leakage resistance while improving the dimensional accuracy of the terminal-equipped battery. Furthermore, because the reduction in the outer diameter of the top of the negative electrode can is suppressed, the joint between the top and the negative electrode terminal can be located closer to the periphery. This makes it difficult for the negative electrode terminal to come off the negative electrode can even when a load is applied to the negative electrode terminal, thereby improving the durability of the terminal-equipped battery.

[0019] According to the present invention, it is possible to provide a negative electrode can for a button-type alkaline primary battery, and a button-type alkaline primary battery, which are capable of increasing the battery capacity while ensuring leakage resistance.

[0020] It is a perspective view of the battery according to the embodiment. It is a side view of the battery according to the embodiment. It is a longitudinal sectional view of the battery according to the embodiment. It is an enlarged view of part IV in FIG.

[0021] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the following description, components having the same or similar functions will be denoted by the same reference numerals. Duplicate descriptions of those components may be omitted.

[0022] Fig. 1 is a perspective view of a battery according to an embodiment. Fig. 2 is a side view of the battery according to an embodiment. As shown in Figs. 1 and 2, the battery 1 according to the embodiment is a button-type alkaline primary battery. The battery 1 includes an exterior body 3 that is circular in a plan view, and a positive electrode terminal 11 and a negative electrode terminal 13 attached to the exterior body 3.

[0023] 3 is a longitudinal cross-sectional view of the battery according to the embodiment. As shown in Fig. 3, the exterior body 3 includes a positive electrode can 20 and a negative electrode can 40 attached to the positive electrode can 20 via an insulating gasket 30.

[0024] The exterior body 3 includes a cylindrical positive electrode can 20 with a bottom, an annular gasket 30 fitted inside the positive electrode can 20, and a cylindrical negative electrode can 40 with a top inserted into the opening of the positive electrode can 20 and attached to the positive electrode can 20 via the gasket 30. The positive electrode can 20 and the negative electrode can 40 are spaced apart with the gasket 30 sandwiched between them. The exterior body 3 is sealed by squeezing the opening edge 21 of the positive electrode can 20 by crimping, thereby pressing the gasket 30 against the outer circumferential surface of the negative electrode can 40. The positive electrode can 20, the negative electrode can 40, and the gasket 30 are arranged so that their respective central axes are aligned on a common axis. Hereinafter, this common axis will be referred to as axis O, the direction along axis O will be referred to as the axial direction, the direction extending radially from axis O perpendicular to axis O will be referred to as the radial direction, and the direction circumferentially around axis O will be referred to as the circumferential direction. The opening direction of the positive electrode can 20 in the axial direction is defined as the "upper side" (second side), and the opposite direction to the upper side is defined as the "lower side" (first side). A cross section that includes the axis O and is parallel to the axis O is referred to as a "longitudinal cross section."

[0025] The positive electrode can 20 is formed in a cylindrical shape that is open at the top. The positive electrode can 20 includes a disk-shaped bottom 22 that extends in a direction perpendicular to the axial direction, and a positive electrode can peripheral wall 24 that extends upward from the outer periphery of the bottom 22 all the way around toward the opening edge 21 of the positive electrode can 20. The positive electrode can 20 is formed by drawing a nickel-plated stainless steel plate.

[0026] The negative electrode can 40 is formed in a cylindrical shape that opens downward. An opening edge 41 of the negative electrode can 40 faces the upper surface of the bottom 22 of the positive electrode can 20 via a gasket 30. The opening edge 41 has a gap in the axial direction relative to the bottom 22 of the positive electrode can 20. The negative electrode can 40 has a disk-shaped top 42 that extends in a direction perpendicular to the axial direction, and a negative electrode can peripheral wall 44 that extends downward from the outer peripheral edge of the top 42 around the entire periphery. The negative electrode can 40 is formed by drawing or the like from a three-layer clad material having a nickel outer surface layer, a stainless steel metal layer, and a copper current collector layer.

[0027] The outer peripheral surface of the negative electrode can peripheral wall 44 extends from the outer peripheral edge of the top 42 toward the opening edge 41 of the negative electrode can 40 so as to expand in diameter. The negative electrode can peripheral wall 44 has an inner cylindrical portion 45 extending from the outer peripheral edge of the top 42 toward the opening edge 21 of the negative electrode can 40, a folded portion 46 folded radially outward from the lower end edge of the inner cylindrical portion 45, and an outer cylindrical portion 47 extending upward from the radially outer end of the folded portion 46.

[0028] FIG. 4 is an enlarged view of portion IV in FIG. 3 . As shown in FIG. 4 , the inner cylindrical portion 45 includes a first curved portion 51, a second curved portion 52, and a third curved portion 53. The first curved portion 51 is continuous with the outer peripheral edge of the apex portion 42. The first curved portion 51 extends downward from the outer peripheral edge of the apex portion 42. The first curved portion 51 is curved less than 90° in a vertical cross section. The second curved portion 52 extends radially outward from the lower edge of the first curved portion 51. The second curved portion 52 is curved less than 90° in a vertical cross section. The third curved portion 53 extends downward from the outer peripheral edge of the second curved portion 52. The lower edge of the third curved portion 53 is the lower edge of the inner cylindrical portion 45. The third curved portion 53 is curved less than 90° in a vertical cross section. In the following description of the shape of the inner cylindrical portion 45, unless otherwise specified, the shape will be described in vertical cross section.

[0029] The inner surface 51a of the first curved portion 51 is the entire concavely curved portion. The entire inner surface 51a of the first curved portion 51 is curved with a first radius of curvature. The entire outer surface of the first curved portion 51 is curved convexly. The outer surface 52a of the second curved portion 52 is the entire concavely curved portion. The entire outer surface 52a of the second curved portion 52 is curved with a second radius of curvature. The entire inner surface of the second curved portion 52 is curved convexly. The inner surface 53a of the third curved portion 53 is the entire concavely curved portion. The entire inner surface 53a of the third curved portion 53 is curved with a third radius of curvature. The entire outer surface of the third curved portion 53 is curved convexly. For example, the third radius of curvature is equal to the first radius of curvature. The second radius of curvature is greater than the first radius of curvature and the third radius of curvature.

[0030] The boundary between the first curved portion 51 and the second curved portion 52 is defined by a straight line passing through an end of the concave inner surface 51 a of the first curved portion 51 on the second curved portion 52 side and an end of the concave outer surface 52 a of the second curved portion 52 on the first curved portion 51 side. The boundary between the second curved portion 52 and the third curved portion 53 is defined by a straight line passing through an end of the concave outer surface 52 a of the second curved portion 52 on the third curved portion 53 side and an end of the concave inner surface 53 a of the third curved portion 53 on the second curved portion 52 side.

[0031] The inner cylindrical portion 45 is formed to satisfy the following conditions: In a longitudinal cross section, the angle θ formed between the common tangent L of the inner surface 51 a of the first curved portion 51 and the inner surface 53 a of the third curved portion 53 and the axial direction is greater than or equal to 40° and less than 60°. In other words, when the apex 42 is parallel to a direction perpendicular to the axial direction, the angle formed between the common tangent L and the apex 42 is greater than 30° and less than or equal to 50°. It is desirable that the angle θ formed between the common tangent L and the axial direction be greater than or equal to 43° and less than or equal to 57°. In the illustrated example, the angle θ formed between the common tangent L and the axial direction is 45°.

[0032] The folded portion 46 is provided on the opening edge 41 of the negative electrode can 40. The folded portion 46 extends radially outward, bending 180° from the lower end edge of the inner cylindrical portion 45. The lower surface of the folded portion 46 extends in a convex curved shape that protrudes downward in a vertical cross section.

[0033] The outer tube portion 47 extends upward from the folded portion 46 along the entire circumference. The outer tube portion 47 extends in the axial direction with a constant inner diameter and a constant outer diameter so as to surround the inner tube portion 45. The inner peripheral surface of the outer tube portion 47 may be in contact with the outer peripheral surface of the lower end of the inner tube portion 45, or may be slightly spaced apart from the outer peripheral surface of the inner tube portion 45. The upper edge 47a of the outer tube portion 47 is located above the lower edge of the third curved portion 53.

[0034] The axial size of outer tubular portion 47 is smaller than the radial thickness of folded portion 46 in vertical cross section. Furthermore, the axial size from opening edge 21 of negative electrode can 40 to upper edge 47a of outer tubular portion 47 is smaller than the radial thickness of folded portion 46 in vertical cross section.

[0035] The gasket 30 is disposed between the positive electrode can 20 and the negative electrode can 40. The gasket 30 includes a base 31 extending circumferentially along the opening edge 21 of the negative electrode can 40, an outer wall 32 extending from the base 31 between the positive electrode can peripheral wall 24 and the negative electrode can peripheral wall 44, and an inner peripheral portion 33 extending radially inward from the base 31. The gasket 30 is made of nylon, for example.

[0036] The base 31 is located below the folded portion 46 of the negative electrode can 40. The base 31 is disposed between the folded portion 46 of the negative electrode can 40 and the bottom 22 of the positive electrode can 20. The base 31 is in contact with the folded portion 46 but not with the bottom 22. The outer wall 32 is cylindrical. The outer wall 32 is in close contact with the positive electrode can peripheral wall 24 and the negative electrode can peripheral wall 44. The outer wall 32 is in contact with the opening edge 21 of the positive electrode can 20. The outer wall 32 is pressed against the outer peripheral surface and upper end surface of the outer tube portion 47 of the negative electrode can 40 by the positive electrode can peripheral wall 24, which is drawn by crimping. The outer wall 32 is not in contact with the inner tube portion 45 of the negative electrode can 40. The inner peripheral portion 33 protrudes radially inward beyond the folded portion 46. The inner peripheral portion 33 extends circumferentially over the entire circumference. The radially inner edge of the inner peripheral portion 33 is located radially inward of the outer peripheral edge of the top portion 42 of the negative electrode can 40 and overlaps the top portion 42 in the axial direction. A gate for injection molding may be formed in the inner peripheral portion 33.

[0037] 1 and 2, the positive electrode terminal 11 and the negative electrode terminal 13 are arranged to sandwich the exterior body 3 from both sides in the axial direction. The positive electrode terminal 11 and the negative electrode terminal 13 are formed from metal plates having good electrical conductivity, such as stainless steel.

[0038] The positive electrode terminal 11 is joined to the positive electrode can 20. The positive electrode terminal 11 has a rectangular positive electrode connection portion 11a arranged along the outer surface of the bottom 22 of the positive electrode can 20, an intermediate portion 11b extending substantially perpendicular to the positive electrode connection portion 11a, and a flat substrate connection portion 11c extending substantially perpendicular to the intermediate portion 11b. The positive electrode connection portion 11a is mechanically and electrically connected to the bottom 22 of the positive electrode can 20 by laser welding. The substrate connection portion 11c is a portion to be soldered to a connection surface such as a terminal pad formed on a substrate on which the battery 1 is mounted.

[0039] The negative electrode terminal 13 is joined to the negative electrode can 40. The negative electrode terminal 13 has a rectangular plate-shaped negative electrode connection portion 13a arranged along the outer surface of the top portion 42 of the negative electrode can 40, and a board connection portion 13c extending from one end of the negative electrode connection portion 13a. The negative electrode connection portion 13a is mechanically and electrically connected to the top portion 42 of the negative electrode can 40 by laser welding. For example, the negative electrode connection portion 13a is joined to the top portion 42 at multiple locations. The negative electrode connection portion 13a may be joined to the top portion 42 at different radial positions. The negative electrode connection portion 13a may be joined to the top portion 42 at different circumferential positions. The board connection portion 13c is formed so as to extend flush with the plate-shaped negative electrode connection portion 13a. The board connection portion 13c is a portion that is soldered to a connection surface, such as a terminal pad, formed on a board on which the battery 1 is mounted. Negative electrode terminal 13 is joined to negative electrode can 40 so that substrate connection portion 13c is adjacent to substrate connection portion 11c of positive electrode terminal 11. Negative electrode terminal 13 is generally flat and extends along the bottom surface of negative electrode can 40.

[0040] As shown in FIG. 3 , the battery 1 includes a positive electrode mixture 5, a negative electrode mixture 7, and a separator 9 disposed within an outer casing 3. The positive electrode mixture 5 and the negative electrode mixture 7 are disposed between a positive electrode can 20 and a negative electrode can 40, facing each other with the separator 9 interposed therebetween. The positive electrode mixture 5 is disposed along the bottom 22 of the positive electrode can 20. The positive electrode mixture 5 is disposed between the opening edge 41 of the negative electrode can 40 and the bottom 22 of the positive electrode can 20. The positive electrode mixture 5 is formed in a cylindrical shape corresponding to the internal shape of the positive electrode can 20 and is disposed substantially without gaps between the bottom 22 of the positive electrode can 20 and the peripheral wall 24 of the positive electrode can 20. The positive electrode mixture 5 is electrically connected to the inner surface of the positive electrode can 20. The separator 9 is disposed so as to cover the entire upper surface of the positive electrode mixture 5. The separator 9 is sandwiched between a gasket 30 and the positive electrode mixture 5. The negative electrode mixture 7 is disposed inside the negative electrode can 40. The negative electrode mixture 7 is placed on the positive electrode mixture 5 via a separator 9. The negative electrode mixture 7 is disposed between the separator 9 and the top 42 of the negative electrode can 40. The negative electrode mixture 7 is disposed with substantially no gap between the top 42 of the negative electrode can 40 and the negative electrode can peripheral wall 44. The negative electrode mixture 7 is electrically connected to the inner surface of the negative electrode can 40.

[0041] The positive electrode mixture 5 is formed into a pellet shape. The positive electrode mixture 5 contains a positive electrode active material, a conductive agent, an electrolyte, a binder, an additive, etc. The positive electrode active material is not particularly limited as long as it can be used as a positive electrode active material when zinc or a zinc alloy is used as a negative electrode active material. For example, the positive electrode active material may be silver oxide or manganese dioxide powder, or a mixture thereof. Alternatively, the positive electrode active material may be nickel oxyhydroxide alone, or nickel oxyhydroxide containing cobalt or the like as a solid solution. Graphite or the like can be used as the conductive additive. The additive may be a hydrogen storage alloy (LaNi ５ ) etc. can be used.

[0042] The negative electrode mixture 7 is in a gel state. The negative electrode mixture 7 contains, for example, a negative electrode active material, a conductivity stabilizer, a gelling agent, an electrolyte, a viscoelasticity adjuster, and additives (thickener, resin powder). For example, zinc powder or zinc alloy powder can be used as the negative electrode active material. Zinc oxide (ZnO) or the like can be used as the conductivity stabilizer. Furthermore, carboxymethyl cellulose, polyacrylic acid, or a mixture of carboxymethyl cellulose and polyacrylic acid is preferred as the gelling agent. The use of carboxymethyl cellulose or polyacrylic acid can improve the lyophilicity and liquid retention of the negative electrode mixture 7 with respect to the electrolyte.

[0043] The electrolyte may be an aqueous potassium hydroxide solution, an aqueous sodium hydroxide solution, or a mixture thereof. The viscoelasticity adjuster is blended to adjust the viscoelasticity of the negative electrode mixture 7 to a level that allows for good handling and improves productivity. A resin powder that does not react with the strongly alkaline electrolyte is used as the viscoelasticity adjuster. Here, the term "non-reactive with the electrolyte" refers to a state in which the material does not chemically react with the electrolyte and does not absorb the electrolyte.

[0044] An insulating film having high ion permeability and mechanical strength is used for the separator 9. Any separator conventionally used for the separator 9 of the battery 1 can be used without any restrictions as the separator 9, and examples thereof include glass such as alkali glass, borosilicate glass, quartz glass, and lead glass, and nonwoven fabrics made of resins such as polyphenylene sulfide (PPS), polyether ether ketone (PEEK), polyethylene terephthalate (PET), polyamideimide (PAI), polyamide, and polyimide (PI).

[0045] As described above, the negative electrode can peripheral wall 44 of the battery 1 of this embodiment has an inner cylindrical portion 45 extending from the outer peripheral edge of the top portion 42 toward the opening edge 41 of the negative electrode can 40, a folded portion 46 folded radially outward from the lower edge of the inner cylindrical portion 45, and an outer cylindrical portion 47 extending upward from the radially outer end of the folded portion 46. The inner cylindrical portion 45 has a first curved portion 51 that curves downward from the outer peripheral edge of the top portion 42, a second curved portion 52 that curves radially outward from the lower edge of the first curved portion 51, and a third curved portion 53 that curves downward from the outer peripheral edge of the second curved portion 52.

[0046] Here, if the angle θ between the axial direction and the common tangent L of the inner surface 51 a of the first curved portion 51 and the inner surface 53 a of the third curved portion 53 in the vertical cross section becomes small, the portion of the inner tubular portion 45 from the first curved portion 51 to the third curved portion 53 becomes slightly upright in the axial direction, and when the opening edge 21 of the positive electrode can 20 is drawn inward and crimped, the force pressing the negative electrode can 40 against the bottom 22 of the positive electrode can 20 is insufficient, which may result in insufficient sealing. On the other hand, if the angle θ between the common tangent L and the axial direction in the vertical cross section becomes large, the ratio of the outer diameter of the top to the outer diameter of the entire negative electrode can decreases, thereby reducing the volume of the negative electrode can and the battery capacity.

[0047] According to this embodiment, the angle θ between the common tangent L and the axial direction in the longitudinal section is 40° or more and less than 60°. Therefore, when the positive electrode can 20 is crimped, the negative electrode can 40 is pressed strongly against the bottom 22 of the positive electrode can 20, thereby ensuring a reliable seal and increasing the battery capacity.

[0048] Furthermore, since the radius of curvature of the outer surface 52a of the second curved portion 52 in the longitudinal cross section is larger than the radius of curvature of the inner surface 51a of the first curved portion 51 and the radius of curvature of the inner surface 53a of the third curved portion 53, it is possible to take a large angle θ while suppressing stress concentration in the first curved portion 51 and the third curved portion 53 when the opening edge 21 of the positive electrode can 20 is crimped while pressing the negative electrode can 40 toward the bottom 22 of the positive electrode can 20.

[0049] Furthermore, since the radius of curvature of the outer surface 52a of the second curved portion 52 in the longitudinal cross section is larger than the radius of curvature of the inner surface 51a of the first curved portion 51 and the radius of curvature of the inner surface 53a of the third curved portion 53, the force applied when crimping the opening edge 21 of the positive electrode can 20 is more likely to be transmitted linearly from the third curved portion 53 to the first curved portion 51. This makes it possible to increase the force with which the positive electrode can 20 is crimped, thereby ensuring reliable sealing. As a result, a negative electrode can 40 for a button-type alkaline primary battery can be manufactured that can increase battery capacity while maintaining leakage resistance.

[0050] The lower edge of the third curved portion 53 is located below the upper edge of the outer tubular portion 47. With this configuration, at least a portion of the third curved portion 53 is located inside the outer tubular portion 47, so that a strong reaction force can be applied from the third curved portion 53 via the outer tubular portion 47 to the positive electrode can peripheral wall portion 24, which has the drawn opening edge 21. This allows for reliable sealing and ensures leakage resistance.

[0051] The axial size of outer tubular portion 47 is smaller than the radial thickness of folded portion 46 in a longitudinal cross section. With this configuration, the ratio of radial thickness to axial size is increased at the portion of negative electrode can peripheral wall 44 that forms a double structure with inner tubular portion 45 and outer tubular portion 47, thereby increasing durability against radial forces. This makes it possible to strongly crimp positive electrode can 20, achieving reliable sealing and ensuring leakage resistance.

[0052] The gasket 30 has an annular base 31 extending along the opening edge 41 of the negative electrode can 40, an outer wall 32 extending from the base 31 between the positive electrode can peripheral wall 24 and the negative electrode can peripheral wall 44, and an inner peripheral portion 33 extending radially inward from the base 31. The radially inner edge of the inner peripheral portion 33 overlaps the top 42 in the axial direction. With this configuration, the opening edge 41 of the negative electrode can 40 is reliably covered by the gasket 30 from the bottom 22 side of the positive electrode can 20 to the radially inner side, thereby reliably protecting the negative electrode can 40 when sealing.

[0053] In button-type alkaline primary batteries, the metal can is prone to deformation due to factors such as the filling rate of the active material and electrolyte, the material of the metal can, and stress during crimping. When the metal can is deformed, the terminals joined to the metal can are likely to become misaligned, resulting in a problem of low dimensional accuracy as a battery with terminals.

[0054] Here, if the angle θ between the common tangent L and the axial direction in the longitudinal cross section of the battery 1 becomes large, the ratio of the outer diameter of the top 42 to the outer diameter of the entire negative electrode can 40 decreases, thereby reducing the area of ​​the top 42 and making it difficult to ensure a sufficient joint margin between the top 42 of the negative electrode can 40 and the negative electrode terminal 13. According to this embodiment, by setting the angle θ between the common tangent L and the axial direction in the longitudinal cross section to be 40° or more and 50° or less, when the positive electrode can 20 is crimped, the negative electrode can 40 is pressed firmly against the bottom 22 of the positive electrode can 20 to ensure sealing, while suppressing a decrease in the outer diameter of the top 42 of the negative electrode can 40 to ensure a sufficient contact area with the negative electrode terminal 13, and the negative electrode terminal 13 can be joined to the top 42 without shifting even if deformation such as a bulge or dent occurs in the top 42.

[0055] Furthermore, since the radius of curvature of the outer surface 52a of the second curved portion 52 in the longitudinal cross section is larger than the radius of curvature of the inner surface 51a of the first curved portion 51 and the radius of curvature of the inner surface 53a of the third curved portion 53, it is possible to take a large angle θ while suppressing stress concentration in the first curved portion 51 and the third curved portion 53 when the opening edge 21 of the positive electrode can 20 is crimped while pressing the negative electrode can 40 toward the bottom 22 of the positive electrode can 20.

[0056] Furthermore, because the radius of curvature of the outer surface 52a of the second curved portion 52 in the longitudinal cross section is larger than the radius of curvature of the inner surface 51a of the first curved portion 51 and the radius of curvature of the inner surface 53a of the third curved portion 53, the force applied when crimping the opening edge 21 of the positive electrode can 20 is more easily transmitted linearly from the third curved portion 53 to the first curved portion 51. This makes it possible to increase the force with which the positive electrode can 20 is crimped and ensure reliable sealing. As a result, the dimensional accuracy of the battery with terminals can be improved while ensuring leakage resistance.

[0057] Furthermore, because the reduction in the outer diameter of the top 42 of the negative electrode can 40 is suppressed, the joint between the top 42 and the negative electrode terminal 13 can be positioned closer to the outer periphery. This makes it less likely that the negative electrode terminal 13 will peel off from the negative electrode can 40 even if a load is applied to the negative electrode terminal 13. This improves the durability of the terminal-equipped battery 1.

[0058] A button-type silver oxide battery having the structure according to the embodiment described above, with an outer diameter of 7.9 mm and a thickness of 1.65 mm, was fabricated and tested. The positive electrode can of this button-type battery was made of nickel-plated stainless steel. The negative electrode can was made of a three-layer clad material consisting of nickel, stainless steel, and copper. The positive electrode can was 0.15 mm thick. The negative electrode can was 0.20 mm thick.

[0059] Here, as the negative electrode cans in this example, negative electrode cans in which the angle θ was set to 60° (Comparative Example), 55° (Example 1), 50° (Example 2), and 45° (Example 3) were used. A positive electrode mixture, a separator, a negative electrode mixture, and an electrolyte were placed inside the positive electrode can and the negative electrode can as shown in Fig. 3, and a gasket was attached, and the positive electrode can was crimped to seal, thereby producing a prototype battery.

[0060] In the preparation of the button battery, first, a positive electrode mixture for the positive electrode 5 was prepared using 92 mass % silver oxide (Ag ２ O), 5% by weight of manganese dioxide, 2% by weight of graphite, and 1% by weight of lanthanum nickel (LaNi ５) was mixed to prepare a cathode 5. The average particle size of the silver oxide was 10 μm, the average particle size of the manganese dioxide was 30 μm, the average particle size of the graphite was 15 μm, and the average particle size of the lanthanum nickel was 35 μm. Here, the average particle size of each was D50. Next, the cathode mixture consisting of the mixed particles was compression molded into a disk-shaped pellet to prepare the cathode 5.

[0061] Furthermore, as a negative electrode mixture to be used for the negative electrode 7, a mixture was obtained by mixing zinc powder adjusted to a range of 60 to 68 mass %, 2.5 mass % zinc oxide powder, 2.5 mass % CMC (carboxymethyl cellulose) as a gelling agent, and the balance being an aqueous potassium hydroxide solution as an electrolyte.

[0062] Next, the positive electrode 5 prepared by the above procedure was housed in a positive electrode can 20, a separator 9 was placed on the positive electrode 5, and a ring-shaped gasket 30 was press-fitted into the positive electrode can 20 and placed on the separator 9. Next, a negative electrode mixture was placed on the separator 9, and a negative electrode can 40 was placed on the negative electrode mixture with the gasket 30 interposed therebetween. The opening edge 21 of the positive electrode can 20 was then crimped to prepare the button-type alkaline primary battery 1 of this example. The separator 9 was made of polyethylene film and cellophane. The gasket 30 was made of polyamide.

[0063] For the button batteries of Examples 1 to 3 and Comparative Example obtained by the above procedure, the discharge capacity was measured at a discharge current of 50 μA and an end voltage of 1.2 V. The discharge capacity ratios of the discharge capacities obtained in Examples 1 to 3, when the discharge capacity in the Comparative Example was set to 1, are shown in Table 1 below. The values ​​in Table 1 are average values ​​of n=6 for each Example and Comparative Example.

[0064]

[0065] The results shown in Table 1 show that, compared to the comparative example in which the angle θ was 60°, sufficient discharge capacity was obtained in each example in which the angle θ was 45° to 55°.

[0066] Furthermore, the button type batteries of Examples 1 to 3 and Comparative Example were stored at 45° C. and 93% humidity for 60 days, and the appearances were observed. No leakage was observed in any of the batteries.

[0067] From the above test results, it was found that, for the negative electrode can peripheral wall portion 44 of the battery 1 of this embodiment, if the angle θ between the common tangent line L and the axial direction in the longitudinal cross section is 40° or more and less than 60°, the internal volume on the negative electrode can side can be increased, and it is possible to increase the battery capacity while ensuring leakage resistance.

[0068] The present invention is not limited to the above-described embodiment described with reference to the drawings, and various modifications are possible within the technical scope of the present invention. For example, in the above-described embodiment, the gasket 30 contacts the bottom 22 of the positive electrode can 20 via the separator 9 and the positive electrode mixture 5, but the gasket may also contact the bottom of the positive electrode can directly.

[0069] In the above embodiment, the entire outer surface of the first curved portion 51 is convexly curved in the longitudinal cross section, but the outer surface of the first curved portion may have a straight portion extending linearly in the longitudinal cross section toward the second curved portion. Also, in the above embodiment, the entire inner surface of the second curved portion 52 is convexly curved in the longitudinal cross section, but the inner surface of the second curved portion may have a straight portion extending linearly in the longitudinal cross section toward the first curved portion. Also, in the above embodiment, the entire inner surface of the second curved portion 52 is convexly curved in the longitudinal cross section, but the inner surface of the second curved portion may have a straight portion extending linearly in the longitudinal cross section toward the third curved portion. Also, in the above embodiment, the entire outer surface of the third curved portion 53 is convexly curved in the longitudinal cross section, but the outer surface of the third curved portion may have a straight portion extending linearly in the longitudinal cross section toward the second curved portion. Even in these cases, the boundary between the first curved portion and the second curved portion and the boundary between the second curved portion and the third curved portion in the longitudinal cross section are defined in the same manner as in the above embodiment.

[0070] In the above embodiment, the lower edge of the third curved portion 53 coincides with the lower edge of the inner tube portion 45, and the folded portion 46 extends from the lower edge of the third curved portion 53, but the third curved portion and the folded portion 46 do not have to be directly connected. For example, the inner tube portion may have a portion that extends linearly downward from the lower edge of the third curved portion and connects to the folded portion.

[0071] In addition, within the scope of the spirit of the present invention, it is possible to replace the components in the above-described embodiments with well-known components as appropriate, and the above-described embodiments and variations may be combined as appropriate.

[0072] According to the present invention, it is possible to provide a negative electrode can for a button-type alkaline primary battery, and a button-type alkaline primary battery, which are capable of increasing the battery capacity while ensuring leakage resistance.

[0073] DESCRIPTION OF SYMBOLS 1...Battery (button-type alkaline primary battery) 13...Negative electrode terminal 20...Positive electrode can 21...Opening edge of positive electrode can 22...Bottom 24...Positive electrode can peripheral wall 30...Gasket 31...Base 32...Outer wall 33...Inner periphery 40...Negative electrode can (negative electrode can for button-type alkaline primary battery) 41...Opening edge of negative electrode can 42...Top 44...Negative electrode can peripheral wall 45...Inner cylinder 46...Folded portion 47...Outer cylinder 51...First curved portion 51a...Inner surface of first curved portion 52...Second curved portion 52a...Outer surface of second curved portion 53...Third curved portion 53a...Inner surface of third curved portion L...Common tangent O...Axis (central axis)

Claims

1. A negative electrode can inserted into a positive electrode can, the negative electrode can having a topped cylindrical shape with a central axis, a top that extends in a direction perpendicular to the axial direction, and a negative electrode can peripheral wall that extends from the outer peripheral edge of the top to a first side in the axial direction, wherein the negative electrode can peripheral wall has: an inner cylindrical portion that extends from the outer peripheral edge of the top toward the opening edge of the negative electrode can; a folded portion that is folded back radially outward from an edge of the inner cylindrical portion on the first side in the axial direction; and an outer cylindrical portion that extends from the radially outer end of the folded portion to a second side in the axial direction, and the inner cylindrical portion has: a first curved portion that curves and extends from the outer peripheral edge of the top to the first side in the axial direction; a second curved portion that curves and extends radially outward from the edge of the first curved portion on the first side in the axial direction; and a third curved portion that curves and extends from the outer peripheral edge of the second curved portion to the first side in the axial direction. a radius of curvature of an outer surface of the second curved portion in a vertical cross section including the central axis is larger than a radius of curvature of an inner surface of the first curved portion in the vertical cross section and a radius of curvature of an inner surface of the third curved portion in the vertical cross section, and an angle formed by a common tangent to the inner surfaces of the first curved portion and the third curved portion in the vertical cross section and the axial direction is 40° or more and less than 60°.

2. The negative electrode can for a button-type alkaline primary battery according to claim 1, wherein an edge of the third curved portion on the first axial side is located closer to the first axial side than an edge of the outer tubular portion on the second axial side.

3. The negative electrode can for a button-type alkaline primary battery according to claim 1 or 2, wherein the axial size of the outer cylindrical portion is smaller than the radial thickness of the folded-back portion in the longitudinal cross section.

4. A button-type alkaline primary battery comprising: an anode can for a button-type alkaline primary battery according to claim 3; a cathode can formed in a cylindrical shape with a bottom, having a bottom and a cathode can peripheral wall extending from the outer periphery of said bottom to said second side in the axial direction, with said anode can for a button-type alkaline primary battery inserted inside; and a gasket disposed between said cathode can peripheral wall and said anode can peripheral wall, and pressed against the outer periphery of said anode can by squeezing the opening edge of said cathode can.

5. The button-type alkaline primary battery according to claim 4, wherein the gasket has an annular base extending along the opening edge of the negative electrode can, an outer wall extending from the base between the positive electrode can peripheral wall and the negative electrode can peripheral wall, and an inner circumferential portion extending radially inward from the base, and the radially inner edge of the inner circumferential portion overlaps the apex in the axial direction.

6. A negative electrode can having a topped cylindrical shape with a central axis, the top extending in a direction perpendicular to the axial direction, and a negative electrode can peripheral wall extending from the outer circumferential edge of the top to a first side in the axial direction; a positive electrode can having a bottomed cylindrical shape, the bottom and a positive electrode can peripheral wall extending from the outer circumferential edge of the bottom to a second side in the axial direction, the negative electrode can being inserted inside; a gasket disposed between the positive electrode can peripheral wall and the negative electrode can peripheral wall, the gasket being pressed against the outer circumferential surface of the negative electrode can by squeezing the opening edge of the positive electrode can; and a negative electrode terminal joined to the top, wherein the negative electrode can peripheral wall has: an inner cylindrical portion extending from the outer circumferential edge of the top toward the opening edge of the negative electrode can; a folded portion folded radially outward from the edge of the inner cylindrical portion on the first side in the axial direction; and an outer cylindrical portion extending from the radially outer end of the folded portion to the second side in the axial direction, a first curved portion extending and curving from the outer peripheral edge of the top portion toward the first side in the axial direction; a second curved portion extending and curving radially outward from an edge of the first curved portion on the first side in the axial direction; and a third curved portion extending and curving from the outer peripheral edge of the second curved portion toward the first side in the axial direction, wherein a radius of curvature of an outer surface of the second curved portion in a vertical cross section including the central axis is greater than a radius of curvature of an inner surface of the first curved portion in the vertical cross section and a radius of curvature of an inner surface of the third curved portion in the vertical cross section, and an angle formed by a common tangent to the inner surfaces of the first curved portion and the third curved portion in the vertical cross section and the axial direction is 40° or more and 50° or less.

Images