Cylindrical battery

Abstract

This cylindrical battery (10) comprises: an electrode body (14) in which a positive electrode (11) and a negative electrode (12) are wound up with a separator (13) therebetween and at least a part of the outermost circumferential surface in the circumferential direction is constituted from a negative electrode core body of the negative electrode (12); a cylindrical, bottomed outer casing (16) that accommodates the electrode body (14); a sealing body (17) for sealing the opening of the outer casing (16); and a current collector plate (40) joined to both the negative electrode core body positioned on the outermost circumferential surface and the inner circumferential surface of the outer casing (16).

Description

Cylindrical battery

[0001] The present disclosure relates to cylindrical batteries.

[0002] A conventional cylindrical battery is described in Patent Document 1. This cylindrical battery includes an electrode assembly, a cylindrical outer can with a bottom that houses the electrode assembly, a sealing body that closes the opening of the outer can, and a gasket that is sandwiched between the outer can and the sealing body. The electrode assembly has a structure in which a positive electrode and a negative electrode are wound with a separator interposed therebetween. The positive electrode and the sealing body are electrically connected via a positive electrode lead, and the negative electrode and the bottom of the outer can are electrically connected via a negative electrode lead.

[0003] Japanese Patent Application Publication No. 09-274923

[0004] Cylindrical batteries are sometimes used as battery packs. In a battery pack, multiple cylindrical batteries 310 are connected to each other, as shown in FIG. 4 or FIG. 5 . In both connection structures, the sealing body 317 is used as the positive terminal. In the connection structure shown in FIG. 4 , the bottom 331 of the outer can is used as the negative terminal, and multiple cylindrical batteries 310 are arranged so that the orientations of the positive and negative terminals alternate. A bus bar 380 is connected to adjacent positive and negative terminals. Both the positive and negative terminals function as external terminals. On the other hand, in the connection structure shown in FIG. 5 , the shoulder 329 of the outer can is used as the negative terminal, and multiple cylindrical batteries 310 are arranged in the same orientation. Therefore, the bus bars 385 connecting adjacent positive and negative terminals are arranged on the same axial side.

[0005] When the shoulder of the outer can of the cylindrical battery of Patent Document 1 is used as the external terminal, a current path from the bottom of the outer can to the shoulder is added to the current path from the negative electrode lead to the external terminal, compared to when the bottom of the outer can is used as the external terminal. Because the current path from the negative electrode lead to the external terminal is thus increased, the electrical resistance of the cylindrical battery increases, hindering higher output. Therefore, an object of the present disclosure is to provide a cylindrical battery that can reduce the electrical resistance when the shoulder of the outer can is used as the external terminal.

[0006] In order to solve the above problems, the cylindrical battery according to the present disclosure comprises an electrode body in which a first electrode and a second electrode are wound with a separator interposed therebetween, and at least a portion of the circumferential direction of the outermost peripheral surface is constituted by a core body of the first electrode, a cylindrical outer can with a bottom that houses the electrode body, a sealing body that closes the opening of the outer can, and a current collector plate joined to both the core body located on the outermost peripheral surface and the inner peripheral surface of the outer can.

[0007] According to the cylindrical battery according to the present disclosure, when the shoulder portion of the outer can is used as an external terminal, resistance can be reduced.

[0008] Fig. 1 is an axial cross-sectional view of a cylindrical battery according to an embodiment of the present disclosure; Fig. 2 is a cross-sectional view taken along line A-A in Fig. 1; Fig. 3 is an axial cross-sectional view of a cylindrical battery according to a modified example; Fig. 4 is a diagram illustrating a connection structure of a plurality of cylindrical batteries connected to each other with the bottom of an outer can as the negative terminal within a battery pack; Fig. 5 is a diagram illustrating a connection structure of cylindrical batteries connected to each other with the shoulder of an outer can as the negative terminal within a battery pack.

[0009] 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. It may also be a battery using an aqueous electrolyte or a battery using a non-aqueous electrolyte. Hereinafter, a non-aqueous electrolyte secondary battery (lithium ion battery) using a non-aqueous 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 also be an aqueous electrolyte.

[0010] 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.

[0011] 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, a sealing body 17 that closes the opening of the outer can 16, and a current collector plate 40 that is disposed between the outermost peripheral surface of the electrode assembly 14 and the inner peripheral surface of the outer can 16. The outer can 16 houses a nonaqueous electrolyte together with the electrode assembly 14.

[0012] The outer can 16 has an annular shoulder 29 at its upper end that is bent radially inward and extends inward. The outer can 16 also has an annular groove 22 formed in its side wall, and the sealing body 17 is supported by the groove 22 to close the opening of the outer can 16.

[0013] 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, and insulates the sealing body 17 from the exterior can 16. The gasket 28 also seals the gap between the exterior can 16 and the sealing body 17, sealing the inside of the battery. The gasket 28 is made of, for example, polyolefin.

[0014] 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.

[0015] 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.

[0016] The positive electrode 11 has a long positive electrode core and a positive electrode mixture layer formed on at least one surface of the positive electrode core. The positive electrode core can be 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 layer. 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 formed on both sides of the positive electrode core. For example, a lithium transition metal composite oxide containing Ni, Co, Mn, Al, etc. is used as the positive electrode active material.

[0017] The negative electrode 12 has a long negative electrode core and a negative electrode mixture layer formed on at least one surface of the negative electrode core. The negative electrode core can be made of a foil of a metal, such as copper or a copper alloy, that is stable within the potential range of the negative electrode 12, or a film with such a metal disposed on the surface layer. The negative electrode mixture layer 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. The negative electrode active material can be, for example, graphite or a silicon-containing compound.

[0018] A positive electrode lead 20 is connected to the electrode body 14. The positive electrode lead 20 electrically connects the positive electrode 11 and the sealing body 17. The positive electrode lead 20 is joined to the positive electrode core by ultrasonic welding or the like. In the example shown in FIG. 1 , the positive electrode lead 20 extends from the positive electrode 11 through an opening in the insulating plate 18 toward the sealing body 17. One end of the positive electrode lead 20 is joined to the positive electrode core by ultrasonic welding or the like, and the other end of the positive electrode lead 20 is joined to the underside of the sealing body 17 by welding, ultrasonic welding or the like.

[0019] The cylindrical battery 10 includes an insulating plate 19 disposed between the electrode assembly 14 and the bottom 31, thereby insulating the electrode assembly 14 from the bottom 31. The negative electrode core includes an outermost peripheral surface arrangement portion 35 that constitutes at least a portion of the circumferential direction of the outermost peripheral surface of the electrode assembly 14. The current collector 40 is a metal plate member and is disposed between the radially outer surface of the outermost peripheral surface arrangement portion 35 and the inner peripheral surface of the outer can 16. FIG. 2 is a cross-sectional view taken along line A-A in FIG. 1. As shown in FIG. 2, the outer radial surface of the current collector 40 has a generally arc-shaped cross section, and the inner radial surface of the current collector 40 also has a generally arc-shaped cross section. The current collector 40 is joined to the radially outer surface of the outermost peripheral surface arrangement portion 35 by ultrasonic welding or the like, and is joined to the inner peripheral surface of the outer can 16 by laser welding or the like. The negative electrode 12 and the cylindrical portion 39 of the outer can 16 are electrically connected via the current collector 40.

[0020] The outer can 16 is generally made of a metal primarily composed of iron, but may also be made of a metal primarily composed of aluminum or the like. As shown in Fig. 1 , the outer can 16 has a cylindrical portion 39 and a bottom portion 31. The cylindrical portion 39 includes an annular grooved portion 22 and an annular shoulder portion 29. The grooved portion 22 is formed by applying a spinning process to a portion of the cylindrical portion 39 around the entire circumference to recess it radially inward. The shoulder portion 29 is formed when the upper end of the cylindrical portion 39 is bent radially inward and crimped onto the peripheral edge portion 33 of the sealing body 17, and protrudes radially inward.

[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 extends 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 layered 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 sloped portion and a flat top surface portion surrounded by the sloped portion. One or more air vents 27b are formed in the top surface 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 the upper valve body 26 are connected at their respective centers, with the insulating plate 25 interposed between their respective peripheral edges. In this case, if an abnormality occurs in the battery 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, thereby 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 discharged through the vent hole 27b in the sealing plate 27.

[0024] Positive electrode lead 20 is connected to the underside of terminal plate 23, and sealing plate 27, which is the top plate of sealing body 17 electrically connected to terminal plate 23, serves as the positive electrode terminal. In cylindrical battery 10, it is assumed that shoulder 29 of tubular portion 39, which is electrically connected to negative electrode 12 via current collector plate 40, will be used as the negative electrode terminal.

[0025] The cylindrical battery 10 can be fabricated, for example, by the following procedure. First, an electrode body 14 is prepared, in which at least a portion of the circumferential direction of the outermost surface is made of a negative electrode core, and a positive electrode lead 20 is joined to the positive electrode core by ultrasonic welding. Next, a current collector plate 40 is joined by ultrasonic welding to an outermost surface arrangement portion 35 of the negative electrode core that constitutes at least a portion of the circumferential direction of the outermost surface of the electrode body 14. Before winding the negative electrode 11 together with the positive electrode 12 and separator 13, the current collector plate 40 may be joined to the position of the negative electrode core that will become the outermost surface arrangement portion 35.

[0026] Thereafter, the electrode body 14 is inserted into the cylindrical outer can 16 with a bottom, and the outer can 16 is then drawn to reduce its diameter, or a rod is inserted into the hollow portion of the electrode body 14 to press the current collector plate 40 against the inner peripheral surface of the outer can 16. Then, with the current collector plate 40 in contact with the inner peripheral surface of the outer can 16, a laser beam is irradiated from outside the outer can 16 to join the current collector plate 40 and the inner peripheral surface of the outer can 16.

[0027] Next, after forming the grooved portion 22, the positive electrode lead 20 is joined to the underside of the sealing body 17 by welding or ultrasonic welding. Finally, the opening of the outer can 16 is sealed with the sealing body 17 by crimping, thereby completing the cylindrical battery 10.

[0028] The current collector plate 40 will now be described in detail with further reference to FIGS.

[0029] 1 , the current collector 40 is bonded to both the outermost peripheral portion 35 of the negative electrode core, which is located on the outermost peripheral surface of the electrode assembly 14, and the inner peripheral surface of the outer can 16. Therefore, when the shoulder 29 is used as the negative electrode terminal, the current path from the current collector 40 to the shoulder 29 is shorter than the current path from the negative electrode lead connected to the bottom of the outer can to the shoulder. This reduces the electrical resistance of the cylindrical battery 10 when the shoulder 29 of the outer can 16 is used as the negative electrode terminal.

[0030] In the axial direction of the electrode body 14, at least a portion of the current collector plate 40 is preferably joined to the outermost peripheral portion 35 and the inner peripheral surface of the outer can 16 above the center position P1 of the electrode body 14 (the axial sealing body 17 side). This significantly reduces the electrical resistance of the cylindrical battery 10 when the shoulder portion 29 is used as the negative electrode terminal.

[0031] It is more preferable that the current collector plate 40 be joined to the outermost peripheral portion 35 and the inner peripheral surface of the outer can 16 above position P2, which is one-third of the length of the electrode body 14 from the upper end 14a on the sealing body 17 side, in the axial direction of the electrode body 14. This allows for a more significant reduction in the electrical resistance of the cylindrical battery 10 when the shoulder portion 29 is used as the negative electrode terminal.

[0032] In Figure 2, arrow A indicates the winding direction of the electrode body 14. If the length of the current collector plate 40 in the winding direction is 3 mm or more, it is easy to irradiate the laser beam to the area in the circumferential direction where the current collector plate 40 is located, making it possible to easily and reliably perform laser welding. Furthermore, if the axial length of the current collector plate 40 is 3 mm or more, it is easy to irradiate the laser beam to the area in the axial direction where the current collector plate 40 is located, making it easy and reliably perform laser welding. Furthermore, if the length of the current collector plate 40 in the winding direction is 1 / 3 or less of the circumferential length of the outermost peripheral surface of the electrode body 14, it is possible to smoothly insert the electrode body 14 into the outer can 16.

[0033] When the thickness of the current collector 40 is 30 μm or more and 200 μm or less, the electrode body 14 can be smoothly inserted into the outer can 16, and the current collector 40 can be smoothly welded to the outer can 16. The thickness of the current collector 40 is more preferably 50 μm or more and 150 μm or less.

[0034] 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.

[0035] For example, in the above embodiment, the current collector 40 is bonded only to both the negative electrode core portion (outermost peripheral surface-disposed portion 35) located on the outermost peripheral surface of the electrode assembly 14 and the inner peripheral surface of the tubular portion 39 of the outer can 16. However, as shown in Figure 3, i.e., the axial cross-sectional view of a modified cylindrical battery 110, the current collector 140 may have a first extension portion 141 that extends in the axial direction between the negative electrode core portion (outermost peripheral surface-disposed portion 35) located on the outermost peripheral surface of the electrode assembly 14 and the inner peripheral surface of the outer can 16, and a second extension portion 142 that extends radially inward from the lower end of the first extension portion 141 and extends along the inner surface of the can bottom.

[0036] In addition to joining the first extension portion 141 to the outermost peripheral surface arrangement portion 35 and the inner peripheral surface of the tubular portion 39, the second extension portion 142 may be joined to the bottom portion 31 of the outer can 16 by resistance welding, laser welding, or the like. This reduces the electrical resistance of the cylindrical battery 110 regardless of the connection structure of the battery pack. Therefore, a high-output, highly versatile cylindrical battery can be realized. In this case, it is preferable that the current collector plate 40 be joined to the outermost peripheral surface arrangement portion 35 and the inner peripheral surface of the outer can 16 at multiple positions, including positions above and below the center of the electrode body 14.

[0037] In the above embodiment, a cylindrical battery 10 has been described that can achieve high output by using the shoulder 29 of the outer can 16 as a negative electrode terminal. An external lead such as a bus bar may be directly joined to the shoulder 29, or a metal member may be joined to the shoulder 29 as an intermediate member between the shoulder 29 and the external lead. The shoulder 29 of the outer can 16 can also be used as a positive electrode terminal. That is, the shoulder 29 of the outer can 16 can be used as either a negative electrode or a positive electrode external terminal.

[0038] 10,110 Cylindrical battery, 11 Positive electrode, 12 Negative electrode, 13 Separator, 14 Electrode body, 14a Upper end of electrode body, 16 Outer can, 17 Sealing body, 18, 19, 25 Insulating plate, 20 Positive electrode lead, 22 Grooved portion, 23 Terminal plate, 24 Lower valve body, 26 Upper valve body, 27 Sealing plate, 27a Convex portion, 27b Vent, 28 Gasket, 29 Shoulder portion, 31 Bottom portion, 31a Lower surface of bottom portion, 33 Peripheral portion, 35 Outermost peripheral surface arrangement portion of negative electrode core body, 39 Cylindrical portion, 40,140 Current collecting plate, 141 First extension portion, 142 Second extension portion.

Claims

1. an electrode assembly in which a first electrode and a second electrode are wound with a separator interposed therebetween, and at least a portion of the outermost peripheral surface in the circumferential direction is formed by a core body of the first electrode; a cylindrical outer can with a bottom that houses the electrode assembly; a sealing body that closes the opening of the outer can; a current collector plate joined to both the core body located on the outermost peripheral surface and the inner peripheral surface of the outer can.

2. 2. The cylindrical battery according to claim 1, wherein the thickness of the current collector plate is 30 μm or more and 200 μm or less.

3. 3. The cylindrical battery according to claim 1, wherein the length of the current collector plate in the winding direction of the electrode assembly is 3 mm or more.

4. 3. The cylindrical battery according to claim 1, wherein the length of the current collector plate in the winding direction of the electrode body is equal to or less than one-third of the circumferential length of the outermost surface.

5. 3. The cylindrical battery according to claim 1, wherein at least a portion of the current collector plate is joined to both the core body and the inner circumferential surface of the outer can on the sealing body side of the center position of the electrode body in the axial direction of the electrode body.

6. 6. The cylindrical battery according to claim 5, wherein, in the axial direction of the electrode body, at least a portion of the current collector plate is joined to the inner circumferential surface of the core body and the outer can on the sealing body side of the electrode body at a position 1 / 3 of the length of the electrode body from the end of the electrode body on the sealing body side.

7. the current collector plate includes a first extension portion extending in the axial direction of the electrode body and a second extension portion extending along the inner surface of the bottom of the exterior can, The cylindrical battery according to claim 1 , wherein the second extension portion and the inner surface are joined together.