Cylindrical battery

Abstract

A shoulder section (29) of this cylindrical battery (10) has a flat surface (29a) at the upper side in the axial direction, said flat surface being roughly flat and roughly orthogonal to the axial direction. The shoulder section (29) has an annular protrusion (50) that faces a flange section (38) of a sealing body (17) in the axial direction. The protrusion (50) has a tapered shape in which, proceeding toward a tip (55), an outer peripheral surface (51) becomes progressively displaced radially inward and an inner peripheral surface (52) becomes progressively displaced radially outward. With this cylindrical battery (10), the shoulder section (29) can be easily connected electrically with an external component, and favorable sealing properties can easily be achieved.

Description

Cylindrical battery

[0001] The present disclosure relates to cylindrical batteries.

[0002] A conventional cylindrical battery is described in Patent Document 1. In this cylindrical battery, the open end of the outer can is crimped toward the bottom of the outer can as it approaches the front end of the outer can. This crimping increases the amount of compressive deformation of the gasket between the front end of the outer can and the flange of the sealing body, resulting in good sealing of the cylindrical battery.

[0003] Japanese Patent Application Laid-Open No. 2000-306557

[0004] External components are sometimes electrically connected to the shoulder of a cylindrical battery via leads or wires. In this context, if the shoulder extends toward the bottom of the exterior can as it approaches the front end, it becomes difficult to smoothly weld the leads or wires to the outer surface of the shoulder, making it difficult to smoothly connect the shoulder to external components.

[0005] On the other hand, if the open end of the outer can is crimped in a direction approximately perpendicular to the axial direction of the cylindrical battery, leads and wires can be more easily welded to the outer surface of the shoulder, but the sealing of the cylindrical battery is reduced.

[0006] Therefore, an object of the present disclosure is to provide a cylindrical battery in which the shoulder portion is easily electrically connected to an external component and has good sealing properties.

[0007] In order to solve the above problems, the cylindrical battery according to the present disclosure comprises: an electrode assembly in which an elongated positive electrode and an elongated negative electrode are wound with a separator interposed therebetween; a cylindrical portion including a shoulder portion extending radially inward at one axial end and a grooved portion recessed radially inward around the entire circumferential direction; and a bottom portion closing an opening on the other axial side of the cylindrical portion, the cylindrical portion housing the electrode assembly; and a sealing body closing the opening of the sealing body, wherein the shoulder portion has a substantially flat surface on one axial side that is substantially perpendicular to the axial direction, and the shoulder portion has an annular protrusion axially facing a flange portion of the sealing body, and the protrusion has a tapered shape in which the outer peripheral surface is displaced radially inward and the inner peripheral surface is displaced radially outward as it approaches the tip.

[0008] The requirement that the flat surface is approximately perpendicular to the axial direction is considered to be met when the flat surface is inclined at an angle of 3° or less with respect to a plane perpendicular to the axial direction.

[0009] According to the cylindrical battery according to the present disclosure, the shoulder portion can be easily electrically connected to an external component, and good sealing properties can be achieved.

[0010] Fig. 2 is an axial cross-sectional view of a cylindrical battery according to an embodiment of the present disclosure; Fig. 3 is an enlarged cross-sectional view of the periphery of the shoulder portion of Fig. 1; Fig. 4 is an axial cross-sectional view of the upper part of the outer can before the electrode assembly is inserted; Fig. 5 is an enlarged cross-sectional view corresponding to Fig. 2 of a cylindrical battery according to a first modified example; Fig. 6 is an enlarged cross-sectional view corresponding to Fig. 2 of a cylindrical battery according to a second modified example;

[0011] Hereinafter, an embodiment of a cylindrical battery according to the present disclosure will be described in detail with reference to the drawings. The cylindrical battery according to the present disclosure may be a primary battery or a secondary battery. Furthermore, the cylindrical battery according to the present disclosure may be a battery using an aqueous electrolyte or a battery using a nonaqueous electrolyte. Hereinafter, a nonaqueous electrolyte secondary battery (lithium ion battery) using a nonaqueous electrolyte will be exemplified as a cylindrical battery 10 according to one embodiment, but the cylindrical battery according to the present disclosure is not limited thereto, and the electrolyte may be an aqueous electrolyte.

[0012] It is anticipated from the beginning that new embodiments will be constructed by appropriately combining the features of the embodiments and variations described below. In the following embodiments, the same components are designated by the same reference numerals in the drawings, and redundant explanations will be omitted. Furthermore, multiple drawings include schematic diagrams, and the dimensional ratios of the length, width, height, etc. of each component between different drawings do not necessarily match. In this specification, the side of the sealing body 17 in the axial direction (height direction) of the cylindrical battery 10 is referred to as "upper," and the side of the bottom 31 of the outer can 16 in the axial direction is referred to as "lower." Furthermore, among the components described below, components not recited in the independent claims representing the highest concepts are optional components and not essential components.

[0013] FIG. 1 is an axial cross-sectional view of a cylindrical battery 10 according to one embodiment of the present disclosure. As shown in FIG. 1 , the cylindrical battery 10 includes an electrode assembly 14, a cylindrical outer can 16 with a bottom that houses the electrode assembly 14, and a sealing body 17 that closes the opening of the outer can 16. The outer can 16 houses a nonaqueous electrolyte together with the electrode assembly 14. The outer can 16 has a shoulder 29 at its upper end that is bent radially inward and extends inward. The outer can 16 has a groove 22 formed in its side wall. The sealing body 17 is supported by the groove 22 and closes the opening of the outer can 16.

[0014] The cylindrical battery 10 further includes a gasket 28 interposed between the exterior can 16 and the sealing body 17. The gasket 28 is a ring-shaped resin member attached to the outer periphery of the sealing body 17. The gasket 28 insulates the sealing body 17 from the exterior can 16 and seals the inside of the battery by filling the gap between the exterior can 16 and the sealing body 17. The gasket 28 is made of, for example, polyolefin.

[0015] The non-aqueous electrolyte includes a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent. Examples of the non-aqueous solvent include esters, ethers, nitriles, amides, and mixed solvents of two or more of these. The non-aqueous solvent may contain a halogen-substituted compound in which at least a portion of the hydrogen atoms of these solvents are substituted with halogen atoms such as fluorine. Examples of the non-aqueous solvent include ethylene carbonate (EC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), and mixed solvents thereof. Examples of the electrolyte salt include LiPF ６ The non-aqueous electrolyte is not limited to a liquid electrolyte, but may be a solid electrolyte.

[0016] The electrode assembly 14 has a positive electrode 11, a negative electrode 12, and a separator 13, and has a wound structure in which the positive electrode 11 and the negative electrode 12 are spirally wound with the separator 13 interposed therebetween. The positive electrode 11, the negative electrode 12, and the separator 13 are all long, strip-shaped bodies that are spirally wound and alternately stacked in the radial direction of the electrode assembly 14. The negative electrode 12 is formed to be slightly larger than the positive electrode 11 in order to prevent lithium deposition. That is, the negative electrode 12 is formed to be longer in the longitudinal direction and width direction than the positive electrode 11. The separator 13 is formed to be at least slightly larger than the positive electrode 11, and for example, two separators 13 are arranged to sandwich the positive electrode 11.

[0017] A positive electrode lead 20 and a negative electrode lead 21 are connected to the electrode body 14. The positive electrode lead 20 electrically connects the positive electrode 11 to the sealing body 17, and the negative electrode lead 21 electrically connects the negative electrode 12 to the bottom 31 of the outer can 16. In the example shown in Fig. 1 , the positive electrode lead 20 passes through the opening of the upper insulating plate 18 and extends toward the sealing body 17, and the negative electrode lead 21 passes outside the lower insulating plate 19 and extends toward the bottom 31 of the outer can 16.

[0018] The positive electrode 11 has a positive electrode core and a positive electrode mixture layer formed on at least one surface of the positive electrode core. The positive electrode core may be made of a foil of a metal, such as aluminum or an aluminum alloy, that is stable within the potential range of the positive electrode 11, or a film with such a metal disposed on the surface. The positive electrode mixture layer preferably contains a positive electrode active material, a conductive agent such as acetylene black, and a binder such as polyvinylidene fluoride (PVdF), and is preferably formed on both sides of the positive electrode core. The positive electrode active material may be, for example, a lithium transition metal composite oxide containing Ni, Co, Mn, Al, or the like. The positive electrode lead 20 is connected to the positive electrode 11. The positive electrode lead 20 is preferably directly bonded to the positive electrode core by ultrasonic welding or the like.

[0019] The negative electrode 12 has a negative electrode core and a negative electrode mixture layer formed on at least one surface of the negative electrode core. The negative electrode core may be made of a foil of a metal stable within the potential range of the negative electrode 12, such as copper or a copper alloy, or a film with such a metal disposed on the surface. The negative electrode mixture layer preferably contains a negative electrode active material and a binder such as styrene-butadiene rubber (SBR) or PVdF, and is preferably formed on both sides of the negative electrode core. Examples of the negative electrode active material include graphite and silicon-containing compounds. The negative electrode lead 21 is preferably directly bonded to the negative electrode core by ultrasonic welding or the like. The negative electrode 12 may be electrically connected to the outer can 16 by contacting the negative electrode core with the inner surface of the outer can 16.

[0020] The outer can 16 is generally made of a metal primarily composed of iron, such as nickel-plated iron. The outer can 16 may also be made of a metal primarily composed of aluminum or the like. The outer can 16 has a cylindrical portion 39 and a bottom 31. The cylindrical portion 39 includes an annular grooved portion 22 and an annular shoulder portion 29. The grooved portion 22 is formed by spinning a portion of the cylindrical portion 39 to recess it radially inward around the entire circumferential direction. The shoulder portion 29 is formed when the upper end (one axial end) of the cylindrical portion 39 is bent radially inward and crimped to the peripheral edge portion 33 of the sealing body 17, and extends radially inward at the upper end of the cylindrical portion 39.

[0021] The sealing body 17 is clamped by crimping between the shoulder portion 29 and the grooved portion 22 with the gasket 28 interposed therebetween, and is fixed to the outer can 16. The grooved portion 22 is formed at a position spaced a predetermined length from the upper end of the outer can 16. The predetermined length is, for example, a length equivalent to 1 to 20% of the axial length of the outer can 16. The gasket 28 is strongly compressed by the shoulder portion 29, and a portion of the gasket 28 protrudes radially inward from between the shoulder portion 29 and the sealing body 17.

[0022] The sealing body 17 has a structure in which a terminal plate 23, a lower valve body 24, an insulating plate 25, an upper valve body 26, and a sealing plate 27 are stacked in this order from the electrode body 14 side. Each component constituting the sealing body 17 has, for example, a disk or ring shape, and each component except for the insulating plate 25 is electrically connected to one another. The sealing plate 27 has a convex shape with a radially central portion protruding outward. The convex portion 27a of the sealing plate 27 includes a ring-shaped inclined portion and a flat top surface portion surrounded by the inclined portion. One or more air vents 27b are formed in the top surface portion. The convex portion of the sealing plate may have a cylindrical portion instead of the ring-shaped inclined portion.

[0023] The lower valve body 24, insulating plate 25, and upper valve body 26 constitute a current interruption mechanism. The lower valve body 24 and upper valve body 26 are connected at their respective centers, with the insulating plate 25 interposed between their respective peripheral edges. If an abnormality occurs in the cylindrical battery 10 and the internal pressure rises, the lower valve body 24 deforms and pushes the upper valve body 26 toward the sealing plate 27, causing it to break, interrupting the current path between the lower valve body 24 and the upper valve body 26. If the internal pressure rises further, the upper valve body 26 breaks, causing gas to be released through the vent hole 27b in the sealing plate 27.

[0024] In this embodiment, the positive electrode lead 20 is connected to the underside of the terminal plate 23 by welding, ultrasonic welding, or the like, and the sealing plate 27, which is the top plate of the sealing body 17 electrically connected to the terminal plate 23, serves as the positive electrode terminal. The negative electrode lead 21 is connected to the inner surface of the bottom 31 of the outer can 16 by welding, ultrasonic welding, or the like, and the outer can 16 serves as the negative electrode terminal.

[0025] The structure of the area around the shoulder 29 of the cylindrical battery 10 and a manufacturing method for the cylindrical battery 10 will be described below with reference to Figures 2 and 3. Figure 2 is an enlarged cross-sectional view of the area around the shoulder 29 in Figure 1. As shown in Figure 2, the shoulder 29 has a substantially flat surface 29a on the upper axial side (one axial side) that is substantially perpendicular to the axial direction. The flat surface 29a is inclined at an angle of 3° or less, preferably 1° or less, with respect to a plane perpendicular to the axial direction. Providing the flat surface 29a on the upper axial end surface of the shoulder 29 makes it easier to weld leads or wires to the flat surface 29a, facilitating smooth connection of the shoulder 29 to external components.

[0026] Shoulder portion 29 has an annular protrusion 50 that axially faces an annular flange portion 38 of sealing body 17. Protrusion 50 has a shape that tapers toward tip 55. As it approaches tip 55, outer peripheral surface 51 of protrusion 50 is displaced radially inward, and inner peripheral surface 52 of protrusion 50 is displaced radially outward.

[0027] By providing a tapered protrusion 50 below the shoulder portion 29, the force with which the shoulder portion 29 compresses the gasket 28 onto the flange portion 38 at the tip 55 of the protrusion 50 is increased, resulting in good sealing of the cylindrical battery 10.

[0028] Furthermore, by forming the protrusions 50 so that the outer peripheral surface 51 of the protrusions 50 displaces radially inward as it approaches the tip 55, and the inner peripheral surface 52 of the protrusions 50 displaces radially outward as it approaches the tip 55, the gasket 28 is less likely to lose excessive material in the radial direction due to the force received from the protrusions 50 when crimping to form the shoulder 29. This reduces the likelihood of localized stress concentration due to the gasket 28 on the shoulder 29 of the outer can 16, particularly on the upper corners of the outer can, improving the durability of the cylindrical battery 10.

[0029] In order to increase the force with which the gasket 28 is sandwiched between the protrusions 50 and the flange portion 38, it is preferable that the entire protrusion 50 is positioned so as to overlap the flat surface 29a in the axial direction. However, a portion of the radially outer side of the protrusion 50 may also overlap in the axial direction with a curved portion located radially outward of the upper part of the outer can 16. In addition, in order to increase the force with which the gasket 28 is sandwiched between the protrusions 50 and the flange portion 38, it is preferable that the outer peripheral surface 51 is connected to a curved surface located at a corner of the outer can 16, and the inner peripheral surface 52 is connected to the tip of the inner surface of the outer can 16.

[0030] The first axial thickness t1 at a first location on the shoulder 29 where the tip 55 of the projection 50 is located is preferably 1.1 to 1.6 times the second axial thickness t2 at a second location on the shoulder 29 where the radially outer end 56 of the projection 50 is located. When the first thickness t1 is 1.1 times or more the second thickness t2, the force compressing the gasket 28 by the shoulder 29 and flange 38 is likely to be large enough to achieve excellent sealing of the cylindrical battery 10. Furthermore, when the first thickness t1 is 1.6 times or less the second thickness t2, excessive radial loss of the gasket 28 during crimping to form the shoulder 29 is effectively suppressed. Therefore, localized stress concentration due to the gasket 28 at the upper corner (upper curved portion) of the outer can 16 is effectively suppressed, resulting in excellent durability of the cylindrical battery 10.

[0031] In a half cross-section taken along the axial direction of the cylindrical battery 10, the outer peripheral surface 51 and inner peripheral surface 52 of the protrusion 50 both have a substantially linear shape. In the half cross-section, a first line y1 representing the outer peripheral surface 51 and a second line y2 representing the inner peripheral surface 52 intersect at a single point, with this intersection being the tip 55 of the protrusion 50. In the half cross-section, the angle θ formed by the third line y3 representing the flat surface 29a and the first line y1 representing the outer peripheral surface 51 is preferably between 5° and 20°. In a plan view taken along the axial direction of the cylindrical battery 10, the protrusion 50 may be annular, but it is preferable that both the protrusion 50 and the tip 55 be circular.

[0032] When the angle θ formed by the third line y3 and the first line y1 is 5° or greater, the force compressing the gasket 28 at the shoulder 29 and flange 38 is likely to be large enough to achieve excellent sealing of the cylindrical battery 10. Furthermore, when the angle θ formed by the third line y3 and the first line y1 is 20° or less, excessive radial loss of the gasket 28 is effectively suppressed when crimping to form the shoulder 29. Therefore, localized stress concentration by the gasket 28 at the upper corner of the outer can 16 is effectively suppressed, and the durability of the cylindrical battery 10 is likely to be excellent.

[0033] 3 is an axial cross-sectional view of the upper part of the outer can 16 before the electrode assembly 14 is inserted. As shown in Fig. 3, the upper end of the outer can 16 before the electrode assembly 14 is inserted is displaced radially outward as it moves axially upward. As a result, even though a thick protrusion 50 is provided on the upper side of the outer can 16, the protrusion-forming portion 64 of the outer can 16 is not positioned radially inward of the inner circumferential surface of the cylindrical portion 65 on the lower side of the outer can 16.

[0034] The cylindrical battery 10 is fabricated as follows, for example, using the outer can 16 shown in Figure 3. First, the electrode assembly 14 (see Figure 1) is inserted into the outer can 16. Because the protrusion-forming portion 64 of the outer can 16 is not located radially inward of the inner circumferential surface of the cylindrical portion 65 on the lower side of the outer can 16, the insertion of the electrode assembly 14 into the outer can 16 is not hindered by the protrusion-forming portion 64, and the electrode assembly 14 can be smoothly inserted into the outer can 16. Next, the outer circumferential surface of the outer can 16 is drawn so that it becomes linear along the axial direction when viewed in cross section in the axial direction.

[0035] Next, a spinning process is performed to form an annular groove 22 (see FIG. 1) in the outer can 16, and then the sealing body 17 (see FIG. 1) is inserted into the outer can 16 until it contacts the upper part of the inner surface of the annular groove 22. Finally, the cylindrical battery 10 is produced by crimping to form a flat surface 29a (see FIG. 2) on the upper side of the shoulder 29 (see FIG. 2).

[0036] The drawing process can be performed at any timing after the electrode body 14 is inserted into the outer can 16. For example, the drawing process may be performed after the grooved portion 22 is formed by spinning and before the sealing body 17 is inserted into the outer can.

[0037] The present disclosure is not limited to the above-described embodiment and its modifications, and various improvements and modifications are possible within the scope of the claims of the present application and their equivalents.

[0038] Fig. 4 is an enlarged cross-sectional view corresponding to Fig. 2 of a cylindrical battery 110 of a first modified example, and Fig. 5 is an enlarged cross-sectional view corresponding to Fig. 2 of a cylindrical battery 210 of a second modified example. As shown in Fig. 4, the tip 155 of the annular protrusion 150 provided on the shoulder 129 of the outer can 116 may be configured with a flat surface extending approximately parallel to the radial direction (approximately perpendicular to the axial direction). Also, as shown in Fig. 5, the outer and inner peripheral surfaces of the protrusion 250 provided on the shoulder 229 of the outer can 216 may be outwardly convex curved.

[0039] The cylindrical battery of the present disclosure may also have the following configurations: Configuration 1: A cylindrical battery comprising: an electrode assembly in which an elongated positive electrode and an elongated negative electrode are wound with a separator interposed therebetween; a cylindrical outer can with a bottom that houses the electrode assembly and has a shoulder portion extending radially inward at one axial end and a tubular portion including a grooved portion recessed radially inward around the entire circumferential circumference, and a bottom portion that closes an opening of the cylindrical portion on the other axial side; and a seal body that closes the opening of the outer can, wherein the shoulder portion has a substantially flat surface on one axial side that is substantially perpendicular to the axial direction, and the shoulder portion has an annular protrusion that faces a flange portion of the seal body in the axial direction, and the protrusion has a tapered shape in which an outer peripheral surface is displaced radially inward and an inner peripheral surface is displaced radially outward as it approaches a tip end. Configuration 2: The cylindrical battery according to Configuration 1, wherein a first thickness in the axial direction at a first location on the shoulder where the tip of the protrusion is located is 1.1 to 1.6 times the second thickness in the axial direction at a second location on the shoulder where the outer radial end of the protrusion is located.Configuration 3: The cylindrical battery according to Configuration 1 or 2, wherein the outer peripheral surface has a substantially linear shape in a cross section in the axial direction.Configuration 4: The cylindrical battery according to Configuration 3, wherein an angle formed between a line representing the flat surface and a line representing the outer peripheral surface in the cross section is 5° to 20°.Configuration 5: The cylindrical battery according to any one of Configurations 1 to 4, wherein the outer peripheral surface is connected to a curved surface located at a corner of the outer can, and the inner peripheral surface is connected to the tip of the outer can.

[0040] 10,110,210 Cylindrical battery, 11 Positive electrode, 12 Negative electrode, 13 Separator, 14 Electrode body, 16,116,216 Outer can, 17 Sealing body, 18 Upper insulating plate, 19 Lower insulating plate, 20 Positive electrode lead, 21 Negative electrode lead, 22 Grooved portion, 23 Terminal plate, 24 Lower valve body, 25 Insulating plate, 26 Upper valve body, 27 Sealing plate, 27a Convex portion, 27b Vent, 28 Gasket, 29,129,229 Shoulder portion, 29a Flat surface, 31 Bottom portion, 33 Peripheral edge portion, 38 Flange portion, 39 Cylindrical portion, 50,150,250 Protrusion, 51 Outer peripheral surface of protrusion 52 inner peripheral surface of protrusion, 55 tip of protrusion, 56 outer end of protrusion, 64 protrusion forming portion, 65 cylindrical portion, 155 flat surface, t1 first thickness, t2 second thickness, y1 first straight line, y2 second straight line, y3 third straight line, θ angle formed by the first straight line and the third straight line.

Claims

1. A cylindrical battery comprising: an electrode assembly in which a long positive electrode and a long negative electrode are wound with a separator interposed therebetween; a bottomed, cylindrical outer can containing the electrode assembly, the cylindrical can having a shoulder extending radially inward at one end in the axial direction and a grooved portion recessed radially inward around the entire circumferential circumference, and a bottom closing an opening of the cylindrical portion on the other side in the axial direction; and a seal body closing an opening of the outer can, wherein the shoulder has a substantially flat surface substantially perpendicular to the axial direction on one side in the axial direction, the shoulder has an annular protrusion facing the axial direction on a flange portion of the seal body, and the protrusion has a tapered shape in which the outer circumferential surface is displaced radially inward and the inner circumferential surface is displaced radially outward as it approaches the tip.

2. The cylindrical battery as described in claim 1, wherein a first axial thickness at a first point on the shoulder where the tip of the protrusion is located is between 1.1 and 1.6 times a second axial thickness at a second point on the shoulder where the radially outer end of the protrusion is located.

3. The cylindrical battery according to claim 1 or 2, wherein the outer circumferential surface has a substantially linear shape in a cross section along the axial direction.

4. The cylindrical battery according to claim 3, wherein in the cross section, an angle formed between a straight line representing said flat surface and a straight line representing said outer circumferential surface is between 5° and 20°.

5. The cylindrical battery according to claim 1 or 2, wherein the outer peripheral surface is connected to a curved surface located at a corner of the outer can, and the inner peripheral surface is connected to a tip of the outer can.

Images